abdomen_New1.ppt

ANATOMY OF THE
ABDOMEN
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Outline
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Abdominal cavity
Anterolateral abdominal wall
Peritoneum and peritoneal cavity
Abdominal viscera
Digestive system viscera
Stomach
Small and large intestine
Pancreas
Liver
billiary tract
Spleen
Urinary system organs
Kidneys
Ureter
Posterior abdominal wall

Abdominal cavity
3
Ventral body cavity is divided into 2 parts
Thoracic cavity
Abdominopelvic cavity
Abdominopelvic cavity is further divided into
Abdominal cavity
Pelvic cavity

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Abdominal Cavity
5
A space bounded by abdominal walls,
diaphragm and pelvis
Forms the major part of abdominopelvic cavity
Most of the digestive and some urinary organs
reside in the abdominopelvic cavity
Enclosed anterolaterally by musculoaponeurotic
abdominal walls
Separated from thoracic cavity by diaphragm
Undercover of thoracic cage superiorly extend to
5th intercostal space
Lined with peritoneum

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© 2005 Elsevier

Regions of abdomen
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Clinicians subdivide abdomen into 9 regionsto
locate abdominal organs, pain sites, swelling or
incision
Delineated by 4 planes
Two horizontal
Subcostal plane: passing through inferior border of
10th costal cartilage
Transtubercular plane: passing through iliac tubercles
and body of L5 vertebra
Two vertical
Midclavicular planes:passing from midpoints of
clavicles to midinguinal points

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Regions of abdomen
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For general clinical descriptions, clinicians
divide abdomen into 4 quadrants defined by 2
planes
Transumbilical plane:passing through
umbilicus and disc between L3 and L4
vertebrae
Median plane:longitudinal plane dividing the
body into right and left halves

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Abdominal walls
11
Subdivided into
Anterior wall
Lateral walls
Posterior wall
Boundary between anterior and lateral walls is
indefinite thus called anterolateral wall

Anterolateral abdominal wall
12
Extends from thoracic cage to pelvis
Bounded
superiorly by cartilages of 7th -10th ribsand xiphoid
process
Inferiorly by inguinal ligament and pelvic bones
The wall consists of
skin
subcutaneous tissue
muscles and their aponeuroses
deep fascia
extraperitoneal fat and parietal peritoneum

Fascia of anterolateral abdominal wall
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The fascial layers from superficial to deep
include
Subcutaneous tissue (superficial fascia)
Inferior to umbilicus it is composed of two layers
Superficial fatty layer (Camper’s fascia)
Deep membranous layer (Scarpa’s fascia)
Investing fascia
Cover external aspects of the three muscle layers
Endoabdominal fascia
Lines internal aspect of abdominal wall

Abdominal wall layers
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Subcutaneous fascia
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Extraperitoneal fascia
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Lies deep to the muscles, it separates the
muscles from the peritoneum
Contains
Fat
blood vessels
organs and viscera such as kidneys and
pancreas which are retroperitoneal
Extends into the mesentery with blood
vessels, nerves and lymphatics

Muscles of anterolateral abdominal wall
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5 muscles: 3 flat and 2 vertical
Flat muscles
External oblique
Internal oblique
Transverse abdominal
Vertical muscles
Rectus abdominis
Pyramidalis

Externaloblique
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Superficial
Origin -outer surfaces of 5th-12th ribs
Fibers pass inferomedially and interdigitate with
serratus anterior
Insertion -linea alba,pubic tubercle,and iliac
crestvia aponeurosis
Inferior margin is thickened as fibrous band
between superior iliac spine and pubic tubercle
called inguinal ligament

Internal oblique
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Intermediate
Origin –thoracolumbar fascia, iliac crest and
inguinal ligament
Fibers fan out; upper fibers are perpendicular and
lower fibers are parallel to external oblique
Insertion –inferior borders of last 3 ribs,linea
alba,pubic crest

Transverse abdominal
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Inner most
Origin -inguinal ligament, thoracolumbar
fascia, inner surface of cartilages of last 6 ribs,
iliac crest
Fibers run horizontally
Insertion -linea alba, pubic crest

Rectus abdominis
21
Long, broad
Enclosed in rectus sheath
Origin -pubic crest and pubic symphysis
Insertion -xiphoid process and costal cartilages
of ribs 5 -7
The fibers do not run the length of the muscle
but run between 3 or more tendinous
intersections
Located at levels of xiphoid process, umbilicus and
halfway between the two

Pyramidalis
22
A small triangular muscle lies in rectus sheath
anterior to inferior part of rectus abdominis
Ends in linea alba and tenses it
Variable; absent in about 20% of people

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Rectus sheath
25
All 3 muscles end anteriorly in a sheet like
aponeuroses
Between midclavicular and midline it forms
rectus sheath, enclosing rectus abdominis
The aponeuroses interweave forming a
midline raphe called linea alba
extends from xiphoid process to pubic symphysis

Rectus sheath superior to the umbilicus
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The aponeuroses of all muscles are bilaminar
The decussation and interweaving of the
aponeuroses, occurring at the linea alba, are from
side to side and from superficial to deep
Superior to the umbilicus, both anterior and
posterior rectus sheaths are trilaminar
Anteriorly, there are the two layers of the aponeurosis of
the external oblique muscle and the superficial layer of
the aponeurosis of the internal oblique muscle
Posteriorly, there is the deep layer of the aponeurosis of
the internal oblique muscle and two layers of the
aponeurosis of the transversus abdominis muscle

Transverse section superior to the umbilicus
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Rectus sheath inferior to the umbilicus
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Approximately midway between the umbilicus
and the symphysis pubis, all of the
aponeuroses pass anterior to the rectus
abdominis muscle
the posterior rectus sheath gradually ends at the
arcuate line where the transversalis fascia comes
into contact with the posterior aspect of the
rectus abdominis muscle

Transverse section inferior to the umbilicus
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Functions and actions of muscles
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Support and protection
Compress abdominal viscera
Flex and rotate trunk

Nerves of anterolateral abdominal wall
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Thoracoabdominal nerves
Anterior rami of T7-T11
Subcostal nerve
Anterior ramus of T12
Iliohypogastric and ilioinguinal nerves
Anterior ramus of L1

Innervation of the anterior abdominal wall
32
•Intercostal nerves follow
the inferior slopes of the
ribs and continue over
the abdominal wall
•The abdominal muscles
in general are innervated
segmentallyin patterns
that reflect the overlying
dermatomes
•Remember: T10
supplies the umbilicus

Vessels of anterolateral abdominal wall
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Superior epigastric
Inferior epigastric
Superior and inferior epigastric arteries form
anastomoses
Deep and superficial circumflex iliac
Superficial epigastric
Posterior intercostal
Subcostal

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Surface anatomy
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Interior of anterolateral abdominal wall
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Covered by transversalis fascia, extraperitonial fat
and parietal peritoneum
5 umbilical peritoneal folds inferior to umbilicus
Median umbilical folds
Medial umbilical folds
Lateral umbilical folds
Peritoneal fossae
Supravesical
Medial inguinal
Lateral inguinal

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Inguinal area
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The area between anterior superior iliac spine
and pubic tubercle
A region where structures enter and exit
abdominal cavity
Weak area in the abdominal wall
Potential sites of herniation

Inguinal ligament and iliopubic tract
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Inguinal ligament
Inferior part of external oblique aponeurosis
Iliopubic tract
Thickened inferior margin of transversalis fascia
Run parallel and posterior to inguinal ligament
Both extend from anterior superior iliac spine to
pubic tubercle
Some fibers of inguinal ligament
attach to superior pubic ramus as lacunar ligamentand
run along pectin pubis as pectineal ligament
Arch superiorly to blend with contralateral aponeurosis
as reflected inguinal ligament

Inguinal canal
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Oblique passage through inferior part of
abdominal wall
the path taken by the testis during its descent
It is bounded by the deep and superficial
inguinal rings
4 cm long,inferomedially directed at inferior
margin of anterior abdominal wall parallel and
above to the lower half of the inguinal ligament
Contents
spermatic cord in males and round ligament of uterus
in females
genital branch of the genitofemoral nerveand
ilioinguinal nervein both

Inguinal canal: openings
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Deep (internal) ring
Evagination of transversalis fascia
Superficial (external) ring
Slit like opening between diagonal fibers of
external oblique aponeurosis
Lateral and medial margins –crura
The two rings do not overlap

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Deep inguinal ring and tranversalis fascia

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Superficial inguinal ring and the external oblique

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Inguinal canal: walls
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Anterior wall: formed by external oblique aponeurosis
Posterior wall: formed by transversalis fascia
Roof: formed by transversalis fascia (laterally), arches of
internal oblique and transverse abdominal (centrally) and
medial crus of external oblique aponeuroses (medially)
Floor: formed by iliopubic tract (laterally), inguinal ligament
(centrally) and lacunar ligament (medially)
The inguinal canal is contained in abdominal muscles
which will squeeze when the abdominal muscles contract.
Any increase in intrabdominal pressure (coughing,
defecation, lifting) will also tighten up the canal and
reduce the chance of a hernia developing

Inguinal canal: formation
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Formed in relation to descent of gonads(testes or ovary)
during fetal development
Testes develop in lumbar regions
They pass through inguinal canals into scrotum just
before birth
Before the descent of the gonads a cord of tissue –the
gubernaculum (Latin = helm or guide) descends from the
gonad into the primitive scrotum or labia
Later, out pouching of peritoneum (processus vaginalis)
follows gubernaculum and evaginates anterior abdominal
wall to form inguinal canal
A tubular extension of the peritoneal cavity (processus vaginalis)
projects alongside the gubernaculum into the labioscrotal swelling

Inguinal canal: formation
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In man the testis along with its nerves and blood vessels
and duct (ductus deferens) descends into the scrotum
alongside the processus vaginalis guided by the
gubernaculum.
In women, the ovaries do not descend; gubernaculum
becomes the round ligament of the uterus
The inguinal canal is the passage through the
abdominal wall created by the processus vaginalis
Normally the processus vaginalis obliterates
If the processus vaginalis does not obliterate a
weakness exists in the anterior abdominal wall which
may lead to an indirect inguinal hernia
Note the inguinal canal is surrounded by muscle

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Inguinal hernias
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Inguinal hernia is the protrusion of a part of the
peritoneal sac,with or without abdominal
contents, into the groin
A hernia may enter the inguinal canal either:
indirectly,through the deep inguinal ring or
directly,through the posterior wall of the inguinal
canal
An inguinal hernia is therefore classified as
either an indirectinguinalherniaor direct
inguinal hernia

Indirect inguinal hernia
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Common
congenital
Men > women
Occurs because part, or all, of the embryonic processus
vaginalis remains open or patent
The protruding peritoneal sac enters the inguinal canal by
passing through the deep inguinal ring, just lateral to the
inferior epigastric vessels
The extent of its excursion down the inguinal canal
depends on the amount of processus vaginalis that
remains patent
If the entire processus vaginalis remains patent, the
peritoneal sac may traverse the length of the canal, exit
the superficial inguinal ring, and continue into the scrotum
(or the labia in women)

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Direct Inguinal hernia
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A direct inguinal herniapushes directly
through the posterior wall of the canal and
causes a bulge
Very occasionally it may push through the
external ring and into the scrotum but in general
a hernia in the scrotum is an indirect hernia
Direct inguinal hernias are associated with age,
weak muscles and obesity

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Hernias
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The intestinal contents within the hernia may
become obstructed
The blood supply to the trapped bowel may be
compromised and the bowel may become
ischaemic and infarct (= die)
Infarcted or obstructed bowel is a surgical
emergency

Spermatic cord
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Contains structures run to and from testis and suspends
testis in scrotum
Fascial coverings
Internal spermatic fascia
Cremasteric fascia
External spermatic fascia
Constituents
Ductus deferens
Testicular artery
Artery of ductus deferens
Cremasteric artery
Pampiniform venous plexus
Nerves
Lymphatic vessels
Vestige of processus vaginalis

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Scrotum
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Cutaneous sac consisting of two layers
Skin
Dartos fascia
Skin is heavily pigmented and covered with
sparse hairs
The paired testes lie suspended in the scrotum
A midline septum divides the scrotum into right
and left halves, one compartment for each
testis

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Scrotum: temperature regulation
62The location of testes appears to make them vulnerable to
injury
However, viable sperm cannot be produced at core body
temperature
The superficial location of the scrotum provides a
temperature which is about one degree cooler
The scrotum also responds to temperature changes
When it is cold, the testes are draw closer to the warmth of the body
and the scrotum becomes shorter and heavily wrinkled to reduce heat
loss
When it is warm, the scrotal skin is flaccid and loose to increase
cooling, and the testes hang lower
These changes reflect the activity of the two sets of muscles
Dartos
Cremaster

Scrotum: neurovasculature
Arteries
Ant and post scrotal branches of perineal and
pudendal arteries
Cremasteric artery
Nerves
Genital branch of genitofemoral nerve
Anterior and posterior scrotal nerves
Perineal branches of posterior femoral cutaneous
nerve
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Testes
Each testes is approximately 4 cm longand
2.5 cm in diameter
It is surrounded by two tunics
Tunica vaginalis: outer; derived from the
peritoneum
Tunica albuginea: deep; fibrous capsule
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Testes
Septa extending from the tunica albuginia divide the testis
into 250 -300 wedge shaped compartments or lobules
Each lobule contains 1-4 seminiferous tubules
site of sperm production
The seminiferous tubules of each lobule converge to form a
straight tubules
conveys sperm into the rete testis
The rete testis is a tubular network from which the sperm
leave via the efferent ductules
Sperm leaving the efferent ductules enter the epididymis
which is located on the external surface of the testis
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Testes : neurovasculature
The long testicular arteries, which branch from
the abdominal aorta, supply the testes
Testicular veinsarise from a network called
pampiniform plexusthat surrounds the testicular
artery
The plexus absorbs heat from the arterial blood,cooling it before
it enters the testes. Thus, it provides an additional avenue for
maintaining the testes at their cool homeostatic temperature
The testes are served by both divisions of the
autonomic nervous system
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Peritoneum and peritoneal cavity
72
All ventral body cavities contain serous
membranes
The peritoneum of the abdominal cavity is the
most extensiveserous membrane of the body
Consists of a layer of simple squamous epithelium
(mesothelium)with an underlying supporting layer
of connective tissue
Two layers
visceral peritoneum:covers the external surface of most
digestive organs
parietal peritoneum:lines the walls of the
abdominopelvic cavity

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Peritoneal cavity
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Between the two layers is the peritoneal cavity,
a slit like potential space containing fluid
secreted by the serous membranes
The serous fluid lubricates the mobile digestive
organs, allowing them to glide easily across one
another as they carry out their digestive
activities

peritoneal and retroperitoneal organs
76
In early embryo the peritoneum is a large sac that lines the
walls of abdominal cavity
The primordia of viscera are located outside this sac in
extraperitoneal tissue
As the viscera develop, they protrude into the peritoneal sac
to varying degrees
Some organs protrude only slightly are called
retroperitoneal
E.g. kidneys
Others protrude further into peritoneal sac and are covered
on each side with peritoneum
E.g. ascending colon
Some other organs protrude completely into the sac are
completely covered with visceral peritoneum
E.g.. Stomach, jejunum

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When an organ protrudes into peritoneal sac, it
takes its nerves and vessels with it
As the viscera enlarge, the peritoneal cavity is
obliteratedalmost completely
Peritoneal cavity is a potential space
In men the peritoneal cavity is closed. In
women it is pierced by the Fallopian tubes
which, via the uterus and vagina, offer a
possible route of infection into the peritoneal
cavity

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Peritoneal folds
79
Peritoneum contains large folds that weave
between viscera
The folds binds organs to each other and to
the walls of abdominal cavity

Greater omentum
80
Drapes over transverse colon and coils of small
intestine like apron
Double sheet folds back upon itself; four-
layered
From attachments along greater curvature of
stomach and duodenumit extends downward
anterior to small intestine and turns upward and
attaches to transverse colon

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Lesser omentum
82
Arises as two folds in serosa of stomach and
duodenum and attach to liver
Extends from inferior portion of liver to lesser
curve of stomach and 1
st
part of duodenum
The lesser omentum is the anterior border of the
lesser sac
The lesser omentum contains the major hepatic
vessels –bile duct, portal vein and hepatic artery-
and the gastric vessels
Its free edge forms the boundary between the
greater and lesser sacs at the omental foramen

83

84

Falciform ligament
85Attaches liver to anterior abdominal wall

Mesocolon
86
Binds large intestine to posterior abdominal
wall
Transverse mesocolon;binds transverse colon
to posterior abdominal wall
Sigmoid mesocolon;supports the sigmoid colon

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Mesentery
88
A mesentery is a double layerof peritoneum
that encloses an organ and connects it to the
body wall
Mesenteries provide routesfor blood vessels,
lymphatics and nerves to reach the digestive
viscera
Mesenteries also suspend the visceral organs
in place as well as serving as a site for fat
storage

Mesentery
89
Not all alimentary canal organs are suspended with
the peritoneal cavity by a mesentery
Some organs adhere to the dorsal abdominal wall
Organs that adhere to the dorsal abdominal wall
lose their mesentery and lie posterior to the
peritoneum
These organs, include duodenum, pancreasand parts of
the large intestineare called retro-peritoneal organs
Digestive organs like the stomach that keep their
mesentery and remain in the peritoneal cavity are called
peritoneal organs

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Lesser
sac

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Subdivisions of peritoneal cavity
93
Greater omentum, transverse colon and
transverse mesocolon divides peritoneal cavity
into supracolic and infracolic compartments

Supracolic compartment
94
Divided into 2 by falciform ligament
Subphrenic recessesbetween diaphragm and
liver
Hepatorenal recessbetween right lobe of liver
and right kidney

Infracolic compartment
95
Divided into right and left infracolic spacesby
mesentery of small intestine
Paracolic gutterson each side of ascending
and descending colons
Paravertebral gutteron each side of vertebral
column

Omental bursa (lesser sac)
96
Recess of peritoneal cavity between stomach
and posterior abdominal wall
Inferior recess: extension between layers of
greater omentum; shut off by adhesion of the
layers
Communicate with main peritoneal cavity
(greater sac) through omental foramen

97

The digestive system
98
The digestive system performs 6 basic
processes:
Ingestion:taking in food
Secretion:water, acid, buffers and enzymes
Mixing and propulsion:mix food and secretions and
move materials
Digestion:break down food into nutrient molecules
Absorption: entrance of the nutrient molecules into the
bloodstream
Defecation:removal of indigestible remains

Organsof the digestive system
99
Two groups of organs
alimentary canal or gastrointestinal (GI) tract
accessory digestive organs
The alimentary canal is the continuous muscular tube
that extends from mouth to anus through the ventral body
cavity
Is about 9 m
Food pass through it and broken down
It is inside the body but separates its contents from the rest of the
body allowing the food we eat to be processed before being
absorbed and used by the body.
Provide space for digestion and absorption
The accessory organs are related to GIT
produce saliva, bile and digestive enzymesthat contribute to the
breakdown of foodstuffs

100

Organs
101
The organs of the GIT
Mouth
Pharynx
Esophagus
Stomach
Small and large intestine
The accessory digestive organs
Teeth
Tongue
Salivary glands
Gallbladder
Liver
Pancreas

Histology of the GI tract
102
Each part of the alimentary tract has a highly specialised
functionbut the basic structure of the tube is the same
throughout its length
From the esophagus to the anal canal, the walls of every
organ of the GIT is made up of the same four basic
layers or tunics
From internal to external the four layers are
Mucosa
Submucosa
Muscularis Externa
Serosa
Each tunic contains a predominant tissue type that plays
a specific role in food breakdown
Histology is the study of tissue and cell under
microscopic

103

Mucosa
104
Mucosa is a mucous membrane that lines the
lumen of GI tract
Major functions
Secretion of mucus, digestive enzymes and
hormones
Absorptionof digestion end products to blood and
lymph
Protective barrier

Mucosa: sub layers
105
Typical digestive mucosa consists of three sub
layers
epithelium
lamina propria
muscularis mucosae

Epithelium
106
The epithelium is
nonkeratinized stratified squamousin mouth,
pharynx, esophagus and anal canal (protective)
simple columnar epitheliumwith mucus secreting
goblet cells in stomach and intestine (secretion
and absorption)
Cell types
Absorptive cells
Exocrine cells:secrete mucus and fluid
Enteroendocrine cells:secrete hormones

Lamina propria
107
Loose areolar connective tissue
Contains many blood and lymphatic vessels
Its capillaries nourish the epithelium and absorb
digested nutrients
Supports epithelium and binds it to muscularis
mucosae
Its isolated lymph nodules are part of the mucosa
associated lymphatic tissue (MALT);defense
against pathogens
Large collections of lymph nodules occur at
strategic locations; pharynx (tonsils) and appendix

Muscularis mucosae
108
Isascantlayerofsmoothmusclecellsthat
produceslocalmovementsandfoldingofthe
mucosa
Thetwitchingofthismusclelayerdislodgesfood
particlesthathaveadheredtothemucosa
Inthesmallintestine,itthrowsthemucosainto
aseriesofsmallfoldsthatimmenselyincrease
itssurfacearea

Basic mucosal forms
109
Protective: in oral cavity, pharynx, esophagus
and anal canal
Epithelium is stratified squamous
Secretory:in stomach
Consists of tubular glands
Absorptive:small intestine
Mucosa forms villi
Absorptive and protective:lines large intestine
Arranged into tubular glands with cells specialized
for water absorption and mucus-secreting cells

Submucosa
110
Composed of a moderately dense collagenous
tissue
Binds mucosa to muscularis
Contains many blood vessels, lymphatic
vessels, lymph nodules, glands,and nerve
fibers
Consists of submucosal (Meissner’s) plexus
formed by nerve fibres and ganglion cells and controls
glandular secretion
Its rich supply of elastic fibersenables the
stomach to regain its normal shape after storing
a large meal

Muscularis Externa
111
Main muscle coat
Generally, consists of inner circular muscle and outer
longitudinal muscle layers
Is responsible for segmentation and peristalsis
In mouth, pharynx, superior and middle esophagus, and
external anal sphincter contains skeletal muscle
The rest contains smooth muscle
Between the two layers are myenteric (Auerbach’s) plexus
It mixes and propels foodstuffs along the digestive tract
In several places along the GI tract, the circular layer
thickens to form sphincters
Sphincters act as valves to prevent backflow and control
food passage from one organ to the next

Serosa
112
Is a protective outermost layer of
interaperitoneal organ
In abdominal cavity it is termed as visceral
peritoneum
Formed of areolar connective tissue lined by
simple squamous epithelium (mesothelium)

Serosa
113
In the esophagus, which is located in thoracic
cavity, the serosa is replaced by an adventitia
The adventitia is a fibrous connective tissuethat
binds the esophagus to surrounding structures
Retroperitoneal organshave both a serosa(on the
side facing the peritoneal cavity) and an adventitia
(on the side abutting the dorsal body wall)

Esophagus
Carry food
Propulsion of food from
laryngopharynx to stomach
~25cm long,mainly in thoracic
cavity
Last 2-3 cmin the abdominal
cavity
Mucosa of thick stratified
squamous epithelium
Suited to constant abrasion
Germinal layer at basement
membrane forms new cells,
dead cells at lumen
114

Intrabdominal esophagus
The abdominal esophagus
represents the short part of the
esophagus located in the
abdominal cavity
It emerges through the right
crus of the diaphragm,usually
at the level of vertebra T10
It passes from the
oesophageal hiatusto the
stomach just left of the
midline. It is accompanied by
the vagus nerve
Joins stomach at
gastroesophageal junction
Here epithelium changes from
stratified squamous to
columnar
115

The Stomach
116
Thestomachisinvolvedinthewholerangeof
digestiveactivities
Itservesasaholdingareaforingestedfood
Breaksdownfoodfurtherchemicallyandmechanically
Itdeliverschymetothesmallintestineatacontrolledrate
Thestomachliesintheupperleftquadrantofthe
abdominalcavity
Thoughrelativelyfixedatbothends,itisfreeto
moveinbetween

The Stomach: Gross Anatomy
117
The stomach varies from 6 to 10 inchesin
length, but its diameter and volume depend on
how much food it contains
Emptymay contain 50 mlbut can expand to
hold about 4 liters of food
When empty, the stomach collapses inward,
throwing its mucosa into large, longitudinal
folds called rugae

The Stomach: Gross Anatomy
118
4 major region of the stomach
Cardia:surrounding cardial orifice
Fundus:dilated superior part
Body: main region
pyloric region:funnel shaped, its wide partpyloric
antrumleads into pyloric canal,its narrow part
Pylorus -distal sphinteric region, controls discharge of stomach
contents through pyloric orifice into doudenum
2 curvatures
greater and lesser curvatures

The stomach: region
The cardia
(because it is near
the heart)
The greater
curvature is to the
left, the lesser
curvature on the
right
Different parts of
the stomach have
different highly
specialised
functions
119

120

The Stomach: Blood supply
121
Rich blood supply
From celiac trunk and its branches
The arterial arch on the lesser curvatureis formed by
left gastric artery
right gastric artery
The arterial arch on the greater curvatureis formed by
the right and the left gastro-omental (gastroepiploic) arteries
The anastomoses between the branches of these arterial
arches take place in the submucous coat two thirds of
the distance from the lesser to greater curvature
Fundus and upper body receive blood from short and
posterior gasteric arteries

The Stomach: Blood supply
122
Gastric veins parallel the arteries
Left and right gastric veinsdrain into portal
vein
Short gastric veins and left gastro-omental
veins drain into splenic vein
Right gastro-omental vein drain into superior
mesenteric vein

123

The Stomach: innervation
124
Parasympathetic –anterior vagal trunk (mainly
from left vagus nerve) and posterior vagal
trunk (mainly from right vagus nerve)
Sympathetic –T6-T9 through greater
splanchnic nerves

Stomach: Microscopic Anatomy
125
The stomach wall exhibits the four tunics of
most of the alimentary canal but its muscularis
and mucosa are modified for the special roles
of stomach
The muscularis externahas an extra obliquelayer
of muscle that enables it to mix, churn and
pummel food
The epithelium lining the stomach mucosa is
simple columnar epitheliumcomposed entirely of
goblet cells, which produce a protective coating of
mucus

Stomach: Microscopic Anatomy
126
The four tunics
typical of the
alimentary canal
Mucosa
Submucosa
Muscularis
Externa
Serosa

Stomach: mucosa
127
has tubular glandular form
Epithelium dotted with millions of deep gastric pits,which lead to the
gastric glands
Branched tubular glandsempty into gastric pit
Collectively produce gastric juice
These glands are found throughout the stomach but vary depending
on site
The glands of the stomach body are substantially larger and produce
the majority of the stomach secretions
4 main secretory cells:
Mucous neck cells
Parietal cells
Chief cells
Enteroendocrinecells
Lamina propria: loose CT with small lymphoid aggregation
Muscularis mucosae lie beneath gastric glands

128

Stomach: mucosa
129
Mucus neck cells
In upper part of gland
produce a different type of mucusfrom that
secreted by the mucus secreting cells of the
surface epithelium
The special function of this unique mucus is not
yet understood

Stomach: mucosa
131
Chief cells
occur mainly in the basal regions of the gastric
glands
produce pepsinogen,the inactive form of the
protein-digesting enzyme pepsin
Pepsinogen is activated by HCl
Also secrete small amounts of lipases

Stomach: mucosa
132
Enteroendocrine cells
In base of gland
release a variety of hormonesdirectly into the
lamina propria
Reverse polarity–secrete hormones into the
blood space rather than the GI lumen
These products diffuse into capillaries and
ultimately influence several digestive system
target organs which regulate stomach secretion
and mobility

Mucosal Barrier
133
Gastric juice highly concentrated acid
Under such harsh conditions the stomach
must protect itself from self digestion with a
mucosal barrier
Bicarbonate rich mucusis on the stomach wall
Epithelial cells are joined by tight junctions
Glandular cells are impermeable to HCl
Surface epithelium is replaced every 3 to 6 days

Other layers of stomach
134
Submucosa
relativelyloose,infiltratedbylymphoidcells
Muscularis
has 3 layers
comprises inner circular and outer longitudinal but inner circular is
reinforced by a further inner oblique layer in body
Circular
Longitudinal
Oblique (innermost)
Enables the stomach to churn and mix the food into chyme
Circular muscle layer thickened at the pylorus to form the
sphincter
Serosa
thin & covered by mesothelium

Gastroduodenal junction
135
Atpyloricsphinctermucosachange
fromglandulartovillousarrangement
Pyloricsphincterconsistsofthickened
circularlayer

The Small Intestine
136
Major digestive organ
In the small intestine, usable food is finally
prepared for its journey into the cells of the
body
Here digestion is completed and virtually all
absorption occurs
However, this vital function cannot be
accomplished without the aid of secretions
from the liver (bile) and pancreas (digestive
enzymes)

The Small Intestine
137
The small intestine is a convoluted tube
extending from the pyloric sphincter in the
epigastric region to the iliocecal valvewhere it
joins the large intestine
It is the longest part of the alimentary tube, but its
diameter is only about 2.5 cm
In the cadaver, the small intestine is 6 -7 meterslong
because of loss of muscle tone, while it is only 2 -4
meters long in the living individual
The small intestine has three subdivisions
Duodenum
Jejunum
Ileum

The Small Intestine: duodenum
138
The relatively immovable duodenum which
curves about the head of the pancreas
C-shaped
about 10 inches long
Relation
Behind: aorta, IVC
In front: transverse colon
Looping over its 4
th
part is the superior mesenteric
artery and vein

139

Parts of duodenum
First part
Duodenal cap or bulb
(where the ulcers occur)
Second (descending) part
where the bile duct and
pancreatic duct join the
duodenum through the
ampulla of Vater
Third part (inferior or
transverse)
Fourth part (ascending)
140

The duodenum
141
features
Bile duct
Main pancreatic duct
Hepatopancreatic ampulla
Major duodenal papilla
The bile duct,delivering bile from the liver
The main pancreatic duct,carries pancreatic
juice from the pancreas
The hepatopancreatic ampullais where these
two ducts unite in the wall of the duodenum
The papillais where this sphincter enters the
duodenum

142

The Small Intestine: jejunum
143
Mainly in left upper quadrant
Responsible for absorbing most of the intestinal
contents
2 ½ meters long (8 ft)
extends from the duodenum to the
ileum
twists back and forth within the
abdominal cavity

The Small Intestine: ileum
144
More in lower right side of abdomen
3 ½ meters(12 ft) in length
No sharp division from the jejunum
but ileum has
thicker wall
larger diameter
supplied by less frequent terminal vessels
Slightly different histology; Otherwise very similar
structure
Specialised function is to absorb bile salts and
vitamin B12
Joins the caecum at the ileocaecal valve

145

The Small Intestine
146
The jejunum and ileum hang in coils
in the central and lower part of the
abdominal cavity
The jejunum and ileum are
suspended from the posterior
abdominal wall by the fan shaped
mesentery

The Small Intestine: innervation
147
Nerve fibers serving the small intestine include
the parasympathetics from the vagus nerves
and sympathetics from the long splanchic
nerves
These are relayed through the superior
mesenteric and celiac plexus

The Small Intestine: blood supply
148
The arterial supply is primarily from the superior
mesenteric artery
The veins run parallel to the arteries and
typically drain into the superior mesenteric vein
From the mesenteric vein, the nutrient rich
venous blood from the small intestine drains into
the hepatic portal veinwhich carries it to the liver

Small Intestine: Microscopic Anatomy
149
The four tunics of the digestive tract are
modified in the small intestine by variations in
mucosa and sub-mucosa
The small intestine is highly adapted for
nutrient absorption
Its length provides a huge surface area for
absorption

Small Intestine: Microscopic Anatomy
150
There are three structural modifications which
increase the surface area for absorption
Plicae circulares
Villi
Microvilli
Structural modifications increase the intestinal
surface area tremendously
It is estimated that the surface area of the small
intestine is equal to 200 m
2
Most absorption occurs in the proximal part of the
small intestine, with these structural modifications
decreasing toward the distal end

151

Small Intestine: Microscopic Anatomy
152
The circular folds or plicae circularis
deep permanent folds of the mucosa and
submucosa
nearly 1 cm tall
The folds force chyme to spiral through
the lumen, slowing its movement and
allowing time for full nutrient absorption

Small Intestine: mucosa
153
The epithelium of the mucosa is largely simple
columnar epitheliumserving as absorptive cells
The cells are bound by tight junctions and richly
endowed with microvilli
Also present are many mucus-secreting goblet
cells
Scattered among the epithelial cells of the wall are
T cells called intraepithelial lymphocytes
These T cells provide an immunological component
Finally, there scattered enteroendocrine cells which
are the source of secretin and cholecystokinin

Enterocyte
Predominant type
Tall columnar with basal nuclei
Involved in digestion and absorption
Specialised for absorptionof nutrients across luminal
membrane to the basal membrane, and from there into
capillaries or lacteals
Luminal surface is covered by mucus which protect
against auto digestion
At apex of cells are many microvilli
Protrusion of cell membrane
Increase surface area
Constitute striated border of light microscopy
Enterocytes are tightly bound near luminal surface
by junctional complex
Short life-span of a few days
154

155
Goblet cells
Scattered among enterocytes
Less abundant in duodenum and increase
towards ileum
Produce mucus

156

Small Intestine: mucosa
157
Villi
finger like projections of the mucosa
~1 mm tall
give a velvety textureto the mucosa
The epithelial cells of the villi are chiefly
absorptive columnar cells

158
Central core of lamina propria containscapillary
bed and a wide lymphatic capillarycalled lacteal
Digested food is absorbed through the
epithelial cells into both the capillary blood
and the lacteal
Small smooth muscle in villi allows change in
shape and size
Villi become gradually narrower and shorteralong
the length of the small intestine

Small Intestine: mucosa
159
Microvilli
tiny projectionsof the plasma membrane of the
absorptive cells of the mucosa
It gives the mucosal surface a fuzzyappearance
sometimes called a brush border
Beside increasing the absorptive surface, the
plasma membrane of the microvilli bear enzymes
referred to as brush border enzymes
These enzymes complete the final stages of
digestion of carbohydrates and proteinsin the
small intestine

Small Intestine: mucosa
160
Between villi the mucosa is studded with pits
that lead into tubular intestinal glands called
intestinal crypts or crypts of Lieberkuhn
The epithelial cells that line these crypts secrete
intestinal juice
Intestinal juice is a watery mixture containing
mucus that serves as a carrier fluid for
absorption of nutrients from chyme

Small Intestine: mucosa
161
Located deep on the crypts are specialized
secretory cells called Paneth cells
Packed with eosinophilic granules
Exocrine protein secreting cells, secrete
lysozyme;an antibacterial enzyme
The number of crypts decreases along the length
of the wall of the small intestine, but the number of
goblet cells becomes more abundant

162

Small Intestine: mucosa
163
M (microfold) cells
Specialized epithelial cells overlying
lymphoid follicles of peyer’s patches
Characterized by numerous membrane
invaginations
Endocytose antigen and transport to
lymphoid cells
Basement membrane under M cells is
discontinuous to facilitate transit

Small Intestine: mucosa
164
Stem cells
The various epithelial cells arise from rapidly dividing
stem cells at the base of the crypts
Stem cells divide in intestinal crypts and migrate up
to the villi to replace damaged and dying cells –the
‘epithelial escalatory’
The daughter cells gradually migrate up the villi
where they are shed from the villus tips
In this way the villus of the epithelium is renewed
every three to six days

Small Intestine: submucosa
165
typical areolar connective tissue
it contains both individual and aggregated
lymphoid follicles (Peyer’s patches)
Peyer’s patches increase in abundance toward
the endof the small intestine, reflecting the fact
that the large intestine contains huge numbers
of bacteria that must be prevented from
entering the bloodstream

Small Intestine: submucosa
166
A set of elaborated mucus-secreting duodenal
glands (Brunner’s glands)is found in the
submucosa of the duodenum only
These glands produce an alkaline (bicarbonate-
rich) mucus that helps neutralize the acidic
chyme moving in from the stomach
When this protective mucus barrier is
inadequate, the intestinal wall is eroded and
duodenal ulcers results

Small Intestine: muscularis & serosa
167
The muscularis is typical and bilayered
Except for the bulk of the duodenum, which is
retroperitoneal and has an adventitia, the
external intestinal surface is covered by
visceral peritoneum (serosa)

The Liver and Gallbladder
168
The liver and gallbladder are accessory organs
associated with the small intestine
Liver Functions
Detoxification
Destruction of spent RBCs
Synthesis of bile
Synthesis of plasma proteins
Metabolic activities
The gallbladder is a storage site for bile

The Liver: gross anatomy
169
The reddish, blood rich liver is the
largest glandin the body weighing
about 1.4 kgin the average adult
Above the liver is the diaphragm, to its left is
the stomach and below is the transverse colon
The anatomically “busy” areaof the liver is
underneath on its visceral surface

The Liver: gross anatomy
170
Shaped like a wedge, it occupies most of the
right hypochondriac and epigastric regions
extending farther to the right of the body
midline than the left
Located under the diaphragm, the liver lies
almost entirely within the rib cage
The location of the liver within the rib cage offers
this organ some degree of protection

171

172

173

The Liver: gross anatomy
174
The liver has four lobes; right, left, caudate
and quadrate
Falciform ligamentseparates the right and left
lobes anteriorly and suspends the liver from
the diaphragm
Running along the free inferior edge of
the falciform ligament is the ligamentum
teresa remnant of the fetal umbilical
vein

The Liver: gross anatomy
175
Except for the superiormost liver area,
which is fused to the diaphragm, the
entire liver is enclosed by a serosa
(visceral peritoneum)
The lesser omentum,anchors the liver
to the lesser curvature of the stomach

176

The Liver: gross anatomy
177
The hepatic arteryand portal vein,
enter the liver at the porta hepatis
The common bile duct,which runs
inferiorly from the liver, travels
through the lesser omentum

The Liver: Microscopic Anatomy
178
Stroma
External surface is invested by thin collagenous
capsule=Glisson’s capsule
Thick at hilum, surround vessels and ducts to
interior
Fine meshwork of reticular fibers radiate from
this CT, support liver cells

The Liver: Microscopic Anatomy
179
Liver lobule
Liver parenchymal cells (hepatocytes) are arranged
into lobules
structural & functional units called liver lobules
around one million liver lobules
Each lobule is roughly hexagonal in shape
Bounded by thin septa of collagenous tissue
Angle of lobule are portal tracts
Terminal braches of portal vein and hepatic artery and
bile duct
Center of lobule is a centrolobular venule (central vein)

180

The Liver: Microscopic Anatomy
181
Liver parenchyma
Hepatocytes or liver cells are organized to radiate
out from a central vein running the length of the
longitudinal axis of the lobule
Hepatocytes form flat anastomosing plates
Plates are directed from periphery of lobules to its
center
Spaces between plates contain capillaries=liver
sinusoids
Sinusoids are lined by discontinuous layers of cells which do
not rest on basement membrane
Endothelial cells are separated from hepatocytes by a narrow
space = space of Disse,which drain to lymphatics

The Liver Lobule
182
At each of the six corners of a lobule is a portal
triadso named because three basic structures
are always present there: A branch of
hepatic artery
portal vein
bile duct

The Liver Lobule
183
blood comes from the hepatic artery(20%)and
portal vein(80%)
The hepatic artery supplies oxygen rich arterial
blood to the liver
The hepatic vein carries blood laden with nutrients
from the digestive viscera
A bile duct carry secreted bile toward the
common bile duct and ultimately to the
duodenum

The Liver Lobule
184

The Liver Lobule
185
Hepatocytes form into plates one-cell thick,
divided by sinusoidal blood channels 9-12μmin
diameter
The portal triad supplies the nutrient-and
oxygen-rich blood for processing and is the route
for the drainage of bile
Sinusoids drain into the thin-walled central vein
Central vein sublobular veins collecting
veins hepatic veins circulation
Bile travels in the opposite directionto sinusoidal
blood between hepatocyte layers
Composition of blood entering the lobule modified by
hepatocytes and macrophages

186

The Liver Sinusoid
187
Between the hepatocyte plates are enlarged,
very leaky capillaries,the liver sinusoids
Blood from both the hepatic portal vein and the
hepatic artery percolates from the triad regions
through these sinusoids and empties into the
central vein
From the central vein blood eventually enters
the hepatic veins, which drain the liver, and
empty into the inferior vena cava
Inside the sinusoids are star shaped hepatic
macrophages, also called Kupffer cells,which
remove debris such as bacteria and worn-out
blood cells

The Hepatocyte
~80% of the mass of the liver
Metabolic factories
form and secrete bile
store glycogenand buffer blood glucose
synthesize urea
metabolize cholesteroland fat
synthesize plasma proteins
detoxifymany drugs and other poisons
process several steroid hormonesand vitamin D
188

The Hepatocyte
189
Extensive rough endoplasmic
reticulum
–Protein synthesis
Smooth ER
–For hormone processing
and detoxification
Golgi body and lysosomes
–for the formation of bile
Mitochondria
–For oxidation
Microvilli into the Space of
Disse
Large nucleus

190
Hepatocytes are exposed on each side to
sinusoids which are lined by discontinuous layer
of cells
Via gaps in sinusoid lining the space of Disseis
continuous with sinusoid lumen thus bathing
hepatocyte surface with blood
Numerous microvilli extend from hepatocytes into
the space of Disse, increasing surface area for
metabolic exchange

Liver cell showing relation between sinusoid,
space of Disse and canaliculus
191

Hepatic vasculature
192
Liver receives blood from 2 sources
Portal vein (80%)-carries oxygen poor nutrient rich blood
from abdominal viscera
Hepatic artery(20%)-supplies oxygen rich blood
Portal vein system
Portal veinbranches and send portal venuleto portal triads
Portal venules branch into distributing veinsthat run around
periphery of lobule
From distributing veins small inlet venulesempty into
sinusoids
Sinusoids converge in center of lobule to form central vein
Central vein leaves lobule and merge with sub lobular veins
Sub lobular veins converge to form hepatic veins

193
Arterial system
Hepatic artery branch to form interlobular arteries
Interlobular arteries form inlet arteriolesthat ends in
sinusoids
NB: arterial and venous blood mixes in sinusoids
Biliary system
Liver cells secrete bile into bile canaliculisituated
between plasma membranes of adjacent hepatocytes
The canalicular system drains to bile collecting ducts
Collecting ducts merge and form trabecular ducts
which emerge from liver as right and left hepatic ducts
The two hepatic ducts join to form common hepatic
ductwhich join cystic duct to form common bile duct
Hepatic, cystic and common bile ducts are lined by
simple columnar epithelium

194

195
Portal triads
Consists of 3 main structures
Terminal branch of hepatic portal vein
Terminal branch of hepatic artery
Bile collecting duct
The 3 are found in portal tracts
Lymphatics are also present in portal tracts

Portal vein, hepatic artery,
hepatic veins and bile duct
196

Nerves of the liver
197
derived from the left vagusand sympathetic
nerves, enter at the porta and accompany the
vessels and ducts to the liver lobule
functions:
1.Control tone in the blood vessels
2.Influence several metabolic and hormone-
releasing processes

Liver regeneration
198
Liver cells have extraordinary capacityfor
regeneration
Loss of hepatic tissue triggers cell division and
restore original mass
Regenerated tissue is similar to the removed
but if there is repeated damage, regeneration
and production of CT occurs simultaneously
which results in disorganization of liver
structure=cirrhosis

The Gallbladder
199
The gallbladder is a thin-walled,
green muscular sac
Pear-shaped muscular sac
Store and concentrate bile
~10cm long
It snuggles in a shallow fossa on the
ventral surface of the liver

200

The Gallbladder
201
Expels bile when acidic chyme enters the
duodenum or as a result of cholecystokinin
release
When empty, its mucosa adopts the ridge like
folds or rugae
Its muscular walls can contract to expel its
contents into the cystic duct which then flows
into the bile duct
Like most of the liver it is covered by visceral
peritoneum

The Gallbladder
202
When digestion is not occurring, the
hepatopancreatic sphincter is tightly closed
Bile then backs up the cystic duct into the
gallbladder where it is stored until needed
Right and left hepatic ducts join to make the common
hepatic duct
When joined by the cystic duct it becomes the common
bile duct
The bile duct, after descending posterior to the 1st part
of the duodenum and the accessory pancreatic duct, is
joined by the main pancreatic duct; these open on the
duodenal papilla

Gall bladder: microscopic anatomy
203
Mucosa
In non distended state is thrown into many folds
Lined by simple columnar epithelium
Submucosa
Loose, rich in elastic fibers,blood and lymph vessels
Muscular layer
Thin, fibers are disposed obliquely
In neck region, epithelium invaginate and form mucous
glands
Serosa/adventitia
Binds superior surface to liver (adventitia)
Opposite surface is lined by serosa (peritoneum)
Cystic duct
Wall formed into twisted mucosa covered folds=spiral valve
of Heister

204

Blood supply
The cystic artery
comes form the
right hepatic
artery which
comes off the
hepatic artery
which comes off
the common
hepatic artery
which comes off
the coeliac trunk
The cystic veins
drain into the
portal vein
205

Bile flow
206
800 ml of bile is secreted by the hepatocytes into the
biliary canaliculieach day.
The canaliculi flow into the bile ductules in the portal
triad
The bile ductules join to flow into the right and left
hepatic ducts
These join to form the common hepatic duct(above
the cystic duct)
The cystic duct from the gall bladder joins the common
hepatic duct outside the liver to form the common bile
duct
Bile flows though the ampulla of Vater when the
sphincter of Oddi relaxes and flows into the duodenum

Pancreas
207
The pancreas is a soft, tadpole-shaped gland
It extends across the posterior abdominal wall
from the duodenum, on the right, to the spleen,
on the left.
Most of the pancreas is retroperitoneal and lies
deep to the greater curvature of stomach
between duodenum and spleen

Pancreas
208
mixed gland, both exocrine and endocrine
Exocrine portion forms the bulk of the gland and secretes
enzyme rich fluid
Endocrine tissue forms islets of Langerhans scattered
throughout exocrine tissue, secrete hormone
An accessory organ, the pancreas is important to the
digestive process because it produces a broad
spectrum of enzymes
These enzymes break down all categories of foodstuffs
This exocrine product is called pancreatic juice

Pancreas
209
Parts
Head
Expanded part
Embraced by C-shaped curve of duodenum
Uncinate process projection from inferior part
Neck
Overlies superior mesenteric vessels
Body
Main part
Tail
Related to hilum of spleen
Structure
Highly lobulated
Invested by thin collagenous capsule which sends septa
between lobules

210

Exocrine pancreas
Pancreatic acini
made up of irregular
clusters of pyramidal
secretory cells, the
apices of which surround
a central lumen
Cells are typical protein
secreting cells
Aciniare surrounded by
basement membrane
supported by reticular
fibers
Between acini are CT
with capillaries
211

Endocrine pancreas
212The pancreas also has an endocrine function
Isolated clumps of endocrine cells scattered in
exocrine tissue = islets of Langerhans
Vary in size and numerous in tail
Composed of clumps of secretory cells + fine
collagenous network + fenestrated capillaries
Delicate capsule surround islets
Cells
2 main types
1.Glucagon secreting cells
Distributed towards periphery
2.Insulin secreting cells

213
Duct system
Lumen of acinus drain into intercalated ducts
Initial portion penetrate the lumen, duct cells
=centroacinar cells
Intercalated ducts drain into intralobular ducts
Intralobular ducts drain into interlobular ducts
Pancreatic juice drains from the pancreas via the
centrally located main pancreatic duct
The pancreatic duct generally fuses with the bile
duct just as it enters the duodenum
A smaller accessory pancreatic duct empties
directly into the main duct

Blood supply and innervation
214
Vessels
Pancreatic arteriesfrom splenic artery
Pancreaticoduodenal arteriesfrom superior
mesenteric artery
Pancreatic veinsdrain to splenic and superior
mesenteric veins
Nerves
From vagus and splanchnic nerves

Large Intestine
215
The large intestine frames the small intestine on three
sides and extends from the ileocecal valve to the anus
Its diameter is greater than that of the small intestine,
but is less than half as long 1.5 meters
Its major function is to absorb water fromindigestible
food residues (delivered to it in fluid state) and eliminate
them from the body as semisolid feces
Two main functions:
1.Storage of stool
2.Reabsorption of water and electrolytes to turn semi liquid small
intestinal contents into formed faeces

The position of the colon in the abdomen
216

217

Large Intestine
218
Over most of its length, the large
intestine exhibits three features
teniae coli
Haustra
epiploic appendages

Large Intestine
219
Teniae coli
three bands (narrow strap) of smooth muscle that run the length of
the large intestine
the remnants of the smooth muscle layer
Because the taenia (= ribbon or tape)are shorter than the intestine
the colon becomes sacculated between the taenia forming “haustra”
(latin = drawer)
In between haustra are folds known as the plicae semilunares
The taenia fuse at the appendix. The surgeon may find this useful in
locating the appendix
Haustra
pocket like sacs formed when the tonic contraction of the teniae coli
Epiplocic appendages
small fat-filled pouches of visceral peritoneum that hang from its
surface
Significance is not known

Large Intestine: subdivisions
Caecum with appendix
Colon
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
220

Large Intestine: caecum
221
The saclike cecum, or blind pouch, lies below
the ileocecal valve is the first part of the large
intestine
It is inferior to the ileocecal opening and in the right iliac
fossa
It is an intraperitoneal structurebecause of its mobility
not because of its suspension by a mesentery
The cecum is continuous with the ascending colon at the
entrance of the ileum and is usually in contact with the
anterior abdominal wall
The appendix is attached to the posteromedial wallof the
cecum, just inferior to the end of the ileum

Large Intestine: appendix
222
The appendixis a narrow, hollow tube connected
to the cecum
It has large aggregations of lymphoid tissuein
its walls
Suspended from the terminal ileum by the
mesoappendix,which contains the
appendicular vessels
It has a significant structural problem in that its
twisted tissue provides an ideal location for
enteric bacteria to accumulate and multiply

McBurney’s point
The appendix is
normally situated at
McBurney’s point
1/3 of the way along a
line from the anterior
superior iliac spine to
the umbilicus
223

Large Intestine: appendix
224
Its point of attachment to the cecumis consistent
with the highly visible free taenialeading
directly to the base of the appendix
The location of the rest of the appendix varies
considerable. It may be:
posterior to the cecumor the lower ascending colon,
or both, in a retrocecalor retrocolicposition
suspended over the pelvic brim in a pelvic or
descending position
below the cecumin a subcecallocation
anterior to the terminal ileum, possibly contacting the
body wall, in a preilealpositionor posterior to the
terminal ileum in a postilealposition

Large Intestine: appendix
225
General structure is similar to the rest of large
intestine
Particularly in young there are masses of
lymphoid tissue in mucosa and submucosa
Glands are fewer and shorter
Has no teniae coli
Because it is blind-ended, its contents are not
renewed rapidly thus it becomes a frequent site
of inflammation = appendicitis

226

Large Intestine: colon
227
The colon extends superiorly from the cecum
and consists of the ascending, transverse,
descending, and sigmoid colon
Its ascending and descending segments are
retroperitoneal and its transverse and
sigmoidsegments are intraperitoneal
The ascending colon travels up the right side
of the abdominal cavity to the level of the right
kidney

Large Intestine: colon
228
At the junction of the ascending and transverse
colon is the right colic flexure, which is just
inferior to the right lobe of the liver
The transverse colon travels across the top of
the abdominal cavity
A similar, but more acute bend (the left colic
flexure)occurs at the junction of the transverse
and descending colon
This bend is just inferior to the spleen, higher
and more posterior than the right colic flexure,
and is attached to the diaphragm by the
phrenicocolic ligament

Large Intestine: colon
229
The descending colon descends down the left
side of the abdominal cavity
As the descending colon enters the pelvis it
forms the S-shaped sigmoid colon
The sigmoid colon begins above the pelvic inlet
and extends to the level of vertebra S3,where
it is continuous with the rectum
This S-shaped structure is quite mobileexcept at
its beginning where it continues from the
descending colon, and at its end, where it
continues as the rectum. Between these points,
it is suspended by the sigmoid mesocolon

Large Intestine: colon
230
The transverse and sigmoid portions of
the colon are anchored to the posterior
abdominal wall by mesentery sheets
called mesocolons
In the pelvis, at the level of the third
sacral vertebra, the sigmoid colon joins
the rectum, which is positioned anterior
to the sacrum

Large Intestine: rectum
231
Extending from the sigmoid colon is the rectum
Internally are transverse folds called rectal
valves
Rectal valves separate feces from
flatus, thus allowing gas to pass

Large Intestine: anal canal
232
The continuation of the large intestine inferior to
the rectum
Lies entirely external to the
abdominopelvic cavity
About 3 cm longthe canal begins
where the rectum penetrates the
muscles of the pelvic floor

Large Intestine: anal canal
233
The anal canal has two sphincters
External anal sphincter
Internal anal sphincter
The involuntary internal anal sphincter is
composed of smooth muscle
The voluntary external anal sphincter is
composed of voluntary muscle
These sphincters which act to open and close
the anus, are ordinarily closed excepts during
defecation

Large Intestine: Microscopic anatomy
234
Ileo-caecal junction
Abrupt transition in lining of ileo-caecal valve from villiform pattern
in small intestine to glandular form in large intestine
Mucosa
Cells types
Absorptive cells
Mucus secreting goblet cells
Mucosa arranged in closely packed tubular glands
Folded in non distended state but no plicae circularis
Above anal valve mucosa forms longitudinal folds= anal
columns (column of Morgagni)
The anal sinusesare recesses between the anal columns which
exude mucus when compressed by feces
This aids in the emptying of the canal

235

236
Glands
Extends to muscularis mucosae
Separated by thin lamina propria
Muscularis mucosae extend into lamina propria,
contraction facilitate mucus expulsion
Goblet cells dominate in base,luminal surface lined
by columnar absorptive cells
Above anal opening mucosa is transformed
to stratified squamous
Lamina propria contains plexus of veins which dilate
and varicose producing hemorrhoids

237
Lamina propria
Contain numerous blood and lymphatic vessels and
lymphoid aggregations that extend to submucosa
Muscularis mucosae
Prominent, contraction prevent clogging of glandsand
enhance expulsion of mucus
Muscularis
Thick
Inner circular and outer longitudinal
Longitudinal layer forms 3 separate bands=taeniae
coli
Serosa
In intraperitoneal portion characterized by small
pendulous protuberances filled with adipose
tissue=appendices epiploicae

238
Recto-anal junction
Rectal mucosa at this junction
undergoes an abrupt transition to
stratified squamous epithelium in anal
canal reflect greater abrasions
Muscularis layers are larger for its’
expulsive role
At anal sphincter the stratified squamous
epithelium undergoes a gradual
transition to skin

Large Intestine: Microscopic anatomy
239
The wall of the large intestine differs in several
ways from that of the small intestine
The colon mucosa is simple columnar epithelium
except in the anal canal
Because most food is absorbed before reaching the
large intestine, there are no circular folds, no villi,
and no cells that secrete digestive enzymes
Thicker mucosa, deeper crypts, very high numbers of
goblet cells
Lubricating mucus produced by goblet cells eases the passage
of feces and protects the intestinal wall from irritating acids and
gases released by resident bacteria in the colon

Large Intestine: Microscopic anatomy
240
In contrast to the more proximal regions of the
large intestine, teniae coli and haustra are
absent in the rectum and anal canal
Consistent with its need to generate strong
contractions to perform its expulsive role, the
rectum’s muscularis muscle layers are
complete and well developed

Blood Supply of the gut
241
The splanchnic circulation
includes arteries branch off the abdominal aorta to
serve the digestive organs and the hepatic portal
circulation
The hepatic, splenic and left gastric branches of
the celiac trunk serve the spleen, liver, and
stomach
The mesenteric arteries(superior and inferior)
serve the small and large intestine

Blood Supply of the gut
242
The arterial supply to the abdominal organs is
approximately one quarterof the cardiac output
The hepatic portal circulationcollects nutrient-
rich venous blood draining from the digestive
viscera and delivers it to the liver
The liver collects the absorbed nutrients for
metabolic processing or for storage before
releasing them back to the bloodstream for
general cellular use

Arterial supply
243
The abdominal aorta has anterior, lateral, and
posterior branchesas it passes through the
abdominal cavity
The three anteriorbranches supply the
gastrointestinal viscera:
celiac trunk
superior mesenteric
inferior mesenteric arteries

244

Celiac trunk
245
supplies the foregut including liver,stomach,
duodenumand spleen
divides into
Splenic artery
Hepatic artery
Left gastric artery

246

247

Superior mesenteric artery
248
Supplies the mid gutfrom the duodenal
papilla, including the distal duodenum, the
jejunum,ileum,caecum,ascendingand
transverse colonto the splenic flexure

249

250

Inferior mesenteric artery
251
Supplies splenic flexure, descending,
sigmoid colon
Meets the middle and inferior rectal arteries
which arise from the iliac vesselsat the
internal anal sphincter
There are anastomosesbetween the superior
and inferior mesenteric arteries

252

253

Venous drainage
254
Blood from the intestine is nutrient rich
It all drains into the portal veinwhich flows into
the hilum of the liver
The portal vein then branches eventually
forming the liver sinusoidsthat perfuse each
liver cell
After processing by the liver cells, the blood is
collected again in the hepatic veinswhich flow
into the inferior vena cava and on to the right
atrium

All venous blood from the abdomen drains into the
portal vein and into the liver
255
The Inferior mesentericvein drains into the
Splenic veinwhich joins the Superior
mesenteric veinto form the Portal vein

The portal venous system
256
The portal vein drains venous blood from the
gastrointestinal tract,spleen,pancreas,and
gallbladder to the sinusoids of the liver; from
here, the blood is conveyed to the systemic
venous system by the hepatic veins that drain
directly into the inferior vena cava
The portal vein is formed by the union of the
splenic veinand the superior mesentericvein
posterior to the neck of the pancreas at the level
of vertebra LI
the inferior mesenteric vein joining at or near the
angle of union

The portal veins
257
On approaching the liver, the portal vein divides
into rightand left branches, which enter the
liver.
Other tributaries to the portal vein include:
rightand left gastric veinsdraining the lesser
curvature of the stomach and abdominal esophagus
cystic veinsfrom the gallbladder
para-umbilical veins,which are associated with the
obliterated umbilical vein and connect to veins on the
anterior abdominal wall

258

259

260

261

Comparison of arterial and venous
supply of the g-i tract
262
Venous Arterial

Portacaval system (portosystemic anastomosis)
263
Connections between portal and systemic venous systems
The sites of anastomosis are:
gastroesophageal junction
Between esophageal veins draining into the azygos vein (systemic) or left
gastric vein (portal). When dilated, these are esophageal varicos
anus
Between rectal veins, the inferior and middle draining into the inferior vena
cava (systemic) and the superior continuing as the inferior mesenteric
vein (portal). When dilated, these are hemorrhoids
anterior abdominal wall around the umbilicus
Paraumbilical veins (portal) anastomosing with small epigastric veins of
the anterior abdominal wall (systemic). These may produce the "caput
medusae"
Twigs of colic veins (portal) anastomosing with systemic
retroperitoneal veins

264

Portal hypertension
If portal vein pressure is very high (e.g. in
cirrhosis), the portal blood cannot all get through
the liver
Back pressure in the portal vein opens up small
pre-existing connectionsbetween the portal
venous system and the systemic/caval venous
system
Blood then bypasses the liver through these
connections
Anastomotic veins become engorged,dilated, or
varicose;as a consequence, these veins may
rupture
265

INNERVATION OF THE
INTESTINE
266

Autonomic nervous
system
controls the
musclesthat move
and grind food in
the intestine
controls blood flow
to the intestine
Stimulates or inhibits
digestion
Feeds into the
intrinsic enteric
nervous system
267
Parasympathetic:
normal everyday
function
Sympatheticfight
or flight

Autonomic nervous system
268
sympatheticnerve fibres from the spinal cord link to the para-
vertebral sympathetic chainthen to three sympathetic ganglia before
finally linking to the intestine:
•coeliac
•superior mesenteric
•inferior mesenteric
Parasympathetic nerves via the vagusand the pelvic splanchnic
nervespass straight to the target organ
The autonomic nervous system transmitsto the gut and other
organs via efferent nerves
It also receives information from those organs and transmits that
information to the spinal cord and brain via afferent nerves
The autonomic nervous system links to the enteric nervous system

269

The enteric nervous system
270The gut’s brainwith its own distinct habits and rhythms
It influences motor, endocrine and secretory functionof the gut as
well as blood vessel tone
It receives impulses from the extrinsic autonomic nervous system
and gives information back to the autonomic nervous system on the
degree of stretch and the contents of the intestine
The intrinsic enteric nervous system is connected to
chemoreceptors, osmoreceptorsand mechanical receptorsin the
mucosa
The stomach “knows” when you have had a fatty meal and if you have
had a fatty meal it delays emptying the meal.
Fat from you meal when it reaches the ileum will delay gastric emptying:
“the ileal brake”.
You know when you feel full after a meal. You know when you are
constipated.
The enteric nervous system has been called the little brain

The intrinsic enteric nervous system is focussed in
two layers
1.Submucosal
plexus
immediately
below the inner
circular muscle
layer
2.Outer
myenteric
plexusbetween
the two muscle
layers
271

Summary
272
•Parasympathetic (generally stimulates) via
the vagus (oesophagus to proximal colon) or
via pelvic nerves (distal large intestine)
•Sympathetic (generally inhibits)T8-L2.
Enteric Nervous System
Smooth
muscle
Endocrine
cells
Secretory
cells
Blood
vessels
Myenteric
plexus
Submucosal
plexus

THE GUT LYMPHATICS
273

The abdominal lymphatics
274
Lymphatic drainage of the gastrointestinal tract
is through vessels and nodes that end in pre-
aortic lymph nodesat the origins of the three
branches of the abdominal aorta
Coeliac
superior mesenteric
inferior mesentericgroups of pre-aortic lymph nodes
Lymph passes from these nodes up the left
thoracic duct or the right lymphatic duct which
empty into the junction of the subclavian and
jugular veins

275

The abdominal lymphatics
276
Lymph from the abdominal nodesdrains into
the cisterna chyli,a sac at the inferior end of
the thoracic duct.
The thoracic ductreceives all lymph that forms
inferior to the diaphragm and empties into the
junction of the left subclavian and left internal
jugular veins

277
Stomach and small intestine

278
Spleen and pancreas

279
Large intestine

280
Liver and kidney

Spleen
281
The spleen develops as part of the vascular system in
the part of the dorsal mesentery that suspends the
developing stomach from the body wall
In the adult, the spleen lies against the diaphragm, in the
area of rib IX to rib X
It is therefore in the left upper quadrant, or left
hypochondrium,ofthe abdomen
Function
Production of immunological response
Removal of particulate matter and aged erythrocytes
Analogous to lymph node, lymph is replaced by blood

Spleen
282
The spleen is connected:
to the greater curvature of the stomach by the gastrosplenic
ligament,which contains the short gastric and gastro-omental
vessels
to the left kidney by the splenorenal ligament,which contains
the splenic vessels
Both these ligaments are parts of the greater omentum
The spleen is surrounded by visceral peritoneum except
in the area of the hilum on the medial surface of the
spleen
The splenic hilumisthe entry point for the splenic
vessels and occasionally the tail of the pancreas reaches
this area

283

Structure
284
Supporting tissue
Enclosed by dense fibro-elastic capsulewhich
send septa
Capsule continue to ensheath blood vessels
Network of reticular tissue forms skeleton
Parenchyma
Macroscopically white spots (white pulp)
embedded in a red matrix (red pulp)

THE URINARY SYSTEM
285

Functions of the Urinary System
286
Filtration of the blood
Occurs in the glomerulus of the kidney nephron
Contributes to homeostasis by removing toxins or waste
Reabsorption of vital nutrients, ions and water
Occurs in most parts of the kidney nephron
Contributes to homeostasis by conserving important materials
Secretion of excess materials
Assists filtration in removing material from the blood
Contributes to homeostasis by preventing a build-up of certain
materials in the body such as drugs, waste, etc.
Activation of Vitamin D
Vitamin D made in the skin is converted to Vitamin D3 by the kidney
Active Vitamin D (D3) assists homeostasis by increasing calcium
absorption from the digestive tract

Functions of the Urinary System
287
Release of Erythropoietin by the kidney
Erythropoietin stimulates new RBC production
Release of Renin by the kidney
Renin stimulates the formation of a powerful
vasoconstrictor called Angiotensin II
Release of Prostaglandins
Prostaglandins dilate kidneyblood vessels
Dilated blood vessels contribute to homeostasis by
maintaining blood flow in the kidneys
Secretion of H
+
and reabsorption of HCO3
_
Eliminates excess hydrogen ions and conserves buffer
material such as bicarbonate
Contributes to homeostasis by controlling acid/base
conditions in body fluids

Organs of Urinary System
Kidneys
Urinary bladder
Ureters
Urethra
288

Kidney
Location
Each kidney lies in
paravertebral grooves
on posterior abdominal
wall retroperitoneally
The kidneys extend
from the level of the
T12 to L3
They receive some
protection from ribs
289

Kidney: Location
The right lies
somewhat lower
than left as it is
positioned under
liver
290

Relations
291
posterior:
Muscles: diaphragm, psoas major, quadratus lumborum
and the origin of the transversus abdominisfrom medial
to lateral
Nerves: subcostal, iliohypogastric and ilioinguinal nerves
Anterior:
Right kidney
Superior pole: liver, suprarenal
Hilum: duodenum
Inferior pole: part of small intestine, right colic flexure
Left kidney
Suprarenal gland, stomach, spleen, pancreas, jejunum,
descending colon

External Anatomy
292
The adult kidney weighs about 150 g
Size: 12 cm long, 6 cm wide, 3 cm thick
Color: reddish-brown
Shape: bean-shaped
The lateral surface of each kidney is convex,
while the medial is concave

293

External Anatomy
Medial surface has a
vertical cleft called
the renalhilusthat
leads into the space
within the kidney
called the renal sinus
Atop each kidney is
an adrenal gland
294

External Anatomy
Ureters, renal blood
vessels, lymphatics,
and nerves enter
the kidney at the
hilus
These structures
occupy the renal
sinus
295

Position
The kidneys are retroperitoneal,or behind the
peritoneum
296

Supportive tissue
Kidneys are supported by three layers of supportive tissue
The renal capsule
The outer membrane that encloses, supports and protects the
kidney
adheres directly to the kidney surface and isolates it from
surrounding region
The adipose capsule
attaches the kidney to the posterior body wall and cushions it
against trauma
The renal fascia
dense fibrous connective tissue which surrounds the kidney and
anchors these organs to the surrounding structures
297

Internal Anatomy
298
The kidney has three distinct regions
Cortex
Medulla
Pelvis

299

Internal Anatomy: Cortex
300
The outer layer of the kidney
Light in color and has a granular appearance
Contains most of the nephron; main site for
filtration, reabsorption and secretion

Internal Anatomy: renal medulla
301
Deep to the cortex; inner core of the kidney
Darker tissue which exhibits cone shaped tissue
masses called medullary or renal pyramids
Contains the pyramids,columns, papillae, and
parts of the nephron
Used for salt, waterand urea absorption

Internal Anatomy: renal medulla
302
Renal pyramid
Triangular units in the medulla that house the loops
of Henle and collecting ducts of the nephron
Each renal pyramid has a base which is convex, and
an apex which tapers toward its papilla
Renal Papilla
The tip of the renal pyramid that releases urine into a
calyx

303

Internal Anatomy: renal medulla
304
The apex, or papilla, points internally
The pyramids appear stripedbecause they are
formed almost entirely of roughly parallel
bundles of urine collecting tubules

Internal Anatomy: renal medulla
305
Inward extensions of cortical tissue called
renal columnsseparate the pyramids
Each medullary pyramid is surrounded by a
capsule of cortical tissue to form a lobe

Internal Anatomy: renal pelvis
306
Within the renal sinus is the renal pelvis
This flat, funnel shaped tube is continuous with
the ureter leaving the hilus
Branching extensions of the renal pelvis form 2-
3 major calyces,each of which sub-divides to
form several minor calyces
Calyx
A collecting sac surrounding the renal papilla
transports urine from the papilla to the renal
pelvis

Internal Anatomy: renal pelvis
307
Renal pelvis collects urine from all of the
calyces
Urine flows through the renal pelvis into the
ureter, which transports it to the bladder
The walls of thecalyces, pelvis,and ureter
contain smooth musclewhich contract to move
urine

308

Blood Supply
309
Kidneys possess an extensive blood supply
Under normal resting conditions, the renal arteries deliver
approximately one-fourth of the total systemic cardiac
output (1200 ml) to the kidneys each minute
The renal arteries issue at right angles from the abdominal
aorta
Each renal artery divides into segmental arteriesthat enter
the hilus
The segmental arteries branches into lobarand then
interlobar arteries,which pass through the renal columns
toward the cortex

310
Interlobar arteries then form arcuate arteries
Arcuate arteries branch into the cortex and
lead to interlobular arterieswhich distribute the
blood evenly throughout the cortex to the
afferent arterioleswhich serve the nephrons
Blood flow leaving the nephrons returns by
veins of the corresponding names

311
Figure 26.5a, b

312

313
Figure 26.5c, d

Uriniferous tubule
314
The main structural and functional unit of the
kidneys is the uriniferous tubule
The unit consists of a nephron and its
collecting duct or tubule
Uriniferous tubules are separated from one
another by small amounts of loose areolar
connective tissue called interstitial connective
tissue

315
Uriniferous tubule

Uriniferous tubule
316
Throughout its length the uriniferous tubule is
lined by a simple epitheliumthat is adapted for
various aspects of the production of urine

Nephrons
317
Each kidney contains over 1 milliontiny blood
processing units called nephrons,which carry
out the processes that form urine
Nephrons are the physiological unit of the
kidney used for
filtration of blood and reabsorption and secretion
of materials

Nephrons
318
The nephron is composed of
Renal corpuscle
Renal tubule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule

319

Nephron
Each nephron
consists of a
glomerulus,a tuft of
capillaries
associated with a
renal tubule
The end of the renal
tubule is a blind,
enlarged, and cup-
shaped and
completely surround
the glomerulus
320
Glomerulus

Nephrons -Renal Corpuscle
The renal corpuscle comprises the enclosed
glomerulus and the capsule of the glomerulus called
Bowman’s capsule
321

Nephrons -Renal Corpuscle
322
The first part of the nephron, where the
filtration occur
Spherical
Consist of a tuft of capillariescalled a
glomerulussurrounded by a cup shaped,
hollow glomerular capsule (Bowman’s
capsule)

A Renal Corpuscle

Nephron -Renal Corpuscle
Each nephron is
served with blood by
the afferent arteriole
This vessel brings
blood into a capillary
tuft called the
glomerulus
Blood leaving the
glomerulus flows into
the efferent arteriole
324

Renal Corpuscle: glomerulus
A capillary tuftdiffers from a
capillary bed in that it does not
perfuse a tissue like a capillary
bed does
Instead this capillary tuft is a
condensed mass of capillaries
which allows substances to
escape by filtration
Space between capillary loops
are filled by specialized
connective tissue called
mesangium
Consists mesangial cells and ECM
Provide support for capillary loops
phagocytic
325

Renal Corpuscle: glomerulus
326
The site for blood filtration
Operates as a nonspecific filter; in that, it will remove
both useful and non-useful material
The glomerulus lies in the glomerular capsule like an
under inflated balloon
The capillaries of this tuft are surrounded by specialized
cells which form the inner (visceral) layer of Bowman's
capsule

Renal Corpuscle: Bowman's capsule
A sac that encloses
the glomerulus
Transfers filtrate from
the glomerulus to the
Proximal Convoluted
Tubule (PCT)
327

Nephron: Bowman's capsule
328
The outer parietal layer of the glomerular
capsule is composed of simple squamous cells
with tight junctionsand serves to contain the
filtrate in the capsular space
It contributes to the structure of the capsule
It plays no part in the formation of filtrate

Nephron: Bowman's capsule
329
The glomerulus endothelium is fenestrated
(penetrated by many pores),which make these
capillaries highly porous
The capillaries allow large amounts of fluid and
small molecules to pass from the capillary blood
This plasma-derived fluid or filtrate is the raw
material that is processed by the renal tubules to
form urine

Nephron: Bowman's capsule
330
The fluid passes from the capillary into the
hollow interior of the glomerular capsule, the
capsular space
This fluid is the filtrate that is ultimately
processed into urine

Nephron: Bowman's capsule
331
The capsule’s visceral layerclings to the
glomerulus and consists of unusual, branching
epithelial cells called podocytes

Nephron: podocytes
The capillaries of the
glomerulus are surrounded by
specialized cells which form
the inner (visceral) layer of
Bowman's capsule.
These specialized cells are
called podocytes (foot cells)
because they have processes
called pedicels which
interdigitate or interlace
producing openings called
filtration slits
The capillaries are
fenestrated in order to allow a
large amount of filtration
332

Filtration membrane
Lies between the
blood and the
interior of the
glomerular
capsule
It is a porous
membrane that
allows free
passage of water
and solutes
333

Filtration membrane
The filtration membrane is a double layered membrane
composed of
the endothelial cells of the capillary wall
the podocytes of the visceral layer of Bowman’s
capsule
Substances make their way through the capillary
fenestrations, then through the combined basement
membranes of capillary and podocyte cells, and through
the filtration slits into the capsular space
It is a porous membrane that allows free passage of water
and solutes smaller that plasma proteins
The capillary pores prevent passage of blood cells, but
plasma components are allowed to pass
334

Filtration membrane
335
Consists of 3 layers
1.Capillary endothelium
Numerous fenestrae with out diaphragm
2.Glomerular BM
Thicker than other BM
Fused common BM
3.Podocytes
Long cytoplasmic processes embracing capillaries=primaryprocesses
Each primary process give short secondary processes=pedicels
Interdigitate with others
Directly applied to BM
Gaps between adjacent secondary processes=filtration slit
Bridged by diaphragm

Renal Tubules
336
Extend from Bowman’s capsule to collecting duct
Lined by single layer of epithelial cells
Function
Selective reabsorption of water and ions
Secrete ions
4 zones
Proximal convoluted tubule (PCT)
In cortex
Highly convoluted, except distal part
Surrounded by capillaries
Lined by cuboidal cells with brush border
Basal plasma membrane exhibit deep infoldings
Elongate mitochondria between folds
Lateral interdigitation between adjacent cells

Renal Tubules
337
. Loop of Henle
U shaped
Arise from PCT as thin walled
Descend to medulla as thin descending limb
Loops back as thin ascending limb
Finally become thick walled
Length varies based on location of corpuscle
Short looped and Long looped nephrons
Closely associated with capillaries = vasa recta

Renal Tubules
338
Distal convoluted tubule (DCT)
Continuation of thick limb
Short and less convoluted
Lined by simple cuboidal epithelium
Basal invaginations are present
But no brush border
Cells are smaller
Collecting tubule
Straight terminal portion
Lined by simple cuboidal
Several converge to form collecting duct
Descend in parallel bundles=medullary rays
Merge in medulla to form duct of Bellini
Open at renal papilla

Renal Tubules: summary
339
The Bowman's capsule opens into the proximal
convoluted tubule which leads to the loop of
Henle
The loop of Henle has a descending limb which
passes into the medulla, recurves, and becomes
the ascending limb which leads back up to the
distal convoluted tubule in the cortex
Distal convoluted tubules lead into collecting
tubules, which pass through the medullary
pyramids to the papillae

Nephron
Once filtered out of the plasma the urine enters
the collecting duct
Urine passes into larger ducts until it reaches
the ureters
It leaves the kidneys and moves toward the
bladder in the ureters
340

Vasculature of nephrons
341
Afferent Arteriole
Transports arterial blood to the glomerulus for filtration
Efferent Arteriole
Transports filtered blood from the glomerulus , through the peritubular
capillariesand the vasa recta,and to the kidney venous system
Efferent arteriole has smaller diameter than afferent
Maintain pressure gradient for filtration
Peritubular Capillaries
transport reabsorbed materials from the PCT and DCTinto kidney
veins
help complete the conservation process (reabsorption) that takes place
in the kidney
Usually an arteriole flows into a venule; But in this case the efferent
arteriole flows into more capillaries, the peritubular capillaries,and, in
juxtamedullary neurons, the vasa recta

342

Vasculature of the kidney: summary
343
The renal artery divides into segmental arteriessupplying
the corresponding segments of the kidneys
Segmental arteries give rise to lobar brancheswhich give
rise to interlobar branchesand arcuate arteries running
between cortex and medulla. From these arise the
interlobular arteriesradiating out to the cortex
Interlobular arteries give rise to afferent arteriolesand
efferent arterioleswith peritubular capillaries
Each nephron receives one afferent arteriole, which divide
into glomerular capillaries, which then reunite to form an
efferent arteriole
Efferent arteriole divide to form peritubular capillaries
which reunite to form Interlobular veins
Then blood drains through arcuate veins to Interlobar
veins
Blood leave kidney through Renal vein

Nephron types
Cortical nephrons
Most human nephrons are
cortical nephrons
their corpuscles are located in
the mid to outer cortex and
their loops of Henle are very
short and pass only into the
outer medulla
Juxtamedullary nephrons
their loops travel deep into the
inner medulla
These nephrons are important
in concentrating the urine by
increasing the amount of
water reabsorbed
344

Histology of nephrons
345
Proximal tubule cells
have abundant mitochondria and brush border (microvilli)for
extensive reabsorption and secretion
Distal tubule cells
are less active and are therefore thinner
Loop cells
Thin segment cells in descending limb are modified simple
squamous epitheliumfor reabsorption of water by osmosis
Thick segment ascending limb and DCT cells are similar to PCT
but have fewer microvilli and mitochondria-they also allow
secretion and reabsorption but not as much as in PCT
Collecting duct cells
cuboidal and allow minor amounts of secretion and absorption

346

The juxtaglomerular apparatus (JGA)
347
A place where the distal convoluted tubule lies close to the glomerulus
and to the afferent and efferent arterioles
Specialization of afferent arteriole and DCT
Involved in regulation of BP
It consists of 3 components
1.Macula densa
Area of closely packed, specialized cells lining DCT where it abuts to vascular
pole
Sensitive to concentrations of sodium ion
2.Juxtaglomerular cells
Specialized smooth muscle cells of afferent arteriole
Secrete enzyme renin
3.Extraglomerular mesangeal cells
Form conical mass
Function unknown

348
Functions of the JGA
Macula densa cells sense the glomerular filtration
rate via the salt (Na+)concentration in the distal
tubule
Juxtaglomerular cells secrete renininto the blood
of the arterioles

349

Lymphatic drainage and Innervation of kidneys
350
Lymph vessels follow renal veins and drain
into lumbar lymph nodes
Nerve supply is from renal plexus(lesser and
lower splanchnic nerves)

Ureters
351
Thick walled muscular duct with narrow lumina
Carry urine from kidneys to urinary bladder
It measures 25cm (10 in.)

352

Ureters
Each leaves the renal pelvis, descends behind the peritoneumto the base of the
bladder, turns and then runs obliquely through the medial bladder wall
Abdominal part
runs down anterior to the psoas major, retroperitoneally
Right ureter lies closely related to inferior vena cava, lumbar lymph nodes and
sympathetic trunk
Inferiorly, testicular or ovarian vessels cross over the ureter
Crosses pelvic brim and external iliac artery just beyond bifurcation of
common iliac arteries
Pelvic part
Course posteroinferiorly on lateral wall of pelvis anterior to internal iliac
arteries
At base of urinary bladder curve medially superior to levator ani
In the male ductus deferens lies between ureter and peritoneum
In the female uterine artery crosses superiorly lateral portion of fornix of vagina
Enters posterosuperior angle of bladder, passes obliquely through bladder
wall, opening has no anatomical valve
353

Ureters
354
Histologically, the walls of the ureter is
trilayered
An inner layer of transitional epitheliumlines the
inner mucosa
The middle muscularis layeris composed of an
inner longitudinal layer and an outer circular layer
The outer layer is composed of fibrous connective
tissue

Ureters
355
The ureters are protected from a backflow of
urine because any increase within the bladder
compresses and closes the ends of the ureters
The ureters play an active role in transporting
urine
Distension of the ureters by incoming urine
stimulates the muscularis layer to contract,
which propels the urine into the bladder
The strength and frequency of peristaltic waves
are adjusted to the rate of urine formation

Obstruction of ureter
356
Obstruction results from ureteric calculus (kidney
stones)
Ureters dilate if obstructed
Excessive distension causes severe pain –ureteric
colic,results from hyperperistalsis in ureter
Causes complete or intermittent obstruction of
urinary flow
Occur any where along ureter, but often in the 3
narrow regions
at the junction with the pelvis of the kidney
where it crosses the brim of the pelvic bone
as it enters the bladder

357
Arterial supply: It is well supplied by the renal
artery, aorta, gonadal arteries and various
pelvic vessels.
Venous drainage: Testicular and ovarian veins
Lymphatic drainage: aortic, common iliac,
external iliac and internal iliac lymph nodes
Innervation: renal , testicular/ovarian, inferior
hypogastric plexus

Suprarenal glands
358
Pair of ductless glands on the upper poles of each kidneys
Right suprarenal
Triangular, partly covered with peritoneum
Relations
•Posteriorly–diaphragm
•Postero-inferiorly–right kidney
•Anteriorly–liver and inferior vena cava
•Medial border-celiac ganglion
Left suprarenal
Semilunar, partly covered with peritoneum of the lesser sac
Relations
•Posteriorly–diaphragm
•Anteriorly–stomach ( forms stomach bed) separated by lesser
sac
•Postero-inferiorly-left kidney
•Medial border-celiac ganglion

359
Neurovasculature
Arterial supply
Superior suprarenal arteries -from phrenic artery
Middle suprarenal arteries-from abdominal aorta
Inferior suprarenal arteries-from renal artery
Veins –single vein from each
Left –drains into left renal vein
Right-directly into IVC
Nerve supply
Sympathetic preganglionic from splanchnic nerves,
reach through celiac & renal plexuses

General structures
360
Thick CT capsule
bringing arteries to serve radial capillaries draining down towards the
venules and central vein of the medulla
Arterioles also penetrate the cortex to serve a medullary capillary bed
Cortex
Polyhedral glandular cells, in cords usually two cells wide, run
roughly radially, along with sinusoidal capillaries
Medulla
thin strip of basophilic cells
Embryologically and functionally distinct
Mesodermal cells of coelomic mesotheliumdifferentiate
into cortex
Neural crestform the medulla

Adrenal Cortex
361
Cells of the adrenal cortex have the
characteristic structure of steroid synthesizing
cells
The cortex has 3 layers, the zonae
glomerulosa, fasciculata, and reticularis

Zona glomerulosa
362
Outermost cortical, beneath the capsule and
constitutes 15% of adrenal volume
cells form arched clusters (glomeruli)
surrounded by capillaries
The secretory cells produce
mineralocorticoids

Zona fasciculata
363
middle layer of the adrenal cortex, constitutes
65% of adrenal volume
cells form straight cords (fascicles)
that run perpendicular to the organ
surface
produce glucocorticoids and some
adrenal androgensupon appropriate
stimulation

Zona reticularis
364
Innermost layerof the adrenal cortex and
constitutes 7% of adrenal volume
Cells are arranged in irregular cordsthat form an
anastomotic network (reticulum)
Its cells resemble those in the fasciculata but are
smaller and more acidophilic
They contain fewer lipid droplets, more
mitochondria, and numerous lipofuscin granules

Adrenal Medulla
365
It contains 2 major cell types:
Chromaffin cells
ganglion cells
Ganglion cells
few parasympathetic ganglion cells
Chromaffin cells
the predominant medullary cell type
modified postganglionic sympathetic neurons that
have lost their axons and dendrites
Synthesize and release their catecholamines upon
neural stimulation,especially stress, mediated by
preganglionic sympathetic neurons

366

367
The posterior abdominal wall

Introduction
368
The posterior abdominal wall consists
Bones
lumbar vertebrae
sacrum
ilium
Muscles
Psoas
quadratus lumborum
transversus abdominis muscle
posterior part of the diaphragm and its crura
The parietal peritoneum covers the posterior abdominal
wall along with the retroperitoneal organs
duodenum and the kidneyslying on the vertebrae and muscles

369

Bones
370

Muscles
371
Psoas major
arises from the transverse processes and sides of the
bodies and intervertebral discs of the 5 lumbar
vertebrae
passes with iliacus (Iliacus arises from the inner surface
of ilium) under the inguinal ligament
insert in to the lesser trochanterfusing with iliacus
(iliopsoas)
innervated by L1, 2 and 3 insidethe abdomen
flexes the hip joint
Because the muscle fills in the angle between the
transverse processes and the sides of the bodies of the
vertebrae, it covers the intervertebral foramina
The lumbar plexus thus enters the psoas major and its
branches emerge from the surface of the muscle

372

Iliacus
O -iliac fossa
I -lesser
trochanter of
femur
A -hip flexion
373

374

Iliopsoas
375
Iliacus and psoas muscle
Covered by dense layer of fascia so that
muscles and lumbar plexus are behind fascia
and iliac vessels are in front of it

Psoas
minor
An occasional small
muscle belly with its
long tendon lying over
the psoas major
O -transverse
processes and bodies of
T12 and L1
I -rim of acetabulum
A -flexes lumbar
vertebrae
376

Quadratus lumborum
377
Lies lateral to psoas, running between the iliac
crest and R12
It is a side flexor of the trunk
Innervated segmentally by the adjacent lumbar
nerves

378

379

Abdominal aorta:Location
380
Continuation of thoracic aorta
Lies in the midline against vertebral bodies
It enters the abdomen through aortic hiatusat
T12 and L1 level
Ends at L4,left of the midline by dividing into
the 2 common iliac arteries.
The main continuation of the aorta is the
median or middle sacral artery

381

Abdominal aorta: relations
Superior: diaphragm
Anterior: celiac trunk and plexus, pancreas, left
renal vein, duodenum, mesentry
Posterior: bodies of L1-L4 vertebrae, cisterna chili
Lateral: inferior vena cava (right), left ciliac
ganglion, sympathetic trunk
382

383

Abdominal aorta: Branches
384
Subdivided into groups of 4:
3 unpaired visceral
paired visceral
paired parietal
unpaired parietal

Branches
385
Inferior phrenic: T12
Celiac trunk: T12/L1
SMA: L1
Renal & Gonadals: L2
IMA: L3
Bifurcation:iliac L4

386

387

Unpaired visceral branches
388
Ventral branches;arise from anterior surface
arteries to the fore-, mid-and hindgut respectively
celiac trunk
superior mesenteric
inferior mesenteric
Celiac trunk:
Foregut oesophagus to D2
Superior mesenteric
MidgutD3 to distal 1/3 transverse colon
Inferior mesenteric
Hindgutdistal 1/3 transverse colon to upper 2/3 of
rectum

389

Paired visceral branches
Arise from sides; lateral branches
Supply the suprarenal glands, kidneys and the gonads
Renal arteries
Arise just below the superior mesenteric artery
The right renal artery passes posterior to the inferior vena cava
They also send branches to the suprarenal glands and the renal
pelvis
Pass to hilum of kidney between ureter and renal vein
Gonadal (ovarian or testicular) arteries
Arise from the aorta just below the renal arteries
They descend lying anterior to the surface of the psoas to reach the
ovary or pass into the inguinal canal to go to the scrotum
Middle suprarenal arteries
Arise near the origin of SMA
390

Paired parietal branches
391
Arise from posterolateral surface
Are branches to the body wall
The inferior phrenic arteries
Gives branch to the suprarenal gland and ramify on the
inferior surface of the diaphragm
The 4 lumbar arteries
gives a posterior branchgoing through the back and
giving a spinal branch
The anterior branchruns in the anterior abdominal wall
between the transversus and the internal oblique
muscle

Unpaired parietal branches
392
Arise from posterior surface
The median (middle) sacral artery
in the midline, anterior to the sacrum
from bifurcation of aorta

Inferior Vena Cava
393
Returns blood from lower limbs, abdominal wall
and abdominopelvic viscera
begins in front of the body of L5by union of
common iliac veins
ascends, on right psoas muscle right to aorta,to
the diaphragm
pierce the central tendon at T8forming vena
caval foramen
Relations
posterior: bodies of L3-L5, right psoas major muscle, right
sympathetic trunk, right renal artery, right suprarenal gland
anterior: superior mesenteric vessels, head of pancreas,
duodenum
lateral: aorta (left), right ureter and kidney (right)

Tributaries
394
Ventral tributary: right testicular or ovarian vein
Lateral tributaries: renal and right suprarenal
and hepatic veins
Correspond to the named arteries except on the left
where the suprarenal and gonadalveins open into the
left renal vein
Tributaries from the body wall: the inferior
phrenic and lumbar veins
the median sacral opens into the left common iliac vein

395

Lumbar plexus
396
Lies in the psoas major
Formed by the anterior primary rami of L1, 2, 3,
and 4
The sacral plexusis from L4, 5, S1, 2, 3 and 4
L4 is also called the nervus furcalisor lumbosacral
trunkbecause it splits itself between the lumbar
and sacral plexuses
The sacral and lumbar plexuses overlap
substantially
Since many of the fibers of the lumbar plexus
contribute to the sacral plexus via the lumbosacral
trunk, the two plexuses are often referred to as the
lumbosacral plexus

Branches
397
Its proximal branches innervate parts of the
abdominal wall and iliopsoas
Major branches of the plexus descend to
innervate the medial and anterior thigh
branches
iliohypogastric nerve
ilioinguinal
The genitofemoral nerve
The lateral cutaneous nerve of the thigh
The femoral nerve
The obturator nerve

Branches
398
Iliohypogastric nerve
Supply skin of inguinal region
Ilioinguinal
This runs between the layers of the anterior abdominal
wall
emerges from the superficial inguinal ring
supplies the skin on the medial side of the thigh and the
scrotum or labium majus
Genitofemoral nerve
emerges from the anterior surface of the psoas major
runs down deep to the psoas fascia
supplies cremaster musclevia its genital branch and a
small area under the inguinal ligament by its femoral
branch

399
Lateral cutaneous nerve of the thigh
emerges from the lateral border of the psoas
sweeps around the iliac fossaand leaves the abdomen by
passing under the inguinal ligament
Femoral nerve
large and emerges from the lateral border of psoas
may give branches to psoas and iliacus
It lies outside of the fascia covering psoas and iliacus
Obturator nerve
emerges from the medial border of the psoasnear the brim of the
pelvis
lying posterior to the common iliac vessels
It then travels anteriorly and inferiorly, anterior to obturator
internusand leaves the pelvis by passing through the superior
part of the obturator foramen

400

401

The autonomic nervous system in the abdomen
402
The paravertebral chain of ganglia
found along the anterior border of the psoas
White rami from the first 2 lumbar nerves pass to the ganglia and all
ganglia have gray fibers passing back to the lumbar nerves
Celiac ganglia and plexuses
lie around the celiac and mesenteric arteries
Plexuses are joined by the 3 splanchnic nerves, branches of the
vagus nerves(parasympathetic) and branches from the sympathetic
trunk
Postganglionic sympathetic fibers from plexuses travel with all the
major arteries, along with preganglionic parasympathetic fibers to
innervate viscera
Plexuses around the aorta continue downward and anterior
to the aortic bifurcation forms the superior hypogastric
plexus
This divides into the right and left inferior hypogastric plexusesjoined
by the parasympathetic pelvic splanchnic nerves (S2,3,4)

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