Digestive system

Digestive System

1. Digestive SystemDigestive System
Dr. Mrs. Deepa K. Ingawale
(Mandlik)
Dept. of Pharmacology
Poona College of Pharmacy, Pune
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2. SyllabusSyllabus
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3. Digestive SystemDigestive System
Digestion:
The breaking down of complex food material into simple food
material with the help of chemicals.
Gastroenterology:
The branch of science that deals with structure, function,
diagnosis & treatment of diseases of stomach & intestine.
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4. Digestive systemDigestive system
Two groups of organs:
Gastrointestinal (GI) tract
Accessory digestive organs
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5. Organs of digestive systemOrgans of digestive system
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6. Digestive systemDigestive system
GI tract includes;
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
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7. Digestive systemDigestive system
Accessory digestive organs includes:
Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
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8. Ingestion
•Taking food through the mouth
Movement
•Movement of food along the GIT
Digestion (Mechanical & Chemical)
•Breakdown of food by chemical &
mechanical processes
Absorption
•Transport of digested material into
cardiovascular and lymphatic system for
distribution to cells
Defecation
•Elimination of indigestible substances
from body in the form of feces
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The Digestive ProcessThe Digestive Process

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Histology of alimentary tractHistology of alimentary tract
Four layers from esophagus to anus
1.Mucosa
2.Submucosa
3.Muscularis
4.Serosa

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Histology of alimentary tractHistology of alimentary tract
Inner layer (Mucosa):
It is inner lining of GI tract.
Three sub-layers
1.Epithelium
2.Lamina propria
3.Muscularis mucosae

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Histology of alimentary tractHistology of alimentary tract
Sub-mucosa:
Present above the mucosa
Consist of areolar connective tissue.
Muscularis:
It is present above the sub-mucosa layer.
Serosa:
Outer layer of GI tract.
Made up of Simple squamous epithelium

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Oral cavity or buccal
cavity
•Lining: thick stratified
squamous epithelium
It is formed by the
Cheeks
Hard palate
Soft palates
Tongue
Mouth

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Cheeks: Forms the lateral walls of oral cavity.
The anterior portions of cheeks end at the lips.
Lips or labia: Fleshy folds surrounding the opening of mouth.
Palate: It is a septum that separates the oral cavity from the
nasal cavity, forming the roof of mouth.
Hard palate: The anterior portion of roof of mouth
Soft palate: The posterior portion of roof of mouth

14. TongueTongue
Tongue together with other
muscles forms the floor of oral
cavity.
It is made up of skeletal muscles
covered with mucous
membrane.
The upper surface and sides of
tongue are covered with
papillae, contains taste buds.
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15. TongueTongue
There are 3 varieties of papillae;
Circumvallate papillae:
These 8 to 12 papillae are arranged in inverted V shape towards the base
of tongue.
All of them contains taste buds.
Largest papillae
Filiform papillae:
Whitish in color & do not contain taste buds.
Fungiform papillae:
Smallest of the three types.
Present near the tip of tongue.
Reddish dot & contains taste buds.
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TeethTeeth
Called as dentes
Present in sockets of
mandible (lower jaw bone) &
maxilla (upper jaw bone)
Parts of teeth:
The crown
The neck
The root

17. TeethTeeth
Crown: Visible portion of tooth above the gums
Root: Embedded in the gums
Dentin: Calcified connective tissue covered by enamel
Enamel is very hard made up of calcium phosphate &
carbonate.
At the center of tooth is the pulp cavity containing blood
vessels, lymph vessels & nerves
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TeethTeeth
Two sets of teeth
•Falling out:
“Baby” teeth
Start at 6 months
Fall out between 2-6 years
•Permanent:
•It consist of 32 teeth

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Classification of teeth according to Classification of teeth according to
shape & functionshape & function
Incisors: Cutting teeth used for
cutting off food
Canines: Cone shaped used for
cutting off food
Premolars & molar: Broad, flat
surface used for grinding or
chewing of food
Incisor
Canine
Premolar
Molar

20. Salivary glandsSalivary glands
It releases saliva into oral cavity.
3 pairs of salivary glands,
Parotid gland
Submandibular gland
Sublingual gland
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21. Salivary glandsSalivary glands
Parotid gland:
Present near to the ears.
They secrete their secretions into oral cavity by parotid duct.
Largest salivary gland
Submandibular gland:
It is present in the floor of mouth & beneath the tongue.
Sublingual gland:
Smallest salivary gland
Present beneath the tongue
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22. SalivaSaliva
It is a mixture of water, ions, mucus & enzymes
About 1 to 1.5 L is secreted every day
Acidic in nature (6.35 to 6.85)
Viscous & colorless in nature
Functions:
Keep mouth moist
Dissolves food
Moistens food
Starts enzymatic digestion (Amylase=sugars to starch)
Excretion (Urea, mercury, lead, many drugs)
Antibacterial & antiviral
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23. PharynxPharynx
It is a funnel-shaped tube, 13 cm long
Extends from nose to esophagus
Composed of skeletal muscle & lined by mucous
membrane
It is divided into 3 parts:
Nasopharynx
Oropharynx
Laryngopharynx
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24. PharynxPharynx
Nasopharynx: Superior portion of pharynx.
Important for respiration.
Oropharynx: Intermediate portion of pharynx.
Laryngopharynx: Inferior portion of pharynx
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25. EsophagusEsophagus
Muscular collapsible tube
25 cm long
2 cm in diameter
lies posterior to trachea
It continuous with pharynx &
connected to stomach.
Upper & lower ends are closed
by sphincter.
Upper esophageal sphincter (UES)
Lower esophageal sphincter (LES)
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Esophagus

26. EsophagusEsophagus
Upper esophageal sphincter (UES):
Regulates the movement of food from pharynx to
esophagus.
Lower esophageal sphincter (LES):
Regulates the movement of food from esophagus to
stomach.
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27. DeglutitionDeglutition
Swallowing (deglutition):
Movement of food from mouth into stomach is called as
swallowing
Facilitated by the secretion of saliva & mucus
It occurs in the mouth, pharynx, & esophagus
Complex but fast process completed within seconds
3 phases,
Buccal swallowing
Pharyngeal swallowing
Esophageal swallowing
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28. DeglutitionDeglutition
Buccal stage: The bolus is passed from oral cavity into
the oropharynx
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29. DeglutitionDeglutition
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
Pharyngeal stage: The bolus passes from pharynx into
the esophagus

30. DeglutitionDeglutition
Esophageal stage: The bolus passes from the esophagus
into the stomach
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31. StomachStomach
Enlargement of GI tract
J shaped organ
Connecting organ between
esophagus & duodenum
Divided into 4 parts
Cardia
Fundus
Body
Pylorus
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Stomach Parts Stomach Parts
Cardia: Located near the opening
Fundus: Rounded portion
Body: Large central portion
Present below the fundus
Greater curvature: Concave border
Lesser curvature: Convex border
Pylorus: Present below the body
Pyloric antrum: Connects to the body of
stomach
Pyloric canal: Connects to the
duodenum

33. FunctionsFunctions
Act as a reservoir of food
With the peristaltic movement it causes mixing of food with
gastric juice
Mucosal lining is responsible for absorption of water, alcohol
& glucose to the blood stream
Causes secretion of 1-2 liter of gastric juice every day
Gastric lipase: Lipolytic activity
Pepsin: Breakdown of proteins to peptones
Mucus from mucus cell prevents mechanical injury to
stomach
HCl: Kills bacteria in food & gives protection
It forms intrinsic factor requires for absorption of vitamin B
12
.
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34. Gastric JuiceGastric Juice
Clear colorless juice
Acidic in nature
2 liters of gastric juice secreted daily by gastric glands in the mucosa
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35. Composition of Gastric JuiceComposition of Gastric Juice
It consists of,
Water: Liquefies the swallowed food
Mineral salts:
Mucus secreted by goblet cells: Prevents mechanical injury
to stomach
Hcl secreted by parietal cells: Kills the ingested M.O.
Intrinsic factor in gastric glands: Absorption of vitamin B
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Pepsinogen enzyme secreted by chief cells
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Small intestineSmall intestine
It continues from stomach to large
intestine
Thin & long (4 m in length)
It lies in the abdominal cavity
surrounded by large intestine
Most enzymatic digestion occurs
Most enzymes secreted by
pancreas
Almost all absorption of nutrients
3-6 hour process

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Small intestine has 3 subdivisions
•Duodenum – Superior portion (25 cm long)
•Jejunum – Middle portion (1.5 m long)
•Ileum – Terminal portion (2 m long)
Small intestineSmall intestine

38. Histology of Small IntestineHistology of Small Intestine
Wall of SI is made up of four layers
Mucosa
Sub-mucosa
Muscularis
Serosa
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39. HistologyHistology
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40. MucosaMucosa
Innermost mucosa forms fingerlike projections & they
increase surface area for absorption.
Simple columnar cells
Four types of cells present
Absorptive cells with brush border of microvilli: increases SA for
absorption and secrets enzymes
Goblet cells: Secrets mucus
Enteroendocrine cells: S cells, K cells and CCK cells, secrets
secretin
Paneth cells: Phagocytic in nature & contains lysozyme enzyme
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41. Intestinal JuiceIntestinal Juice
About 1-2 liters of juice secreted every day
Clear yellow fluid, alkaline in nature (pH 7.6 to 8.0)
It consists of
Water
Mucus
Mineral salts
Consist of several digestive enzymes:
Peptidases: breaks proteins to amino acids
Amylase: breaks starch to maltose
Lactase : breaks maltose to glucose
Lipase: Breaks glycerides, fatty acids and glycerol
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42. Mechanical Digestion in SIMechanical Digestion in SI
Two types of movements of small intestine
Segmentation
Peristalsis
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43. Mechanical DigestionMechanical Digestion
Segmentation:
These are rhythmical altering contraction and relaxation of SI.
These movements mixes the chyme with the food & bring
food particles into contact with mucosa for absorption
Digestion & absorption are promoted
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44. Mechanical DigestionMechanical Digestion
Peristalsis:
Entry of food into SI stimulates stretch receptors .
Stretch receptors covey message to CNS,
PNS stimulates contraction of intestine
SNS stimulate relaxation of intestine, decrease the motility of
SI.
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45. Chemical Digestion in SIChemical Digestion in SI
Digestion of carbohydrates:
Pancreatic amylase converts all polysaccharides to
Monosaccharides
Digestion of proteins:
Enzymes like trypsin, chymotrypsin, carboxypeptidase
converts all proteins to amino acids
Digestion of fats:
The enzyme lipase converts fats to fatty acid and glycerol
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46. Large IntestineLarge Intestine
Terminal portion of the GI tract
Functions:
Completion of absorption
Production of certain vitamins
Formation of feces
Expulsion of feces from the body
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47. Large IntestineLarge Intestine
1.5 m long and 2.5 cm in diameter
Extends from ileum to anus
It forms arch around the coiled small intestine
It is divided into,
Caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anus
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48. Large IntestineLarge Intestine
Caecum:
First part of colon
Elevated portion of LI below the ileocaecal sphincter is
Caecum
Twisted coiled tube is attached called as appendix or
vermiform appendix.
Colon:
The remaining part of LI is called as colon
Divided into four parts
•Ascending colon
•Transverse colon
•Descending colon
•Sigmoid colon
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49. Large IntestineLarge Intestine
Rectum:
Dilated portion of LI
13 cm long
Starts from sigmoid colon and ends in the anus
Stores feces which consists of undigested part of food, water,
inorganic salts and bacteria, etc.
Anus:
Short passage
3.8 cm long
Starts from rectum to the exterior
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50. Function of LIFunction of LI
Absorption:
Absorption of water by osmosis, continues until the semisolid consistency
of faeces is achieved.
Mineral salts, vitamins and some drugs are also absorbed into the blood
capillaries
Microbial activity:
The large intestine is heavily colonised by bacteria which synthesize
vitamin K & folic acid i.e. E. coli, S. faecalis.
Harmless in human
Defecation Reflex:
Mass peristalsis movements push faecal material from sigmoid colon into
the rectum.
Distension of rectal wall stimulates stretch receptors which initiates
defecation reflex that empties the rectum.
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Histology – large intestineHistology – large intestine
No villi
•Fewer nutrients absorbed
“Columnar cells” =
absorptive cells
•Take in water and
electrolytes
Goblet cells for mucus
•Lubricates stool

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LiverLiver
Largest gland in the body
1.4 kg average weight
Over 500 functions
Upper part of abdominal cavity
Right and Left lobes
Right lobe is again divided into;
Caudate lobe
Quadrate lobe
Covered by peritoneum
Falciform ligament
•A fold of peritoneum

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Liver histologyLiver histology
Made up of many functional units called as liver lobules
(about one million)
•Hexagonal structure consists of special cells called as
hepatocytes (liver cells) around a central vein
•Corners of lobules have “portal triads”
(see next pic)

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Portal triad
•Portal arteriole
•Portal venule
•Bile duct
Carries bile away
Liver sinusoids
•Large capillaries
between plates of
hepatocytes
Kupffer cells
•Liver macrophages
•Phagocytic in nature,
removes dead cells,
bacteria & foreign
matter in the blood
Liver histologyLiver histology

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Functions of liverFunctions of liver
Carbohydrate metabolism
Fat metabolism
Protein metabolism
Activation of vitamin-D
Excretion of bilirubin: Excreted in bile
Stores some vitamins (A, B
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, D, E & K)
Breakdown of RBCs & phagocytosis
Detoxification of poisons & drugs
Production of heat

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GallbladderGallbladder
Small pear shaped organ
Attaches to the liver at
back side
7-10 cm long
It has 3 parts
Fundus: Expanded portion
Body: Main part
Neck: connects to cystic
duct
Functions:
Reservoir for bile
Released stored bile

57. BileBile
Secreted by liver
Stored in gall bladder
500-1000 ml of bile are secreted
Bile has pH= 8 (Alkaline)
Composition:
Water, Mineral salts, Mucus, Bile salts, Bile pigments &
cholesterol
Functions:
Bile salts emulsify fats in small intestine
Bile salts make cholesterol & fatty acid soluble.
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PancreasPancreas
Yellowish in color
Elongated leaf shaped gland lying
below the stomach
12-15 cm long & 2.5 cm thick
Three parts
Head: Expanded portion lies near the
curve of duodenum
Body: Central portion
Tail: Tapering portion
Pancrea divided into 2 parts;
Exocrine pancrea
Endocrine pancrea

59. Histology of pancreaHistology of pancrea
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Exocrine PancreaExocrine Pancrea
Small clusters of glandular
epithelium
99% are arranged in clusters
called as acini
Sac-like structure
Acinar cells make 22 kinds of
enzymes
•Stored in zymogen granules
•Grape-like arrangement

61. Endocrine pancreaEndocrine pancrea
Remaining 1% cells are arranged in clusters called as
pancreatic islets (Islets of Langerhans).
They secrete hormone insulin, glucagon are responsible for
maintaining blood sugar level.
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Endocrine pancreaEndocrine pancrea
Islets of Langerhans are the hormone secreting cells
Insulin (from beta cells)
•Lowers blood glucose (sugar)
Glucagon (from alpha cells)
•Raises blood glucose (sugar)

63. Pancreatic JuicePancreatic Juice
1.2 to 1.5 L of pancreatic juice
Clear, colorless liquid
Composition:
Water, Salts, Sodium bicarbonate, Several enzymes
Amylase: Carbohydrate digesting enzymes
Trypsin, Chymotrypsin, Elastage: Protein digesting enzymes
Lipase: Triglyceride digesting enzymes
Ribonuclease & deoxyribonuclease: Nucleic acid digesting
enzymes
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64. Function of pancreatic juiceFunction of pancreatic juice
Neutralizes acidic contents of chyme in duodenum due to
presence of sodium bicarbonate.
Pancreatic juice provides alkaline pH for enzyme action.
Pancreatic α-amylase digests Glycogen, starch & other
complex carbohydrate to disaccharides.
Enzyme nucleotides digest nucleoproteins.
Proteins are converted to amino acid by enzyme pancreatic
trypsin & elastase.
Pancreatic lipase converts fats to fatty acid & glycerol.
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65. Disorders of digestive tractDisorders of digestive tract
Dental caries/Tooth decay:
It involves a gradual demineralization (softening) of the enamel and
dentin.
If untreated micro-organism may invade the pulp causing inflammation
and infection with subsequent death of the pulp and abscess of the
alveolar bone surrounding the root apex requiring root canal therapy.
Periodontal disease:
It is a collective term for a variety of conditions characterized by
inflammation and degeneration of the gingivae, alveolar bone,
periodontal ligament and cement.
Periodontal diseases are often caused by poor oral hygiene, by local
irritants such as bacteria, impacted food cigarette smoke.
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66. Disorders of digestive tractDisorders of digestive tract
Peptic ulcer diseases (PUD):
It is a lesion of membrane that develop in areas of gastrointestinal tract
exposed to acidic gastric juice are called as peptic ulcer.
Complications of peptic ulcer is bleeding which can lead to anaemia if
enough blood is lost.
Causes:
The bacteria Helicobacter pylori
Non-steroidal anti-inflammatory drugs
Hypersecretions of HCl
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67. Disorders of digestive tractDisorders of digestive tract
Diverticular diseases:
In Diverticular disease, saclike outpouching of the wall of colon termed as
diverticula.
Development of diverticula called as diverticulosis.
Diverticula showing inflammation called as diverticulitis.
The condition may be characterised by pain either constipation or
increased frequency of defecation, nausea, vomiting and low grade fever.
Colorectal cancer:
Cancer of colon and rectum called as colorectal cancer.
Intake of alcohol and diet high in proteins and fats are associated with
increased risk of colorectal cancer.
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68. Disorders of digestive tractDisorders of digestive tract
Hepatitis:
It is an inflammation of the liver that can be caused by viruses, drugs and
chemicals including alcohol.
Types of hepatitis.
Hepatitis-A
Hepatitis-B
Hepatitis-C
Hepatitis-D
Hepatitis-E

Anorexia Nervosa:
Anorexia is chronic disorder characterized by self induced weight loss,
negative perception of body image and physiological changes that results
from nutritional depletion.
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