Chapter 13Urinary System (111111112).ppt

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1. 27-1
Urinary System

2. 27-2
General Structure and
Functions
of the Urinary System
General Concept:

Waste products accumulate in blood
are toxic

Must be removed to maintain
homeostasis

Urinary System organs

remove waste products from the blood

then from the body

Major homeostatic system

3. 27-3
General Structure and
Functions
of the Urinary System
Organs of the Urinary System:

Kidneys

Ureters
Urinary Bladder

Urethra
Primary organs: kidneys

filter waste products from the bloodstream

convert the filtrate into urine.
The Urinary Tract:
Includes:

ureters

urinary bladder

urethra
Because they transport the urine out of the body.

4. 4

5. 5

6. 6

7. 27-7
Functions of the Urinary
System
Removing waste products from the bloodstream.
Storage of urine.

the urinary bladder is an expandable, muscular sac that
can store as much as 1 liter of urine
Excretion of urine.
Blood volume regulation.

the kidneys control the volume of interstitial fluid and
blood under the direction of certain hormones
Regulation of erythrocyte production.

as the kidneys filter the blood, they are also indirectly
measuring the oxygen level in the blood
Erythropoietin (EPO): hormone produced by kidney

Released if blood oxygen levels fall

Stimulates RBC production in red bone marrow

8. 27-8
Kidneys: Gross and Sectional
Anatomy
Retroperitoneal

Anterior surface covered with peritoneum

Posterior surface against posterior
abdominal wall
Superior pole: T-12
Inferior pole: L-3
Right kidney ~ 2cm lower than left
Adrenal gland on superior pole

9. 9

10. 27-10
Kidneys: Gross and Sectional
Anatomy

Hilum: concave medial border

Renal sinus: internal space

Houses blood vessels, lymphatic vessels,
nerves

Houses renal pelvis, renal calyces

Also fat

11. 27-11
Kidneys: Gross and Sectional
Anatomy
Surrounding tissues, from deep to superficial:

Fibrous capsule (renal capsule)

Dense irregular CT

Covers outer surface

Perinephric fat (adipose capsule)

Also called perirenal fat

Completely surrounds kidney

Cushioning and insulation

Renal fascia

Dense irregular CT

Anchors kidney to posterior wall and peritoneum

Paranephric fat

Between renal fascia and peritoneum

12. 12

13. 27-13
Kidneys: Gross and Sectional
Anatomy
Sectioned on a coronal plane:

Renal Cortex

Renal arches

Renal columns

Renal Medulla

Divided into renal pyramids

8 to 15 per kidney

Base against cortex

Apex called renal papilla

14. 27-14
Kidneys: Gross and Sectional
Anatomy

Minor calyx:

Funnel shaped

Receives renal papilla

8 to 15 per kidney, one per pyramid

Major calyx

Fusion of minor calyces

2 to 3 per kidney

Major calyces merge to form renal pelvis

Renal Lobe

Pyramid plus some cortical tissue

8 to 15 per kidney

15. 15

16. 16

17. 27-17
Blood Supply to the Kidney
About 20 to 25% of cardiac output to
kidneys
Path:
Renal artery to segmental arteries to
interlobar arteries to arcuate arteries to
interlobular arteries to:
Afferent arteriole to glomerulus to
efferent arteriole to peritubular
capilaries and vasa recta

18. 18

19. 27-19
Blood Supply to the Kidney

Blood plasma is filtered across the
glomerulus into the glomerular space.

Once the blood plasma is filtered

blood leaves the glomerulus

enters an efferent arteriole.

efferent arteriole is still carrying
oxygenated blood

a gas and nutrient exchange with the kidney
tissues has not yet occurred.

20. 27-20
Blood Supply to the Kidney
The efferent arterioles branch into one of two
types of capillary networks:

peritubular capillaries

vasa recta

these capillary networks are responsible for
the actual exchange of gases and nutrients
Peritubular capillaries: primarily in cortex
Vasa recta: surround the thin tubes that
project into the medulla.

21. 27-21
Blood Supply to the Kidney

Path for veins:

Interlobar veins to arcuate veins to
interlobular veins to the renal vein

22. 22

23. 27-23
Nephrons

The functional filtration unit in the kidney.

Consists of the following:

Renal corpuscle

Glomerulus

Glomerular capsule (Bowman’s capsule)

Proximal convoluted tubule (PCT)

Nephron loop (loop of Henle)

Ascending loop of Henle

Descending loop of Henle

Distal convoluted tubule (DCT)

collectively called the renal tubule

In both kidneys: approximately 2.5 million
nephrons.

Are microscopic: measure about 5 centimeters in
length.

24. 27-24
Nephrons
Cortical Nephrons

Near peripheral edge of cortex

Short nephron loops
Have peritubular capillaries
Juxtamedullary nephrons

Near corticomedullary border
Long nephron loops

Have vasa recta

25. 25

26. 27-26
Urine Formation
Three processes
Filtration

Renal corpuscle: forms filtrate

From blood to tubule
Reabsorption

Mostly PCT

Water and salt: rest of nephron

From tubule to blood
Secretion

From blood to tubule

27. 27-27
Renal Corpuscle
Vascular pole

Afferent and efferent arterioles
Tubular pole

Connects to PCT
Two structures:

Glomerulus and glomerular capsule
Glomerulus

Capillary bed

High pressure

fenestrations

28. 27-28
Renal Corpuscle
Glomerular Capsule

Parietal layer

Simple squamous epithelium

Visceral layer

Podocytes

Pedicels

Filtration slits

Capsular space (Bowman’s capsule): location of
filtrate
Filtration membrane

Fenestrations

Filtration slits

29. 29

30. 30

31. 27-31
Proximal Convoluted Tubule

Begins at tubular pole of the renal corpuscle.

Cells: simple cuboidal epithelium

actively reabsorb from the filtrate:

almost all nutrients (glucose and amino acids)

electrolytes

plasma proteins

Osmosis: reabsorption of 60% to 65% of the
water in filtrate.

Have microvilli

Solutes and water:

moved into blood plasma

via the peritubular capillaries.

32. 27-32
Nephron Loop (loop of
Henle)

originates at end of proximal convoluted tubule

projects toward and/or into the medulla.

Each loop has two limbs.

descending limb:

from cortex toward and/or into the medulla

ascending limb:

returns back to the renal cortex

33. 33

34. 34

35. 27-35
Distal Convoluted Tubule

begins at the end of the thick ascending limb of the
nephron loop

adjacent to the afferent arteriole (important physiologically)

Juxtaglomerular apparatus.

primary function:

Secretion

From blood plasma to filtrate.

secretes ions

potassium (K+)

acid (H+)

Reabsorption of water also occurs:

influenced by two hormones

Aldosterone

antidiuretic hormone (ADH).

36. 27-36
Collecting Collecting Ducts
Function in a well hydrated person:

transport the tubular fluid into the papillary duct and
then into the minor calyx.
Function in a dehydrated person:

water conservation

more-concentrated urine is produced.
ADH can act on the collecting duct epithelium

Cells become permeable to water

Water moves from filtrate into blood plasma
Involves vasa recta.

37. 27-37
Innervation of the Kidney

innervated by a mass of autonomic nervous
system fibers

called the renal plexus.

The renal plexus

accompanies each renal artery

enters the kidney through the hilum.

38. 27-38
Urinary Tract : Ureters
long, fibromuscular tubes
conduct urine from the kidneys to the urinary bladder.
average 25 centimeters in length
retroperitoneal.
ureters originate at the renal pelvis
extend inferiorly to enter the posterolateral wall of the
base of the urinary bladder.
wall is composed of three concentric tunics.

mucosa

muscularis
adventitia.

39. 27-39
Urinary Tract – Urinary Bladder

The urinary bladder:

expandable, muscular container

serves as a reservoir for urine

positioned immediately superior and posterior to the pubic
symphysis.

in females

the urinary bladder is in contact with the uterus
posterosuperiorly and with the vagina posteroinferiorly.

in males

it is in contact with the rectum posterosuperiorly and is
immediately superior to the prostate gland.

is a retroperitoneal organ.

when empty exhibits an upside-down pyramidal shape.

Filling with urine distends it superiorly until it assumes an
oval shape.

40. 27-40
Urinary Tract – Urinary Bladder

Trigone

posteroinferior triangular area of the urinary bladder wall

formed by imaginary lines

connect the two posterior ureteral openings

and the anterior urethral opening.

The trigone remains immovable as the urinary
bladder fills and evacuates.

It functions as a funnel

directs urine into the urethra as the bladder wall contracts

four tunics

mucosa

submucosa

Muscularis: called the detrusor muscle

adventitia.

Internal urethral sphincter (smooth muscle)

41. 41

42. 42

43. 43

44. 27-44
Micturition (Urination)

The expulsion of urine from the bladder.

Initiated by a complex sequence of events called
the micturition reflex.

The bladder is supplied by both parasympathetic
and sympathetic nerve fibers of the autonomic
nervous system.

45. 27-45
Urethra

Fibromuscular tube

exits the urinary bladder through the urethral opening

at anteroinferior surface

conducts urine to the exterior of the body.

Tunica mucosa: is a protective mucous membrane

houses clusters of mucin-producing cells called urethral
glands.

Tunica muscularis: primarily smooth muscle fibers

help propel urine to the outside of the body.

Two urethral sphincters:

Internal urethral sphincter

restrict the release of urine until the pressure within the
urinary bladder is high enough

External urethral sphincter

and voluntary activities needed to release the urine are
activated.

46. 27-46
Urethra

The internal urethral sphincter

involuntary (smooth muscle)

superior sphincter surrounding the neck of the bladder,
where the urethra originates.

a circular thickening of the detrusor muscle

controlled by the autonomic nervous system

The external urethral sphincter

inferior to the internal urethral sphincter

formed by skeletal muscle fibers of the urogenital
diaphragm.

a voluntary sphincter

controlled by the somatic nervous system

this is the muscle children learn to control when they
become “toilet-trained”

47. 27-47
Female Urethra
Has a single function:

to transport urine from the urinary bladder to the
vestibule, an external space immediately internal to the
labia minora
3 to 5 centimeters long, and opens to the outside
of the body at the external urethral orifice located
in the female perineum.

48. 48

49. 27-49
Male Urethra
Urinary and reproductive functions:

passageway for both urine and semen
Approximately 18 to 20 centimeters long.
Partitioned into three segments:

prostatic urethra is approximately 3 to 4 centimeters long and is the
most dilatable portion of the urethra

extends through the prostate gland, immediately inferior to the
male bladder, where multiple small prostatic ducts enter it

membranous urethra is the shortest and least dilatable portion

extends from the inferior surface of the prostate gland through the
urogenital diaphragm

spongy urethra is the longest part (15 centimeters)

encased within a cylinder of erectile tissue in the penis called the
corpus spongiosum

extends to the external urethral orifice

50. 50

51. 27-51
Aging and the Urinary
System

Changes in the size and functioning of the kidneys begin at
30.

Gradual reduction in kidney size.

Reduced blood flow to the kidneys.

Decrease in the number of functional nephrons.

Reabsorption and secretion are reduced.

Diminished ability to filter and cleanse the blood.

Less aldosterone or antidiuretic hormone.

Ability to control blood volume and blood pressure is reduced.
Bladder decreases in size.
More frequent urination.
Control of the urethral sphincters—and micturition—may be
lost.

52. 52