Urogenital

1. 26-1
Human Urogenital System

2. 26-2
Urogenital System Functions
•Filtering of blood, Removal of wastes and
metabolites
•Regulation of
–blood volume and composition
–concentration of blood solutes
–pH of extracellular fluid
–blood cell synthesis
•Synthesis of Vitamin D
•Reproduction and sexual function

3. 26-3
Urinary System Anatomy

4. 26-4
Location and External Anatomy
of Kidneys
•Location
–Lie behind peritoneum on
posterior abdominal wall
on either side of vertebral
column
–Lumbar vertebrae and rib
cage partially protect
–Right kidney slightly lower
than left
•External Anatomy
–Renal capsule
•Surrounds each kidney
–Perirenal fat
•Engulfs renal capsule and acts as
cushioning and source of energy
–Renal fascia
•Anchors kidneys to abdominal
wall, separates from abdomen
–Hilum
•Renal artery and nerves enter and
renal vein and ureter exit kidneys

5. 26-5
Internal Anatomy of Kidneys
•Cortex: Outer area
–Renal columns
•Medulla: Inner area
–Renal pyramids
•Calyces
–Major: Converge to form
pelvis
–Minor: Papillae extend
•Nephron: Functional unit
of kidney
–Juxtamedullary
–Cortical

6. 26-6
The Nephron

7. 26-7
Histology of the Nephron

8. 26-8
Internal Anatomy of Kidneys
•Renal corpuscle
–Bowman’s or Renal capsule
•Parietal layer
•Visceral layer
–Glomerulus
•Network of capillaries
goes into another capillary
bed called the peritubular
Capillaries
- Arterioles
–Afferent
•Blood to glomerulus
–Efferent
•Drains not into veinule but
another arteriole
•Tubules
–Proximal (convoluted)
tubule
–Loops of Henle
•Descending limb
•Ascending limb
–Distal (convoluted) tubules
•Collecting ducts

9. 26-9
Renal Corpuscle

10. 26-10
Kidney Blood Flow

11. 26-11
Ureters and Urinary Bladder
•Ureters
–Tubes through which
urine flows from
kidneys to urinary
bladder
•Urinary bladder
–Stores urine
•Urethra
–Transports urine from
bladder to outside of
body
–Difference in length
between males and
females
–Sphincters
•Internal urinary
•External urinary

12. 26-12
Ureters and Urinary Bladder

13. 26-13
Urine Formation

14. 26-14
Filtration
•Filtration
–Renal filtrate
•Plasma minus blood
cells and blood proteins
•Most (99%) reabsorbed
•Filtration membrane
–Fenestrated
endothelium, basement
membrane and pores
formed by podocytes
•Filtration pressure
–Responsible for filtrate
formation
–Glomerular capillary
pressure (GCP) minus
capsule pressure (CP)
minus colloid osmotic
pressure (COP)
–Changes caused by
glomerular capillary
pressure
EFP = GCP – CP – COP
Where Effective filtration pressure = EFP

15. 26-15
Filtration Pressure

16. 26-16
Tubular Reabsorption
•Reabsorption almost 90%
takes place in Proximal
tubule via
–Passive transport
–Active transport
–Cotransport
•Specialization of tubule
segments
•Distal tubule and
collecting duct affected
by hormones like ADH &
Aldosterone
•Substances transported
–Active transport moves
Na
+
across nephron
wall
–Other ions and
molecules moved by
cotransport
–Passive transport
moves water, urea,
lipid-soluble, nonpolar
compounds

17. 26-17
Reabsorption in Proximal Nephron

18. 26-18
Reabsorption in Loop of Henle

19. 26-19
Reabsorption in Loop of Henle

20. 26-20
Tubular Secretion
•Substances enter proximal or distal tubules
and collecting ducts
•H
+
, K
+
and some substances not produced in
body are secreted by countertransport
mechanisms

21. 26-21
Secretion of Hydrogen and
Potassium

22. 26-22
Urine Production
•In Proximal tubules
–Na
+
and other substances
removed
–Water follows passively
–Filtrate volume reduced
•In descending limb of
loop of Henle
–Water exits passively,
solute enters
–Filtrate volume reduced
15%
•In ascending limb of
loop of Henle
–Na
+
, Cl
-
, K
+
transported out of
filtrate
–Water remains
•In distal tubules and
collecting ducts
–Water movement out
regulated by ADH
•If absent, water not
reabsorbed and dilute urine
produced
•If ADH present, water moves
out, concentrated urine
produced

23. 26-23
Filtrate and Medullary
Concentration Gradient

24. 26-24
Medullary Concentration and
Urea Cycling

25. 26-25
Urine Concentration Mechanism
•When large volume of
water consumed
–Eliminate excess
without losing large
amounts of electrolytes
–Response is kidneys
produce large volume
of dilute urine
•When drinking water
not available
–Kidneys produce small
volume of concentrated
urine
–Removes waste and
prevents rapid
dehydration

26. 26-26
Urine Concentrating Mechanism

27. 26-27
Hormonal Mechanisms
•ADH
–Secreted by posterior
pituitary
–Increases water
permeability in distal
tubules and collecting ducts
•Aldosterone
–Produced in adrenal cortex
–Affects Na
+
and Cl
-

transport in nephron and
collecting ducts
•Renin
–Produced by kidneys,
causes production of
angiotensin II
•Atrial natriuretic
hormone
–Produced by heart when
blood pressure increases
•Inhibits ADH production
•Reduces ability of kidney
to concentrate urine

28. 26-28
Effect of ADH on Nephron

29. 26-29
Aldosterone Effect on Distal
Tubule

30. 26-30
Autoregulation and
Sympathetic Stimulation
•Autoregulation
–Involves changes in
degree of constriction
in afferent arterioles
–As systemic BP
increased, afferent
arterioles constrict and
prevent increase in
renal blood flow
•Sympathetic stimulation
–Constricts small arteries
and afferent arterioles
–Decreases renal blood
flow

31. 26-31
Clearance and Tubular Load
•Plasma clearance
–Volume of plasma
cleared of a specific
substance each minute
–Used to estimate GFR
–Used to calculate renal
plasma flow
–Used to determine
which drugs or other
substances excreted by
kidney
•Tubular load
–Total amount of
substance that passes
through filtration
membrane into
nephrons each minute
–Normally glucose is
almost completed
reabsorbed

32. 26-32
Tubular Maximum
•Tubular maximum
–Maximum rate at
which a substance can
be actively absorbed
–Each substance has its
own tubular maximum

33. 26-33
Urine Flow and
Micturition Reflex
•Urine flow
–Hydrostatic pressure
forces urine through
nephron
–Peristalsis moves urine
through ureters
•Micturition reflex
–Stretch of urinary
bladder stimulates
reflex causing bladder
to contract, inhibiting
urinary sphincters
–Higher brain centers
can stimulate or inhibit
reflex

34. 26-34
Micturition Reflex

35. 26-35
Effects of Aging on Kidneys
•Gradual decrease in size of kidney
–Decrease in kidney size leads to decrease in
renal blood flow
•Decrease in number of functional nephrons
•Decrease in renin secretion and vitamin D
synthesis
•Decline in ability of nephron to secrete and
absorb

36. 26-36
Kidney Dialysis