1. Urinary system Histology
Khaleel Alyahya

2. Urinary System
Kidney
Ureters
Urinary Bladder
Urethra

3. Functions Maintain the purity & constancy of internal fluids.
Regulate blood volume.
Produce rennin to help regulate blood pressure.
Produce erythropoietin (hormone) to stimulate RBC production.
Produce urine.

4. Structure of the Kidneys
Kidney is divided into:
Renal Cortex (outer region)
Renal Medulla (inner region)
Cortex
Dark brown and granular
Medulla
6-12 pyramid-shape regions (renal pyramids, NO nephrons)
The base of pyramid is toward the cortex (corticomedullary border)
The apex (renal papilla) toward the hilum that perforated by 12 openings of the ducts of Bellini.
The apex is surrounded by minor calyx.
5 or 8 minor calyces join to form 3 or 4 major calyces that form renal pelvis.
Pyramids are separated by cortical columns of Bertin

5. The Kidneys

6. Cortical Arch Renal corpuscles Convoluted tubules
Medullary rays (cortical continuation of pyramids)

7. Uriniferous Tubule Is the functional unit of the kidney. Is formed of:
1- Nephron
2-Collecting tubule (duct)
They are densely packed.
They are separated by thin stroma and basal lamina
Corpuscles
Convoluted tubules (cortical labyrinth)
Medullary rays (cortical continuation of pyramids)

8. Nephron There are 2 types: Nephron is formed of: Cortical nephrons
Juxtamedullary nephrons
Nephron is formed of:
Renal corpuscle
(cortical & juxtamedullary).
Proximal tubule.
Henle’s loop.
Distal tubule
Note: Collecting tubule (duct) is NOT a part of the nephron!

9. Uriniferous Tubule

10. Uriniferous Tubule

11. Renal Corpuscle Two poles: Glomerulus Bowman’s capsule Mesangial cells
vascular
urinary
Glomerulus
Bowman’s capsule
parietal layer
urinary or glomerular space
visceral layer or podocytes
Mesangial cells
intraglomerular
extraglomerular

12. Renal Corpuscle
Renal cortex
Renal corpuscle

13. Renal Corpuscle

14. Renal Corpuscle

15. Renal Corpuscle

16. Renal Corpuscle

17. Renal Corpuscle

18. Filtration Barrier Endothelial wall of the capillaries Basal lamina
Visceral layer of Bowman’s capsule (podocytes)
Podocytes have primary (major) processes and secondary (minor) processes (pedicles).
Between pedicles (on the surface of capillaries) there are filtration slits that have slit diaphragm

19. Filtration Barrier

20. Proximal Tubule It has 2 regions: Pars convoluta
proximal convoluted tubule
Pars recta
descending thick limb of Henle’s loop
It is composed of simple cuboidal epithilum with acidophilic cytoplasm. The cells have striated or brush border and lateral interdigitations. They have well-defined basal lamina.
Proximal tubules are long and highly convoluted so most of cortical tubular sections are proximal tubules.

21. Proximal Tubule
Cell of proximal tubule

22. Thin limb of Henle’s Loop
It has 3 regions:
Descending thin limb
Henle’s loop
Ascending thin limb
Note:
It is longer in juxtamedullary nephron than in cortical nephron
It is composed of simple squamous epithelium

23. Renal Medulla

24. Distal Tubule It has 3 regions: Ascending thick limb of Henle’s loop
low cuboidal epithelium
Macula densa
1st part, tall & narrow cells
Pars convoluta
distal convoluted tubule formed of low cuboidal epithelium
Distal tubules drain into collecting tubules
Aldosterone hormone increase the active reabsorbtion of sodium from the lumen of tubule into interstitium

25. Distal Tubule
Cell of distal tubule

26. Juxtaglomerular Apparatus
It has 3 components:
The macula densa of distal tubule
Juxtaglomerular cells of afferent glomerular arteriole
modified smooth muscle of tunica media
they secrete renin, angiotensin-converting enzyme and angiotensin
The extraglomerular mesangial cells

27. Juxtaglomerular Apparatus

28. Juxtaglomerular Apparatus

29. Collecting Tubules Are composed of simple cuboidal epithelium
They aren’t part of nephron
They have 3 regions:
Cortical
Medullary
Papillary
They are formed of:
principle cells
intercalated cells
They are impermeable to water except in presence of antidiuretic hormone.

30. Collecting Tubules
Cell of collecting tubule

31. Renal Interstitium It is a very flimsy, scant amount of CT contains.
Fibroblasts.
Macrophages.
Interstitial cells
their nuclei are elongated and they contain lipid droplets
they secrete medullipin I, which is converted in the liver into medullipin II, that lowers blood pressure

32. The Ureters
Mucosa
is formed of transitional epith. and lamina propria.
Muscularis (muscular coat)
is formed of 2 layers of smooth muscle:
inner longitudinal
outer circular
Adventitia (fibrous CT covering)

33. The Ureters

34. The Urinary Bladder It has the same structure as the ureter EXCEPT:
The dome-shaped cells of transitional epithelium have plaques (rigid, thickened regions of plasmalemma)
It has 3 layers of smooth muscle, inner and outer longitudinal and middle circular
Its outer covering is serosa

35. The Urinary Bladder

36. That’s all folks!
Questions?