2. Urinary System
Dr. Raeesa Mohammed
Associate professor of Histology

3. Urinary System Includes: 2 Kidneys. 2 Ureters. Single Urinary bladder.
Single Urethera.

4. Kidney Bean-shaped organ
Covered by dense irregular collagenous connective tissue capsule
Has a lateral convex border & a medial concave border with hilum, where the:
Arteries enter
Ureter & veins leave the kidney

5. Kidney cont’d Each kidney is divided into: Outer Cortex
Inner Medulla: which is composed of renal pyramids
The base of pyramid is toward the cortex, and the apex (renal papilla) toward the hilum
Renal pyramids are separated by cortical tissue called renal columns of Bertin P

6. Kidney cont’d
The apex of each pyramid is perforated by large collecting ducts (papillary ducts of Bellini) that open into the minor calyx
The minor calyx, surrounds the apex of each pyramid
3 or 4 minor calyces join to form a major calyx
The major calyces, 3-4 in number open into the renal pelvis.

7. Nephron It is composed of : Renal corpuscle Proximal tubule
Loop of Henle
Distal tubule

8. Renal Corpuscle Composed of: Glomerulus:
Tuft of fenestrated capillaries. Afferent & efferent arterioles supply & drain the glomerulus at the vascular pole
Bowman’s capsule:
Encloses the glomerulus. It has two layers:
Parietal layer formed by simple squamous epithelium.
Visceral layer formed by podocytes

9. Renal Corpuscle cont’d
Bowman’s (urinary or glomerular) space:
Space between the parietal and visceral layers, drains at the urinary pole into the proximal convoluted tubule
Interstitial tissue is composed of mesengium (mesangial cells & the extracellular matrix manufactured by them)

10. Podocytes Are modified cells with multiple processes and pedicles
Form the visceral layer of Bowman’s capsule
Their processes and pedicles surround the glomerular capillaries.
The spaces between adjacent pedicles, called the filtration slits are covered by slit diaphragms.
Form a thick basal lamina that is interposed between the podocytes and the endothelial cells

11. Glomerular Filtration Barrier
The barrier is formed by:
the podocyte layer of Bowman's capsule
the fenestrated endothelium of the glomerulus
a thick basement membrane shared between the two cellular components
GFB

12. Collecting Tubule Is composed of: Proximal convoluted tubule:
Loop of Henle:
It has 3 regions:
Descending thin limb.
Henle’s loop
Ascending thin limb
Distal convoluted tubule:

13. Proximal tubule:
It is composed of simple cuboidal epithelium with:
Extensive striated or brush border
Thin limb of Henle’s Loop: It is composed of simple squamous epithelium

14. Juxtaglomerular Apparatus
Distal Tubule
It is composed of simple cuboidal epithelium.
Juxtaglomerular Apparatus
It has 3 components:
The macula densa of distal tubule.
Juxtaglomerular cells of glomerular arterioles (modified smooth muscle of tunica media); they secrete renin, angiotensin-converting enzyme and angiotensin.
The extraglomerular mesangial cells called lacis cells.

15. Renal medulla contains:
Collecting Duct
Several distal convoluted tubules join each collecting duct
Are composed of simple cuboidal epithelium.
Renal medulla contains:
Collecting tubules (ducts)
Henle’s loop
Peritubular blood vessels (vasa recta)
Renal interstitium

16. Ureter
Is composed of:
Mucosa: formed of transitional epithelium & lamina propria.
Muscularis (muscular coat): is formed of 2 layers of smooth muscle:
Inner longitudinal
Outer circular
Adventitia: fibrous connective tissue covering

17. Urinary bladder It has the same structure as the ureter, except:
a. The muscularis has 3 layers of smooth muscle, inner longitudinal, middle circular and outer longitudinal.
Serosa/adventitia is outer covering

18. Practical Slides

19. Kidney Cortex

20. Kidney Medulla

21. Urinary Bladder

22. Urinary Bladder

23. Thank U & Good Luck