Urinary System

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

3. UrinarySystem 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: • OuterCortex • Inner Medulla: which is composed of 10-12 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 15-20 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 layerformed by simple squamous epithelium. • Visceral layerformed 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 barrieris 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. Distal Tubule • It is composed ofsimple 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. 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