Understanding the Urinary System: Kidney Anatomy & Function

2. HistologyLecture 17 Urinary System

3. Urinary System The urinary system is composed of: • Kidneys • Ureters • Bladder • Urethra

4. Kidney • Hilum where • Nerves, vessels enter and exit • Ureter exits • Ureter expanded here and form renal pelvis • 150g

5. Kidney • Thin renal capsule • Cortex • Medulla: • Pyramids: 10-15 • Renal papillae (ducts of Bellini) • Adjacent pyramids separated by material like the corex, known as cortical column (of Bertin)

6. Kidney • Three type of substances observed in the cortex • Renal corpuscles ( Red dot-like granules) • Cortical labyrinth (Convoluted tubules) • Medullary rays (Longitudinal striations) • Medullary rays • Kidney lobe • Kidney lobule

10. Uriniferous Tubules Uriniferous Tubules is the functional unit of the kidney, composed of a nephron and a collecting tubules Nephron • About 2 million in each kidney • Nephron is composed of • Renal corpuscle with glomerulus • Proximal convoluted tubule • Thin & thick loops of Henle • Distal convoluted tubule • 2 different types of nephrons: cortical & juxtamedullary

13. Renal Corpuscle • It is an oval to round structure that has about 0.2mm • Composed glomerulus • Bowman’s capsule • visceral layer • Parietal layer • Urinary space • Has 2 pole

14. 45 - 20 - 10 =15

17. 100 nm 6 nm 25 nm

21. Mesengial cells Contractile like Pericytes Receptor for Ang.II & NF Structural support Secretion of ECM Endocytosis like macrophage

23. PCT

25. Proximal Convoluted Tubule PCT • Simple cuboidal epithelium • Thick brush border, intricate lateral border processes, and basement membrane • Acidophilic cytoplasm • Absorb macromolecules from glomerular ultra filtrate, and some ion transport • 67% to 80% of Na, Cl and water • All glucose, amino acids and proteins resorbed • Secretion of Cratinine, H+ • Produce Vit D

27. Loop of Henle

28. Loop of Henle • Loop of Henle has 15-20 micrometer in diameter composed of simple squamous cells • Thick descending limb similar to PCT, Thin descending limb, Thin ascending limb, Thick ascending limb similar to distal convoluted tubule • Thin segment in cortical nephron is short (1-2mm) but long in juxtamedullary (10 mm) so extended deep into medulla and make Henle’s loop • Thin limb resemble capillaries in sections • Thin limb has short microvilli, basal process that interdigitate with adjacent cells • Descending thin limb is highly permeable to water and so to urea NaCl and other ions

30. Distal Convoluted Tubule • It has 2 parts: pars recta and pars convoluta • It is lined by ? • Narrower cells • Have Na-K pumps that respond to Aldosterone • secretes H+ and NH4+ into tubular urine • Macula densa region near glomerulus

33. Macula Densa • Macula densa is a specialized region of DCT • Cells sensitive to Cl inside tubule • When Cl is high ,causes contriction of afferent arteriole • Also may regulate renin release by juxtaglomerular cells

34. Macula Densa & DCT

36. Juxtaglomerular Apparatus • Juxtaglomerular apparatus has 3 components: • Macula densa • Juxtaglomerular cells of afferent arteriol • Extraglomerular mesangial cells( polkissen or lacis cell)

39. Collecting Tubules and Ducts • Collecting tubules and ducts are not part of nephron • Collecting tubules • Principal cells reabsorbing H2O & Na • Intercalated cells(dark cell) with apical vesicles, reabsorbing K, secretion of H or HCO3 • Papillary collecting ducts(ducts of Bellini) 200 to 300 µm open at area cribrosalined by tall columnar principal cells only • ADH

41. Renal interstitium • Cortex loose CT housing fibroblasts and macrophages • Medulla loose CT housing fibroblasts, macrophages, and interstitial cells • Interstitial cells numerous between ducts of Bellini • These cells have elongated nuclei and many lipid droplet • These cells Synthesize of Medullipin I converted by liver to Medullipin II a vasodilator

42. Renal Circulation

46. Calyx • The renal papilla fits into minor calyces, this portion of papilla lined by transitional epithelium • Epithelium is supported by loose CT of lamina propria, deep to it there is a coat of smooth muscle cells Ureter • Mucosa with several folds composed of transitional epithelium 3-5 cell layers supported by a dense irregular CT(lamina propria) • Smooth muscle: inner longitudinal , and outercircular layers, in distal one third an outer longitudinal layer added to other two layers • Fibrous outer coat of CT is not remarkable

48. Bladder • Mucosa lined with transitional epithelium • Plasmalemma of surface epithelial cells composed of mosaic of specialized, rigid, thickened regions known as plaques that lie between normal cell membrane (interplaque regions) • Tight junctions and desmosomes between cells seal paracellular pathways • Lamina propria of dense irregular CT • Smooth muscle runs in random directions except at neck where 3 layers may be detected: inner longitudinal, middle circular and outer longitudinal layers • Outer adventitia or serosa • Urethra is covered in reproductive system lectures

50. Department of Anatomical Sciences Arak Medical University M. Bayat 88/2/19 88/10/2 89/2/25 90/9/28 94/2/28 94/2/29