Urinary System Ji-Cheng Li

Components ---kidney : produce urine ---ureters ---bladder -cavity organs, conduct, store and ---urethra remove the urine ---functions: remove waste products of metabolism regulate the homeostasis secrete some bioactive factors - renin, erythropoietin

2. Kidney ---hilum: BV, LV, N and ureters enter or out renal pelvis: funnel-shaped expension of upper end of ureter calyx: branches of renal pelvis

1)   General structure: ---capsule: DCT ---cortex: /medullary ray /cortical labyrinth /renal columns ---medulla: /renal pyramid /renal papillae: -minor calyx -major calyx -pelvis

*renal lobe: one renal pyramid and its bounding cortical tissue *renal lobule: renal tissue including one medullary ray and ½ cortical tissue surround it

According to function, renal parenchyma is mainly consists of uriniferous tubules /uriniferous tubules= renal tubule+ collecting tubules /renal corpuscle = glomerulus + renal capsule (beginning part of renal tubule) /nephron = renal corpuscle + renal tubule ---interstitium: CT, BV, N

juxtamedullary nephron /renal glomerulus: /renal capsule structural and functional unit, 1,000,000 ---renal corpuscle: cortical nephron juxtamedullary nephron /renal glomerulus: /renal capsule

---renal tubule: /proximal tubule: -convoluted portion -straight portion /thin segment /distal tubule:

①  renal corpuscle: spherical, 200um in D, two poles: vascular pole and urinary pole ---glomerulus: afferent arterioles→capillary network →efferent arterioles *capillary network: /endothelial cell: pore, 70-90 nm, no diaphragm /basal lamina: 330nm

*intraglomerular mesangium: /mesangial cell:

-functions: i.   produce ground substance ii.  phagocytosis iii. contract iv. secrete renin and enzymes

---renal capsule: two layers capsule –formed by beginning part of renal tubule which is enlarged and invaginated /parietal layer: simple squamous epi. /visceral layer: podocytes /renel capsular cavity: the space between two layers

*podocyte: cells with many processes (primary and secondary processes-foot processes) Foot processes: interdigitated with each other and embraced the capillaries, slit pore: -narrow intercellular space between foot processes -25 nm, with 4-6 nm diaphragm-slit membrane

---function: produce filtrate by filtration

filtration barrier: fenestrated endothelial cell: negative ions basal lamina slit membrane

②   renal tubule: a. proximal tubule: 50-60um in D, 14 mm long ---structure LM: EM: pyramidal cuboidal eosinophilic round N brush-liked border - microvilli longitudinal striation- plasma membrane infolding no clear boundary - lateral extension (rich in Na+ K+ ATPase)

Proximal tubule

---Function: i. reabsorption : -85% Na+ ions and water -All of glucose, aminoacid, polypeptide, proteins and vitamin ii. secrete H+, NH3, hippuric acid and creatinine

b. thin segment: /10-15 um, simple squamous epi, /facilitate the passage of water and ions /reabsorb Na+ and Cl- and 5% water

c. distal tubule: ---structure: LM: EM: cuboidal slight-stained round N no brush-liked border – less microvilli well-developed longitudinal striation – plasma membrane infolding

Distal tubule Plasma membrane infolding

---function: i.    reabsorption of 8% water, Na+ ions ii.   excretion of K+, H+,NH3 iii. regulated by aldosterone (adrenal gland) and antidiuretic hormone (vasopressin) (pituitary gland)

medullary loop (nephron loop ) proximal tubule , thin segment, distal tubule

3) collecting tubule: arched collecting tubules cortical collection tubules medullary collection tubules -simple cuboidal epi. to simple columnar epi. -slight –stained -have clear boundary -reabsorb 4% water

4)    juxtaglomerular complex

a. juxtaglomerular cell: ---a groups of modified SM cell of afferent arterioles ---structure: -larger, cuboidal in shaped, with round N -contain secretory granules ---function: i.secrete renin→adrenal gland→aldosterone→blood pressure↑ ↑ angiotensinogen→angiotensin I→angiotensin II→contraction of SM of BV ii. secrete erythropoietin to promote erythropoiesis

b. macula densa ---a group of cells derived from epi. of distal tubule ---cell becomes taller, narrow, with round N apical part arranged ---cells have processes connecting with other cells ---function: chemoreceptors- feel the Na+ ions concentration

c. extraglomerular mesangial cell (polar cushion cell) ---similar to intraglomerular mesangial cell ---transfer the information d. peripolar cell ---structure: EM: -microvilli -junctional complexes -RER, Golgi, and granules ---function: regulate the reabsorption and secretion of renal tubule

5) renal interstitial: CT ---fibers: type I,III,IV collagen ---matrix ---cell: fibroblast macrophage lipid-laden interstitial cell: -stellate cell with processes -osmiophilic lipid droplets: -function: i.   involve in formation of F and matrix ii.  secret prostaglandin

6) Blood supply to the kidney i. Very large blood flow (1.2L/min) ii. To form cap.two times iii. Glomerular cap. have a high blood pressure iv. Form vasa recta loop near medullary loop v. More larger blood flow in renal cortex

Interlobar arteries → Arcuate arteries →Interlobular arteries →Capsular cap. ↑ ↓ ↓ Renal artery Afferent arterioles Afferent arterioles ↓ ↓ Juxtamedullary nephron Cortical nephron glomerulus glomerulus Efferent arterioles Efferent arterioles Vasa recta(artery and vein)← Capillary network Capillary network ↓ ↓ ↓ Renal vein←Interlobar vein← Arcuate vein ← Interlobular vein ← Stellate vein

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