Urinary SystemUrinary System

Ji-Cheng LiJi-Cheng Li

1. 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, erythr

opoietin

2. Kidney2. 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

---parenchyma:

/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

2) Nephron:

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

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

  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 layer

s

• cells with many processes (primary and secondary processes-foot proces

ses)• Foot processes: interdigitated with each other

and embraced the capillaries, • slit pore: -narrow intercellular space between foot pro

cesses -25 nm, with 4-6 nm diaphragm-slit membran

e

*podocyte:

---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 )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 tub

ule---cell becomes taller, narrow, with round N apic

al part arranged---cells have processes connecting with other c

ells---function: chemoreceptors- feel the Na+ ions c

oncentration

c. extraglomerular mesangial cell (polar cushion cell)

---similar to intraglomerular mesangial cell---transfer the informationd. peripolar cell---structure: EM: -microvilli -junctional complexes -RER, Golgi, and granules---function: regulate the reabsorption and secret

ion 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 timesiii. 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

Thanks!Thanks!