Urinary System

Urinary System

Urinary system Kidneys Ureters Urinary bladder urethra

Kidney

rtex: outer part of kidney, renal columns, cortical labyrinth. dulla: renal pyramids, medullary rays. um: minor calyces,major calyces, pelvis,ureter

cortex and medulla of kidney

glomerulus Renal corpuscle

Bowman’s capsule

nephron Proximal convoluted tubule Descending L.

Renal tubule

Uriniferous Tubules

Loop of Henle Distal convoluted tubule

Collecting tubules

Loop Ascending L.

nephron

Superficial (cortical) nephron:85% in relation to formation of urine

nephron Juxtamedullary nephron:15% in relation to concentration of urine.

nephron It is the structural and functional unit of kidney to form urine. It consists of a renal corpuscle and a complicated renal tubule.

Renal corpuscle nephron

glomerulus Bowman’s capsule Proximal convoluted tubule Descending L.

Renal tubule

Loop of Henle Distal convoluted tubule

Loop Ascending L.

1. Renal corpuscle It has 2 poles: vascular pole and urinary pole.

glomerulus Renal corpuscle

Bowman’s capsule

1 ） glomerulus A tuft of fenestrated capillaries: arterial capillaries between which there has mesangium made up of mesangial cells(MC) and mesangial matrix. 1.Maitenance basement membrane

MC

2.Phagocytosis 3.Contract to regulate the flow of blood

2 ） renal capsule Cup-like, blind end of renal tubule.

Parietal layer ： simple squamous epithelium

Urinary space Visceral layer ： made up of podocytes

3) Podocytes and glomerular filtration barrier Podocyte: has primary processes and secondary processes.

Filtration barrier: structures between blood and urinary space. Fenestrated endothelial cells Basal lemina Glomerular slit diaphragm

glomerular filtration barrier

2. Renal tubule In cortex

Proximal convoluted tubule

Descending L.

Renal tubule

Loop of Henle

Loop Ascending L.

Distal convoluted tubule

In medulla

In cortex

1 ） proximal convoluted tubule

LM: the lumen is irregular. cell: large,cuboidal or pyramidal; cell boundaries are not clear; have brush border on luminal surface; show vertical striations on basal surface.

EM:

show lateral interdigitations between adjacent cells; have numerous microvilli on the luminal surfaces; have infoldings of cytoplasm on basal surface.

Function of proximal convoluted tubule Main site of reabsorption: almost all glucose, amino acid and protein; most of H20,ion etc. Secretion : Na+,NH3,etc.

2 ） loop of Henle

he wall is simple squamous epithelium.

ermeability to ions and water

3 ） distal convoluted tubule The LM:

EM:

lumen is larger and more regular

cells are stained lightly; have distinct cell boundaries; no brush border on free surface; basal striations are obvious.

microvilli are much shorter; no lateral interdigitations developed infoldings of cytoplasm.

Function of distal convoluted tubule Main site for ion exchanging. reabsorption of Na+,H20 and secretion of K+,H+ and NH3.

Renal tubules

3 Collecting tubules Location: in medulla

Epithelium: simple cuboidal epi. Function: concentration of urine.

Formation of urine Filtrate from the blood in glomerulus Primary Urine 180L/d

Renal space

Absorption and excretion of renal tubules

Terminal Urine

Further concentrated by collecting tubules

Flow into the calyces and pelvis ,then leave the kidney

4 Juxtaglomerular complex Juxtaglomerular cells Modified smooth muscle fibers in tunica media of afferent arteriole at its entry to glomerulus. Function: Producing renin and erythropoietin

Macula densa modified epi. of distal convoluted tubule densely packed together at the site of contact with arteriole. Function: Sensing the change of [Na+]

Extraglomerular mesangial cells(lacis cells) Between macula densa and afferent and efferent arterioles. Function: Probably related to transferring information.

Function of renin Juxtaglomerular cells

renin

angiotensinogen

angiotensin-I angiotensin-II

Enzyme secreted by endoepi.C

adrenal cortex secrets aldosterone Increasinge BP reabsorption of Na+ and H2O by distal convoluted tubules and collecting tubules

Juxtaglomerular complex

glomerulus Renal corpuscle

Bowman’s capsule

nephron Proximal convoluted tubule Descending Limb

Renal tubule

Uriniferous Tubules

Loop of Henle Distal convoluted tubule

Collecting tubules

Loop Ascending Limb.

Ureter and urinary bladder They have 3 layers: Mucosa,muscle layer and adventitia; Transitional epithelium covers their luminal surface.

ureter

Key points 1.Components of nephron and its function. 2.The characteristics of both proximal and distal convoluted tubules under LM and EM. 3.The components of juxtaglomerular complex and their function. 4.The epithelial type of ureter and urinary bladder.