Urinary System

Contents

1 kidney

2 ureter and urinary bladder

3 key points

kidneycortex ， medulla ， hilum ， renal pelvis ， pyramid ，medullary ray ， renal column ， major (minor) calyx,cortical labyrinth

General structure of kidney

capsule

kidney

parenchyma

cortex

medulla

Medulla Cortex

cortex

medulla

nephron

renal corpuscle

renal tubule

glomerulus

renal capsule (Bowman’s capsule)

Proximal tubule

Distal tubule

Thin segment

Proximal convoluted tubule

Proximal straight tubule

Distal convoluted tubule

Distal straight tubule

uriniferoustubule

Cortical collecting tubuleCollecting tubule

Medullary collecting tubule

Arched collecting tubule

1. nephron

Definition: It is the structural and functional unit of kidney.

It consists of renal corpuscle and renal tubule.Function: producing urine.

Classification: cortical nephron juxtamedullary nephron

Cortical nephron

Juxtamedullary nephron

Composition of nephron

nephron

renal corpuscle

renal tubule

glomerulus

renal capsule (Bowman’s capsule)

Proximal tubule

Distal tubule

Thin segment

Proximal convoluted tubule

Proximal straight tubule

Distal convoluted tubule

Distal straight tubule

1) renal corpuscle

Consisting of renal capsule (bowman’s capsule)and glomerulus. Each renal corpuscle has one vascular pole and one urinary pole.

(1) glomerulusA tuft of arterial capillary, belongs to fenestrated capillary,Mesansium can be found between capillaries.Mesansium is composed of mesangial cells and matrix

Mesangial cell

phagocytosis ；

Secretion of IL-1,etc ；

Contraction ；

Structural support

(2) renal capsule

Renal capsule

Parietal layer:Made up of Simple squmous epithelium

Visceral layer:Made up of podocytes

Formation: the blind end of renal tubule invaginates and surrounds the glomerulus.

podocyte large cell with many processes (primary processes and secondary

processes)

filtration slits between secondary processes is covered by filtration sl

it membrane.

(3) Filtration membrane

Filtration membrane

Fenestratedendothelium

Basement lamina

Filtration slit membrane

Fenestrated endothelial cell Secondary process primary process cell body of podocyte

Primary process

Secondary (foot) process

Filtration slit membrane

Basement lamina

EndotheliumFiltration membrane

2) Renal tubule

renal tubule

Proximal tubule

Distal tubule

Thin segment

Proximal convoluted tubule

Proximal straight tubule

Distal convoluted tubule

Distal straight tubule

Loop of

Henle

(1) proximal convoluted tubule

(PCT)Its lumen is irregular.

LM:PCT is lined with simple epithelium.Cell are large ， cuboidal or cone in shape and stained intensely.The boundary between adjacent cells is obscure,with brush border on the free surface and basal striations on the basal surface.

EM: Lateral 相邻细胞有侧突相嵌合，Microvilli on the free surface;Basal interdigitations on the basal surface.

Function ： main site for reabsorption of glomerular filtrate. secretion and excretion ：Ｈ＋、 NH4 ＋

Microvilli and basal interdigitation

Basal interdigitation

(2) thin segment

Its wall is made up of simple squamous epithelium.

Without brush border

H2O and ions are easier to transmit.

(3) distal convoluted tubuleDCT

DCT ： with regular ,larger lumen.

LM: PCT is lined with simple cuboidal epithelium.Cells are small and stained intensely.The boundary between adjacent cells is clear,without brush border on the free surface, with obvious basal striations on the basal surface

EM: short microvilli on free surface. basal interdigitations are more developed.

Function ： main site for ions exchange.

Distal convoluted tubule

Distal convoluted tubule

Renal tubules

2 collecting tubule

Function ： further reabsorption of H2O and exchange of ions, making urine more concentrated. 1~2L/h glomerular filtrate

Cortical collecting tubuleCollecting tubule

Medullary collecting tubule

Arched collecting tubule

Collecting tubule

Collecting tubule

3. juxtaglomerular complex

It consists of juxtaglomeru

lar cell, macula densa, extr

aglomerular mesangial cel

l and peripolar cell at vasc

ular pole.

1) juxtaglomerular cell

It is the modified smooth muscle fiber in the tunica media

of afferent arteriole at vascular pole.

Function ： producing renin.

angiotensinogen-------angiotensinⅠ--------angiotensinⅡ

secreting erythropoietin

ACE

2) macula densa• Epithelial cells of DCT become taller and narrower and

arranged compactly near juxtaglomerular cells.

•Function ： sensing the concentration change of Na+ ion in distal tubules.

macula densa

[Na+ ] in distal tubule -------- juxtaglomerular cell secreting renin--

-- reabsorption of Na+ in distal tubule and collecting tubule--- blood [Na+ ]

3) extraglomerular mesangial cell

In the triangle area between afferent and efferent arterioles,

similar to intraglomerular mesangial cells and continuous with them.

Function: similar to that of intraglomerular mesangial cells.

4) peripolar cell

at the site where visceral layer and parietal layer of renal capsule joint.

juxtaglomerular complex

nephron

renal corpuscle

renal tubule

glomerulus

renal capsule (Bowman’s capsule)

Proximal tubule

Distal tubule

Thin segment

Proximal convoluted tubule

Proximal straight tubule

Distal convoluted tubule

Distal straight tubule

uriniferoustubule

Cortical collecting tubuleCollecting tubule

Medullary collecting tubule

Arched collecting tubule

Ureter and urinary bladder They both have 3 layers:mucosa,muscle layer and adventitia.Their luminal surfaces are covered by transitional epithelium.

Key points

1 the structure of nephron

2 the structure of PCT and DCT under LM and EM

3 the composition of juxtaglomerular complex and their functions

4 the type of epithelium covering the luminal surface of ureter and urinary bladder