1. Urinary System Li Jinxin, associate professor No.1020603
Department of Histology and Embryology

2. Objectives 1.Structure and function of each component of a nephron.
2.Ultrastructure of the filtration
barrier of the renal glomerulus.
3.Components, structure and function
of the juxtaglomerular complex.

3. Urinary System Components Functions:
kidney,ureters,bladder,urethra
Functions:
remove waste products of metabolism
regulate the homeostasis
secrete some bioactive factors

4. 1. Kidney 1.1 General structure capsule: DCT parenchyma:
cortex: medullary ray
cortical labyrinth
renal columns
medulla: renal pyramid
interstitium: CT, BV, N

5. According to function, renal parenchyma is made up of numerous nephron and collecting duct. A nephron consists of two components: the renal corpuscle and the renal tubule. Each renal tubule and collecting duct is made up of numerous epithelial-line tubules termed uriniferous tubules.

6. cortical labyrinth
cortex
medullary ray
medulla

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

8. 1.2 Nephron
The nephron is the structural and functional unit of the kidney, composed of two parts:renal corpuscle and renal tubule.
There are about one to two million nephrons in each kidney.
Depending on the location of the renal corpuscle ,nephrons may be classified as cortical or juxtamedullary nephron.

9. renal corpuscle:
renal glomerulus
renal capsule
renal tubule:
proximal tubule:
--convoluted portion
--straight portion
thin segment
distal tubule:

10. 1.2.1 renal corpuscle spherical, 200µm in diameter.
two poles: vascular pole and urinary pole
two parts: glomerulus
renal capsule (Bowman’s capsule)

11. renal corpuscle Afferent arteriole Efferent arteriole Vascular pole
Bowman’s capsule
Capillary network
Podocyte
Parietal layer
Urinary pole

12. 1.2.1.1 glomerulus afferent arterioles→capillary network
→efferent arterioles
capillary network:
endothelial cell: pore, nm
no diaphragm

13. intraglomerular mesangium
mesangial cell:
LM:small, irregular, with processes
EM: RER, Golgi, lysosome
phagocytic vesicles
Functions:
i.   produce ground substance
ii.  phagocytosis

14. 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

15. Primary process
Secondary process
Slit pore
Slit membrane
podocyte

16. basal lamina
basal lamina: 330nm
type IV collagen, proteoglycan

17. filtration barrier or membrane
the structure for filtration is located between the podocytes and the endothelial cells of the glomerulus.
including:
fenestrated
endothelial cell
basal lamina
slit membrane

18. 1.2.2 renal tubule proximal tubule convoluted portion straight portion
50-60µm in D, 14 mm long
proximal tubule
convoluted portion
straight portion
thin segment
distal tubule

19. proximal tubule
LM structure
pyramidal or cuboidal
eosinophilic
round nuclear
brush border
longitudinal striation
no clear boundary

20. plasma membrane infolding lateral extension
EM structure:
Microvilli
plasma membrane infolding
lateral extension

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

22. thin segment
10-15 µm
simple squamous epithelial.
facilitate the passage of water and ions

23. LM structure: cuboidal slight-stained round nuclear no brush border
distal tubule
LM structure:
cuboidal
slight-stained
round nuclear
no brush border

24. EM structure:
less microvilli
well-developed longitudinal striation
plasma membrane infolding
Function:
i.   reabsorption of 8% water, Na+ ions
ii.  excretion of K+, H+,NH3

25. Arched collecting tubules Straight collecting tubules Papillary ducts
Epi. From simple cuboidal to simple columnar
slight –stained
have clear boundary
Function:reabsorb water

26. 1.4 Juxtaglomerular complex
It is located at the vascular pole of the renal corpuscle.
It consists of three structures: juxtaglomerular cell, macula densa and extraglomerular mesangial cell.

27. structure: larger, cuboidal in shaped, contain secretory granules.
1.4.1 juxtaglomerular cell
Juxtaglomerular cells are derived from smooth muscle cells in the wall of the afferent arteriole.
structure: larger, cuboidal in shaped, contain secretory granules.
function:
i. secrete renin
ii. secrete erythropoietin

28. 1.4.2 macula densa
a group of cells derived from epithelium of distal tubule.
cell becomes taller, narrow, with round nuclear apical part arranged.
cells have processes connecting with other cells.
function: chemoreceptors
feel the Na+ ions concentration.

29. 1.4.3 extraglomerular mesangial cell
(polar cushion cell)
similar to intraglomerular mesangial cell
transfer the information

30. 1.5 Blood supply to the kidney (self-study)
Very large blood flow (1.2L/min)
To form cap.two times
Glomerular cap. have a high blood pressure
Form vasa recta loop near medullary loop
More larger blood flow in renal cortex

31. 2. Urinary bladder (self-study) 2.1 Mucosa
epithelium：transitional epithelium
lamina propria
2.2 Muscularis
2.3 Adventitia

32. questions 1.state the conception and components of nephron?
2.describe the components and structure of
renal corpuscle.
3.state the conception and components of
filtration barrier?
4.Name the components of the juxtaglomerular
complex ,and describe their structure and
function.