Ahmed Sadawi: Histology of Kidney

Functional Units

of the Kidney

# Histologicaly, kidney consists of:

* Cortex: the outer part # granular cuz of glomeruli.

* Medulla : the inner part # striated cuz of tubules.

* Kidney lobule ----> papillae ----> minor calyx ----> major calyx ----> renal pelvis ----> ureter.

Stroma :
1- Capsule
2- Reticular fibers
3- Collagenous and elastic fibers
Parynchema: uroniferous tubules:
1- nephron
2-collecting tubule

The nephron cosists of:
1- Renal corpuscle: # glomerulus # Bowman's capsule.
2- proximal tubule
3- loop of Henle's
4- distal tubule

# Nephron is functional unit of the kidney.

Diagram of renal corpuscle structure:

A – Renal corpuscle
B – Proximal tubule
C – Distal convoluted tubule
D – Juxtaglomerular apparatus
1. Basement membrane (Basal lamina)
2. Bowman's capsule – parietal layer
3. Bowman's capsule – visceral layer
3a. Pedicels (Foot processes from podocytes)
3b. Podocyte

4. Bowman's space (urinary space)
5a. Mesangium – Intraglomerular cell
5b. Mesangium – Extraglomerular cell
6. Granular cells (Juxtaglomerular cells)
7. Macula densa
8. Myocytes (smooth muscle)
9. Afferent arteriole
10. Glomerulus Capillaries
11. Efferent arteriole

# Bowman's Capsule: consists of 2 layers:
1- Parietal layer: simble squamous epi. 2
2- Visceral layer: Podocytes 3
# Mesangial cells : # macrophages # supporting cells # part of juxtaglomerular apparatus.
# Proximal tubules : # cubical # wider in diameter # narrower lumen # cells with microvilli # section shows 3-5 cells # cells are indistinct.
# Distal tubules : # cubical # wider in lumen # narrower diameter # cells without microvilli # section shows 5-8 cells # cells are distinct.
# Juxtaglomerular apparatus : # consists of:
1- JG cells: modified SM cells of afferent arteriole.
2- Macula densa: modified cells of distal tubule.
3- Polar cushion: extrglomerular mesangeal cells.
# function of JGA : secretion of Renin
Angiotensinogen ---> angiotensin I ---> angiotensin II