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3 out of 8

What is absent in the medulla?

A Loop of Henle
B Vasa recta

C Collecting duct
D Juxtaglomerular apparatus

Ans. D Juxtaglomerular apparatus :

The juxtaglomerular apparatus is located at the angle of the afferent and efferent arterioles where it comes in contact with the cortical thick ascending limb (CTAL).

It comprises the macula densa, the juxtaglomerular (JG) cells and the lacis (or the extraglomerular mesangial) cells.

Juxtaglomerular apparatus

Components are

  1. Juxtaglomerular cells : These are modified smooth muscle cells in the tunica media of the afferent arteriole. The cells have renin – containing granules.
  2. B Macula densa : This is the modified region of the tubular epithelium; it marks the beginning of DCT
  3. Lacis cells:

Difference between cortical and juxtamedullary nephron

Cortical nephron

Juxtamedullary nephron

1) Form 85% of the nephrons

Form 15% of the nephrons

2) Short loop of Henle

Long loop of Henle

3) Peritubular capillary network is short

Form vasa recta

4) Blood flow is large

Blood flow is less

5) O2 extraction is very less

O2 extraction is large

6) PO2 is 50mmHg

PO2 is 15mmHg