Question

In which segment of nephron, reabsorption is minimum?
A. Proximal convoluted tubule (PCT)
B. Distal convoluted tubule (DCT)
C. Loop of Henle
D. Both A and B

Answer 1

Hint: To answer this question, if we compare the volume of the filtrate formed per day (i.e. 180 L per day) to that of the urine released (1.5 L), we will see that around 99% of the filtrate must be reabsorbed by the renal tubule system.

Complete answer:
The urine formation occurs in three crucial steps or processes :
> Ultrafiltration or Glomerular filtration
> Selective tubular reabsorption
> Tubular secretion
ULTRAFILTRATION OR GLOMERULAR FILTRATION :
Filtration of blood is the first step in urine formation, which is carried out by the glomerulus.
This process occurs in the Malpighian corpuscle of the nephron. The glomerular capsular membrane (Filtration membrane) through which filtration of blood occurs consists of three layers.
> The endothelium of glomerular blood vessels.
> The epithelium of Bowman's capsule.
> A basement membrane between these two layers.
Podocytes are the cells of Bowman’s Capsule that are arranged just close to each other so as to leave some minute spaces called as slit pores through which almost all the constituents of the plasma except the proteins pass in the lumen of the Bowman's capsule. Thus, it is termed as the process of ultrafiltration.
SELECTIVE TUBULAR REABSORPTION:
The epithelial cells of the tubules in different segments of nephron perform reabsorption of essential ions and compounds by both active and passive mechanisms.
Reabsorption is the maximum PCT.
Reabsorption is minimum in ascending limb of henle.
TUBULAR SECRETION:
It maintains an ionic and acid base balancer in the body.
It is an active process occurring in PCT, DCT and Collecting duct.

Thus the correct option is(c) Loop of Henle.

Note: The plasma fluid that filters out from glomerular capillaries is called glomerular filtrate. It is protein less plasma.