Question

Differentiate between a proximal convoluted tubule and distal convoluted tubule (on basis of their position).

Answer 1

Nephrons are the functional units of the kidney. It has two parts: glomerulus and the renal tubule. The renal tubule begins with a double walled structure called the bowman’s capsule. It further continues to form a highly coiled proximal convoluted tubule (PCT), followed by a Henle’s loop (LOH). It continues to form again a highly coiled structure called a distal convoluted tubule (DCT).

Complete step by step answer:
The tubular cells secrete substances like ${H^ + }$, ${K^ + }$, $N{H_3}$ into the filtrate and helps in maintenance of ionic and acid-base balance of body.
- PCT : It is made of simple cuboidal brush border epithelium and maximum reabsorption occurs here. Nearly all essential nutrients, $70 - 80\%$ electrolytes and $100\%$ glucose are absorbed. PCT helps in maintaining the ionic balance of body fluids by selective secretion into filtrate.
- LOH : It has $2$ limbs, Descending limb which is permeable to water and concentrates the filtrate as it moves down. The ascending limb is permeable to electrolytes and impermeable to water and dilutes the filtrate as it again moves upwards. Reabsorption is minimum in ascending limb. The filtrate then reaches DCT.
- DCT : Conditional reabsorption of $N{a^ + }$ and ${H_2}O$ occurs here. Aldosterone, a mineralocorticoid from the zona glomerulosa of the adrenal cortex, acts on DCT to promote NaCl absorption.
- CD : The filtrate from DCT reaches CD where Antidiuretic Hormone (ADH) from posterior pituitary promotes the absorption of water, thereby releasing the concentrated urine.
Hence, the PCT and DCT are present in the cortex region of the kidney.

Note: Glomerulus is a tuft of capillaries, formed by the afferent arteriole (a branch of renal artery) and it is carried away by the efferent arteriole. Glomerulus and Bowman’s capsule are together called the Malpighian body/ corpuscle. The nephrons are of two types, cortical nephrons, in which the loop of Henle is too short and extends little into the medulla, while the ones with longer loop of Henle are called juxta medullary nephrons.