Question

How is the proximal convoluted tubule different from the distal convoluted tubule?

a. The proximal convoluted tubule is parallel to the vasa recta, just like the distal convoluted tubule.
b. The proximal convoluted tubule has numerous aldosterone-regulated solute transport mechanisms, just like the distal convoluted tubule.
c. Water reabsorption is always obligatory in the proximal convoluted tubule but not in the distal convoluted tubule.
d. The proximal convoluted tubule empties directly into the collecting duct, just like the distal convoluted tubule.

Answer 1

\ The distal convoluted tubule (DCT) follows the loop of Henle, has fewer microvilli, fewer mitochondria, and is influenced by aldosterone for further sodium and potassium reabsorption and secretion. The correct option is A.

Step-by-step explanation:

The proximal convoluted tubule (PCT) and the distal convoluted tubule (DCT) differ in several aspects concerning their structure and function within the kidney's nephron.

The PCT is the portion of the nephron that first receives the filtrate from Bowman's capsule. It has a tortuous path and is lined with simple cuboidal cells that have prominent microvilli on the luminal surface, which greatly increases the surface area for reabsorption and secretion of solutes like Na+, Cl-, and glucose.

These cells are highly active, containing many mitochondria to produce ATP for active transport.

In contrast, the DCT is located after the loop of Henle and is also tortuous and lined by simple cuboidal epithelium but it is shorter than the PCT and the cells have fewer microvilli.

The DCT cells have fewer mitochondria than PCT cells, reflecting their lower activity in reabsorption and secretion. In the DCT, aldosterone plays a crucial role by increasing the amount of Na+/K+ ATPase in the basal membrane, facilitating further reabsorption of Na+ and secretion of K+ before the forming urine enters the collecting ducts. The correct option is A.