How does the distal convoluted tubule differ from the proximal tubule?

The distal convoluted tubule differs from the proximal tubule in its function, location, and cellular structure.

The proximal convoluted tubule (PCT) and the distal convoluted tubule (DCT) are both parts of the nephron, the functional unit of the kidney. However, they perform different roles in the process of urine formation. The PCT is primarily responsible for the reabsorption of water, glucose, and ions from the filtrate, while the DCT plays a crucial role in the selective reabsorption and secretion of ions to maintain the body's pH and electrolyte balance.

In terms of location, the PCT is the first part of the tubule system and is found in the renal cortex, close to the glomerulus from which it receives the filtrate. On the other hand, the DCT is located further down the nephron, after the loop of Henle, and is also found in the renal cortex.

The cellular structure of the PCT and DCT also differs. The PCT has a brush border of microvilli on its luminal surface, which increases the surface area for reabsorption. The cells of the PCT also have numerous mitochondria to provide the energy required for active transport during reabsorption. In contrast, the DCT lacks a brush border, and its cells contain fewer mitochondria. However, the DCT has more basolateral infoldings, which facilitate the transport of ions between the tubule cells and the interstitial fluid.

Furthermore, the DCT is sensitive to hormones such as aldosterone and antidiuretic hormone (ADH), which regulate its function. Aldosterone increases sodium reabsorption and potassium secretion, while ADH increases water reabsorption. The PCT, in contrast, is not directly regulated by these hormones.

In summary, while both the PCT and DCT are integral parts of the nephron, they differ significantly in their function, location, and cellular structure.