AEMCA Practice Exam

In which part of the renal tubule does most reabsorption occur?

1. Distal convoluted tubule

2. Proximal convoluted tubule

3. Loop of Henle

4. Collecting duct

The correct answer is: Proximal convoluted tubule

Most reabsorption in the renal tubule occurs in the proximal convoluted tubule (PCT). This segment is specifically designed for the efficient reclamation of valuable substances from the filtrate back into the bloodstream. Approximately 65-70% of the filtered water, sodium, and a significant percentage of other nutrients, such as glucose and amino acids, are reabsorbed here. The structure and cellular mechanisms of the PCT facilitate this process, with numerous microvilli increasing the surface area for absorption and a variety of transport proteins aiding in the movement of solutes. Because of these adaptations, the PCT plays a crucial role in maintaining the body’s fluid and electrolyte balance. In other parts of the renal tubule, such as the distal convoluted tubule, the loop of Henle, and the collecting duct, reabsorption still occurs but to a lesser extent compared to the PCT. For example, the distal convoluted tubule is primarily involved in the adjustment of salt and water reabsorption under hormonal influence, while the loop of Henle is important for the concentration of urine. The collecting duct focuses on the final adjustments of water reabsorption regulated by hormones like antidiuretic hormone (ADH). Thus,