**Question:** Characteristic feature of cells of collecting duct are

A. Enlarged nucleus
B. Presence of brush border
C. Presence of basal infoldings
D. Presence of microvilli

**Correct Answer:**

**Core Concept:**

Collecting ducts are part of the nephron, the basic functional unit of the kidney responsible for filtering blood and producing urine. Cells within the collecting duct are specialized to perform specific functions related to urine concentration and dilation.

**Why the Correct Answer is Right:**

The correct answer, option C, highlights the presence of basal infoldings in the cells of the collecting duct. Basal infoldings are folds or invaginations of the basal membrane, which increase the surface area for selective reabsorption of ions and water, thereby facilitating urine concentration.

**Why Each Wrong Option is Incorrect:**

A. Enlarged nucleus (option A) is not a defining feature of collecting duct cells, as the nucleus is typically larger in cells involved in active transport processes like the principal cells of the nephron.

B. Presence of brush border (option B) is characteristic of the principal cells of the nephron, which are responsible for active reabsorption of ions and glucose. Collecting duct cells, on the other hand, are involved in passive reabsorption and secretion processes.

D. Presence of microvilli (option D) is a feature of enterocytes, the cells lining the small intestine, not collecting duct cells. Microvilli are involved in passive absorption of nutrients and ions.

**Clinical Pearl:**

Understanding the specific cellular features of different nephron segments is crucial for understanding kidney function and pathology, particularly in the context of fluid, electrolyte, and acid-base balance regulation. These features are also essential for interpreting clinical images like kidney histology slides and understanding the pathophysiology of kidney diseases affecting these cells.