Question

Which tubules stain more darkly and appear fuzzier in a histological preparation of the renal cortex?

1) Proximal convoluted tubules
2) Distal convoluted tubules
3) Collecting ducts
4) Loop of Henle

Answer 1

The proximal convoluted tubules stain more darkly and appear fuzzier in histological preparations of the renal cortex, due to their brush border and high ATP production for active transport.

Step-by-step explanation:

The tubules that stain more darkly and appear fuzzier in a histological preparation of the renal cortex are the proximal convoluted tubules (PCTs). These tubules have prominent microvilli on their luminal surface, forming a brush border that creates a large surface area to maximize absorption and secretion. This histological feature, combined with the presence of numerous mitochondria for ATP production due to active transport of ions across their membranes, gives the PCTs a distinctive dark, fuzzy appearance in histological preparations.