Renal cortex has a dotted appearance and Renal medulla has a striped appearance. Explain.
Topic: Appearance of renal cortex and medulla
Answer
The CORTEX appears DOTTED because it contains the rounded MALPIGHIAN CAPSULES (Bowman’s capsules with their glomeruli) and the coiled proximal and distal convoluted tubules, which appear as dots in section.
The MEDULLA appears STRIPED because it contains the straight, parallel parts of the nephron — the LOOPS OF HENLE and the collecting ducts — which run in the same direction and so look like stripes.
The appearance follows directly from the SHAPE of the structures in each region, and saying so is what earns the marks.
ROUNDED and COILED structures cut across in section look like DOTS — hence the cortex. STRAIGHT PARALLEL tubes look like STRIPES — hence the medulla.
This also fixes the arrangement of the nephron, which is examined repeatedly: the MALPIGHIAN CAPSULES lie in the CORTEX (the outer region) and the LOOPS OF HENLE dip into the MEDULLA (the inner region).
The logic is worth holding: filtration happens where the blood arrives, at the outside; concentration happens as the filtrate travels inwards.