Question

The ability to produce concentrated (hypertonic) urine in vertebrae generally depends on
A. Area of bowman's capsule Epithelium
B. Length of the proximal convoluted tubule
C. Length if Henle's loop
D. Capillary network forming glomerulus

Answer 1

Hint: The capability of the kidney to produce urine that is hypertonic to the blood plasma is due to the loop of Henle. The loop of Henle does not concentrate the urine directly, instead, it functions as a countercurrent multiplier creating a concentration gradient in the surrounding medulla.

Complete answer:
> Option A: Bowman's capsule performs the first step in the filtration, known as ultra-filtration of blood to form urine. The glomerular filtration rate (GFR) is the rate at which blood is filtered through all of the glomeruli. It is the measure of the overall renal function.

> Option B: The proximal convoluted tubule (PCT) regulates the pH of the filtrate in the kidneys. This is done by exchanging hydrogen ions in the interstitium for bicarbonate ions in the filtrate.

> Option C: Henle's loop is accountable for the concentration of urine. The descending limb is impenetrable to electrolytes and water is absorbed into the surrounding tissue, making the urine more concentrated as it descends. So, the longer Henle's loop is, the more concentrated the urine will be.

> Option D: The nutrients in the blood are always absorbed by the capillary network (glomerulus) after filtration.

Hence, the correct answer is option (C).

Note: Excretion of excess water leads to a formation of hypotonic urine whereas excretion of excess solutes results in a formation of hypertonic urine. The urine is hypotonic to the blood but hypertonic to the external medium. The concentration of urine may differ in the two antennary glands.