Question

Following ingestion of a large quantity of water by a healthy student, which of the following is correct?

1. Peritubular fluid around the collecting duct is approximately equal in osmolarity to the tubular fluid in the collecting duct
2. Peritubular fluid around the collecting duct at the tip of the renal pyramid is markedly higher in osmolarity compared to the tubular fluid in the collecting duct
3. Tubular fluid at the end of the thick ascending limb is equal in osmolarity to the peritubular fluid at the tip of the renal pyramid
4. The tubular fluid in the tip of the descending limb has a markedly lower osmolarity compared to the peritubular fluid in the cortex

Answer 1

ANSWER :

If a healthy individual drinks a large amount of water then blood plasma volume increases significantly, and secretion of antidiuretic hormone (ADH) from posterior pituitary reduced consequently, which further lead to decreased water reabsorption in distal convulated tubule (DCT) and collecting tubule, as the result peritubular fluid around the collecting duct at the tip of renal pyramid becomes markedly higher in osmolarity than the tubular fluid in collecting duct due to excess amount of water. Hence option (b) is the correct answer.