Question

Mammals can eliminate hypotonic or hypertonic urine according to body needs. Explain.

Answer 1

Hint: Urine formation is the process that releases urea. It maintains the acid-base balance and also plasma composition, osmolarity, and fluid volume are also regulated. Urine contains other substances like gases, glucose, germs, etc.

Complete answer: Mammals have the countercurrent and hormone mechanism which helps in eliminating the hypertonic and hypotonic urine according to the needs of the body. Elimination of hypotonic and hypertonic urine is in the control of the ADH hormone (antidiuretic hormone) and aldosterone. When there are any changes in the body fluid volume, blood volume, and ionic concentration, osmoreceptors in our body get activated. When there is an excess loss of fluid in our body, they activate these receptors which will, in turn, activate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. The antidiuretic hormone will facilitate the water reabsorption from the latter parts of the tubule, which prevents diuresis and thus forms hypertonic urine. When there is an increase in body fluid volume, osmoreceptors are switched off, which suppresses the ADH release to complete the feedback. When ADH is switched off, it facilitates the production of hypotonic urine.

Note: Mammals have inhabited an enormous range of lands on the earth's surface, including some of the most unfavourable lands. When mammals take in a lot of fluid in their food, they excrete more water by producing dilute urine, and when they are in arid regions like high temperatures they retain water by producing highly concentrated urine.