Question

a) How does the kidney assist in maintenance of water balance in the human body?

b) On a hot summer day, you do not seem to produce much urine as you would otherwise. Explain why?

c) Why is urine yellow in colour?

d) What would happen if you do not drink water for 24 hours in a hot summer month? [5 MARKS]

Answer 1

a) 2 Marks
b) 1 Mark
c) 1 Mark
d) 1 Mark

a) The kidney helps in osmoregulation by regulating the water content of the body. Thus excess water in the blood leaves the glomerulus to enter into the Bowman's capsule. Some of this water is reabsorbed in the loop of Henle and the proximal convoluted tube to maintain a fairly constant composition of blood.

b) On hot days or when the body overheats, the skin gives out water in the form of perspiration to maintain the normal body temperature. This water forms a layer on the surface of the skin and on evaporation cools it. This loss of water through the skin reduces the quantity of water available for urine formation. Hence less urine formation takes place on hot days.

c) Urine is yellow in colour due to the presence of a pigment urochrome, formed due to the breakdown of haemoglobin of old R.B.Cs.

d) During summers, water is constantly eliminated as sweat. The salts are also eliminated along with water. If water is not taken for 24 hours in a hot summer month, it will lead to the dehydration of the body. The shortage of water also causes hyponatremia and hypocalcemia. One feels mental tiredness.