Question

How do skin and lungs contribute in excretion?

Answer 1

In addition to the urinary system, the skin, lungs and liver are accessory excretory organs.

(1) Skin: Human skin possesses glands for secreting two fluids on its surface, namely sweat from the sweat glands and sebum from sebaceous glands. Sweat is a watery fluid containing in solution primarily contains sodium-chloride, lactic acid, urea, amino acids and glucose. It helps in excreting mainly water and sodium chloride, and a small amount of urea and lactic acid. Sebum is a wax-like secretion which helps to excrete some lipids such as waxes, sterols, other hydrocarbons and fatty acids on the skin.

(2) Lungs: Lungs which are the main respiratory organs of vertebrates, help to eliminate the entire volume of carbon dioxide produced in the body, as well as some moisture, during expiration. The lungs maintain the blood-gas homeostasis through the elimination of carbon dioxide.