Question

Describe the role of liver, lungs and skin in excretion.

Answer 1

Excretion is the process of removing harmful and waste materials out of the living body. In this process the animal body involves various organs. In higher animals, the kidney plays a major role in eliminating nitrogenous wastes. Liver, lungs and skin also involve in the excretion too.

Complete Answer:
Excretion is obtained as the process of elimination of harmful and waste by products of the body to maintain proper balance of vital and non-vital materials inside the body. Excretion processes in higher animals mainly involve secondary excretion by liver, lungs and skin.

Excretion by liver: Liver helps to break down the harmful substance for detoxification. It helps to convert amino acids (proteins) into ammonia and pyruvate. Ammonia is highly toxic nitrogenous waste. It needs to be converted into urea so our kidney could eliminate it with urine. Liver also separates the dead RBCs from our circulatory system. It helps to convert cholesterol, skatole and indole into less harmful metabolic substances, which could further be removed by the kidney through excretion.

Excretion by lungs: Lungs are the main respiratory organ of terrestrial animals. In the process of respiration, oxidation of glucose from the $C{O_2}$ as a toxic waste product of our body which further dissolves into blood plasma from tissues. This $C{O_2}$ is eliminated during exhalation in breathing. Lungs ensure the proper amount of oxygen into the blood and also ensure the amount of $C{O_2}$ in blood.

Excretion in skin: Skin is the biggest oxygen of our body (human body). Skin contains some glands which also help humans excrete their excess water and salt substances out of the body, skin has sweat glands which eliminate the water with some inorganic salts (mainly $NaCl$) and lactic acids. This sweat gland by sweating process helps to maintain body temperature too. Our skin also contains sebaceous glands (oil glands) which helps to eliminate the harmful fat from our body.

Note: Liver, lungs, skin and kidney all these organs are involved in the excretion process in all the higher animals like humans. In plants, oxygen is the byproduct of excretion and is released through stomata and root cell walls, among other sources.