Question

How do skin, lungs and liver help in excretion in mammals?

Answer 1

Excretion

1. Excretion is the process of eliminating toxic substances produced as a result of different metabolic processes going on in the body.
2. Majority of these wastes are nitrogenous and are extremely toxic.
3. Although kidneys are the main excretory organs the liver, skin, and lungs also play a role in the excretion of metabolic wastes.

Liver

1. Amino acids produced by the digestion of the protein are broken down in the liver.
2. One of the immediate products of amino acid breakdown is ammonia. It is highly toxic and needs a large amount of water to get eliminated.
3. Liver converts the ammonia to urea, a comparatively less toxic form of nitrogenous waste that can be eliminated through urine.
4. Breakdown of RBC produces bile pigments which are added to bile juice and eliminated through the alimentary canal.

Lungs

1. The lungs help in the elimination of carbon dioxide by expiration.
2. Carbon dioxide is produced mainly as a result of respiration.
3. It can prove toxic if its concentration increases in blood.

Skin

1. The skin contains glands that secrete sweat and sebaceous glands which secrete sebum.
2. It helps in the elimination of sodium chloride, lactic acid, urea, glucose, and water through sweat.
3. Lipids and waxes are removed as sebum.