Efficient excretory process as an integral part of metabolism - is an important condition for maintaining the homeostasis. It provides a body diseng

Excretory system organs (kidney, lungs, sweat and sebaceous glands, gastrointestinal tract, liver)

Efficient excretory process as an integral part of metabolism — is an important condition for maintaining the homeostasis. It provides a body disengagement from unnecessary and harmful products of metabolism, as well as foreign and toxic substances (alcohol, drugs, medicines, etc.), which came from the outside. Excretory organs are kidneys, lungs, skin (its sweat glands), salivary glands, gastrointestinal tract, and liver (diagram 96).

All physiological systems that perform excretory function constantly interact with each other. For example, for maintaining optimal body temperature in hot weather or heavy exertions, from the skin surface with sweat evaporates large amounts of water, release of which is significantly reduced with urine. And vice versa, at low temperature, when the evaporation of water through the skin is reduced, kidneys excrete more water.


Lungs excrete carbon dioxide, water vapor, and some volatile material (ether after anesthesia, alcohol). The volume of water vapor that is excreted with lungs, depend on the temperature and humidity of the environment, the level of physical and emotional stress.

Salivary and sweat glands

Salivary glands excrete drugs (e.g. aspirin), various foreign organic compounds that entered the body.

Sweat glands derive excess water, mineral salts, heavy metals, which can enter the body through food, some protein metabolism products (e.g. urea), during heavy physical work — even lactic acid.


An important excretory function is performed by the liver. Harmful substances that accidentally got with food in the intestine, as well as products of decay are absorbed from there into the blood and come to the liver. In it, they are neutralized, and lose their toxicity, and in composition of bile output from the intestine, which also frees the body from unnecessary and harmful products of metabolism, undigested food debris and pathogens. Taken from http://worldofschool.org

Diagram 96. Excretory system organs: 1 — salivary gland; 2 — lungs; 3 — kidney; 4 — the skin; 5 — liver; 6 — stomach, intestines


Kidneys — is the main organ of excretion in the human body. They perform two main functions — excretion of toxic products of protein metabolism and nucleic acid metabolism; maintain normal fluid and electrolyte composition of body fluids (blood, lymph, interstitial fluid). Furthermore, toxic and foreign substances excrete through the kidneys.

During splitting, in the cells of the nucleic and amino acids, produces ammonia, which is poisonous for the human body. Entering the bloodstream to the liver, it turns into a less toxic substance — urea, which eliminates through the kidneys in aqueous solution. This process is closely related to the exchange of water and salts in the body. Each day urine removes from the human body about 2 liters of water with dissolved therein urea, sodium chloride and small amounts of other substances.

  • Explain the biological significance of excretion system organs.

  • What organs perform excretory function?