- Homeostasis is the physiological maintenance of its internal environment by an organism. - Review: Metabolism is the sum total of all catabolic (breakdown) and anabolic (synthesis) reactions in the body. - During metabolic processes, the body produces toxic wastes, such as carbonic acid and ammonia. Carbon dioxide, an end product of respiration, combines with water to form carbonic acid. Ammonia results from the metabolic removal of nitrogen from proteins and nucleic acids.

- In part, the action of the excretory organs maintains homeostasis. The excretory system’s major components are: - Skin. Skin is the largest organ of the human body. Because of the large number of sweat glands, skin is a primary excretory organ. Sweat glands perform two main functions: · removing water, salt, and urea · regulating temperature - Urea is a nitrogenous-waste product of the body. After it is secreted, urea is metabolized by bacteria and forms ammonia. The ammonia causes the odor associated with sweat.

- Lungs. The lungs excrete CO2 and H2O. The removal of CO2 helps to regulate the pH of the blood. CO2 combines with H2O to form carbonic acid, which can decrease the blood pH and potentially affect enzymatic reactions. - Liver. Among other functions, the liver is involved in protein recycling. In one part of the process, the amino group undergoes oxidative deamination and is liberated as ammonia. The ammonia combines with carbon dioxide to form urea. The circulatory system carries the urea from the liver to the kidneys.

- Urogenital system. The urogenital system filters, stores, and removes liquid waste, such as urine, from the body. Blood vessels carry urea to the kidneys. Urine (containing urea, salts, and other compounds) exits the kidney and drains into the bladder. Urine leaves the body through a tube called the urethra.

What is the function of the urea cycle?

- To convert NH2 from amino acids into urea.

- excrete salt. - excrete urea. - excrete water.

Excretion can be defined as

- the disposal of the by-products of metabolism from the body.

12.7.1 Human Excretion: Waste Processing Flashcards by Irina Soloshenko

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12.7.1 Human Excretion: Waste Processing Flashcards

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