Excretion is the vital biological process through which an organism expels waste products and harmful substances from its body, safeguarding its internal environment by maintaining homeostasis and preventing the accumulation of potentially harmful compounds.

Excretion involves the removal of metabolic wastes resulting from cellular activities such as Respiration, Digestion and Cellular metabolism. 

These waste products include 

Excretory products include a diverse array of substances which requires elimination from an organism’s body to maintain proper functioning. These include:

• Metabolic by-products resulting from internal chemical reactions of body 
• Excess water and ions derived from dietary intake.
• Hormones that have fulfilled their physiological roles and are non-reusable.
• Foreign substances, such as drugs, ingested through the alimentary canal and absorbed into the bloodstream.

Numerous chemical reactions occur within an organism’s cells to sustain life. Some of these reactions produce harmful by-products that must be eliminated. For instance, the breakdown of glucose during aerobic respiration yields carbon dioxide, which is transported by the blood to the lungs for removal. 

• Excess amino acids undergo deamination in the liver, producing glycogen and urea, which is transported by the blood to the kidneys for excretion.
• Urea and similar nitrogenous waste products, derived from protein breakdown, are promptly eliminated to prevent harmful accumulation.
• During feeding, surplus water and ions exceed the body’s requirements, necessitating expulsion to maintain balance.
• Hormones, crucial for bodily regulation, undergo metabolic changes in the liver before being excreted by the kidneys.
• The kidneys serve a central role in excretion, eliminating nitrogenous wastes, excess ions, and spent hormones via urine.

Excretory Organs