How animals excrete

The main excretory products of animals are urea, salts, carbon dioxide gas and water.

Route	What leaves	Organ
Urine	Urea, water, salts	Kidneys
Exhaled air	CO₂ gas, H₂O	Lungs
Sweat	Water, salts	Skin

Figure to be added

Figure 8.11 — the different routes by which excretion happens in an organism: sweat, exhaled air and urine.

Animal bodies have organ systems arranged for excretion. In a human being the nitrogenous excretory process happens mainly through the kidneys.

Excretion, or just getting rid of?

Faeces are not an excretory product. They are not something produced by metabolism inside cells but undigested food left over — it never entered the body's cells at all. Urea is different: it is made in the liver by breaking protein down, so it is a genuine excretory product.