Role of other organs in excretion

Besides the kidneys, the lungs, liver and skin also help eliminate excretory wastes.

The lungs remove large amounts of CO₂, approximately 200 mL a minute, and a significant amount of water every day.

The liver, the largest gland in the body, secretes bile. Bile carries bilirubin, biliverdin, cholesterol, broken-down steroid hormones, vitamins and drugs, and most of these finally leave the body with the digestive wastes.

Sweat is a watery fluid holding NaCl, a little urea, lactic acid and other substances. Its main job is to cool the body surface, but it also removes some of these wastes.

Sebaceous glands give out sterols, hydrocarbons and waxes in sebum, which forms a protective oily covering over the skin.

Small amounts of nitrogenous wastes can be eliminated through saliva as well.