Main Waste Products

Carbon Dioxide

• Produced during cellular respiration and dissolves to form carbolic acid which can change the pH of body fluids and affect enzyme activity
• Excreted via lungs in expired air

Urea

• Nitrogenous waste products (urea, uric acid, creatinine)
• Produced when excess dietary amino acids are deaminated in liver
• Excreted by kidneys in urine

Bile pigments

• Derived from breakdown of haemoglobin, takes place in liver
• Excreted by liver via intestines as faeces

Excess water

• Produced by respiring cells
• Excreted mainly via kidneys as urine, lungs as water vapour and skin as sweat

Removal of faeces is not regarded as excretion