Describe the role of liver, lungs and skin in excretion?

Question:

Describe the role of liver, lungs and skin in excretion?

Answer:

Liver: Converts ammonia to urea, removes bilirubin and some drugs into bile.
Lungs: Remove CO₂ and water vapour.
Skin: Sweat glands excrete water, salts and small amounts of urea.