why removal of urine(nitrogenous waste) is not considered as egestion ? what is the difference b/w egestion and excretion ?
Egestion is the discharge or expulsion of undigested material (food) from the digestive tract via the anus in case of multicellular organisms. Excretion on the other hand is getting rid of waste formed from the chemical reaction of the body, such as in urine, sweat, etc.
Egestion refers solely to indigestible matter which is never absorbed into the cells - it should not be confused with excretion of the waste products of metabolism. Undigested food has never been used in the body cells; it has merely passed through the alimentary canal.