Question

What is the main nitrogenous waste in human beings?

Answer 1

The nature of the nitrogen containing wastes and their excretion varies among the species depending on the availability of water. Animals mostly excrete excess nitrogen as ammonia, urea or uric acid produced during protein metabolism. The animal body can store carbohydrates and fats for future use, but cannot store proteins or amino acids. Therefore, the amino acids which the body cannot use immediately are removed. The remaining organic acids are used as an energy source or changed to carbohydrate and then stored.

Complete answer:
The process by which nitrogen containing waste products of metabolism are eliminated from the body is called excretion.
The main nitrogenous waste in human beings is Urea is termed as ureotelism and the animals which excrete urea are known as ureotelic animals. Urea is produced as a waste by the decomposition of unused proteins in the liver. Our body must get rid of these waste materials because their accumulation in the body is poisonous and harms us. Our kidneys excrete urea, waste salts and excess water from the blood in the form of urine (a yellowish liquid).
Kidney helps in filtering our blood. Ureters are the tubes which carry urine to the bladder through the kidneys. The bladder is a type of bag which stores urine and the urethra is like a tube. The urine collected in the bladder (bag-like structure) is passed out from the body through a tube-like structure (urethra).

Note:
There are many disorders of the excretory system - Diabetes Insipidus, Uremia, Kidney Stones, Cystitis, etc.
There are sometimes various abnormal substances that are present in urine –
Proteinuria – presence of proteins.
Glycosuria – occurrence of glucose.
Haematuria – loss of blood.
Ketonuria – excretion of ketone bodies.
Pyuria – passing pus.