The main nitrogenous waste formed in the human body is

1. Excretion and Osmoregulation:

(i) Excretion and osmoregulation are two essential processes to maintain constancy in the internal environment of our body.

(ii) The removal of metabolic wastes from the body is termed as excretion.

(iii) In higher vertebrates, kidneys perform both excretion and osmoregulation.

2. Various excretory organs:

(i) Other excretory organs in the human body except kidneys are skin, lungs, and liver.

(ii) The excretory system in the human body consists of kidneys, ureters, urinary bladder, and urethra.

3. Structure of Kidney:

(i) The primary functional units of kidneys are called nephrons, whose function is to filter blood and remove wastes.

(ii) The outermost part of a kidney is called the renal cortex, and the innermost part is called the renal medulla.

4. Structure of a nephron:

(i) Nephrons originate in the cortex region and extend into the medulla region.

(ii) A nephron consists of two parts such as Malpighian corpuscle and long coiled tubule.

(iii) The Malpighian corpuscle consists of the glomerulus and Bowman's capsule.

(iv) The long coiled tubule has three parts, such as proximal convoluted tubule, a loop of Henle, and distal convoluted tubule.

5. Formation of urine:

(i) Urine formation in nephron involves three basic steps: Ultrafiltration, Selective reabsorption, Tubular secretion.

(ii) The ADH (Antidiuretic hormone) plays an important role in the reabsorption of water from collecting tubules.

6. Composition of urine:

The urine is composed of urea (a primary constituent), ammonia, uric acid, creatinine, sodium chloride, sulphates, chlorides, phosphates, calcium, magnesium, etc.

7. Haemodialysis:

(i) Dialysis is a method of separating small molecules from large ones using a semipermeable membrane.

(ii) Blood dialysis or Haemodialysis separates smaller molecules like urea and other metabolic wastes from the blood while the large ones like proteins are retained in the plasma.