Formation of Urine in the Human Body

Filtration:
- The process of urine formation begins in the kidneys where blood is filtered to remove waste products and excess substances.
- The blood enters the kidney through the renal artery and is filtered in the glomerulus, a network of capillaries.

Reabsorption:
- After filtration, the filtrate enters the renal tubules where reabsorption of essential substances like glucose, water, and ions occurs.
- Reabsorption ensures that important substances are not lost in the urine.

Secretion:
- In this stage, additional waste products and excess substances are actively transported from the blood into the filtrate.
- This helps in further removing harmful substances from the body.

Concentration:
- The filtrate, now called urine, moves through the collecting duct where water is reabsorbed based on the body's needs.
- This process helps in concentrating the urine by removing excess water.

Excretion:
- The concentrated urine is then passed from the kidneys to the bladder through the ureters.
- The bladder stores the urine until it is eliminated from the body through the urethra.
By following these steps of filtration, reabsorption, secretion, concentration, and excretion, the human body effectively forms and eliminates urine.