How urine is removed from the blood and then eliminated body?

The process by which urine is removed from the blood and eliminated from the body is called urination or micturition. Here's a detailed explanation of the steps involved:

1. Filtration:

- The kidneys play a crucial role in urine formation. They contain millions of tiny filtering units called nephrons, which are responsible for removing waste products and excess water from the blood.

- Blood enters the kidneys through the renal arteries.

- Inside the nephrons, the renal corpuscles (consisting of the glomerulus and Bowman's capsule) filter the blood.

- The glomerulus, a network of tiny blood vessels, allows small molecules like water, ions, glucose, amino acids, and waste products (urea, creatinine, etc.) to pass through, while larger molecules like proteins and blood cells remain in the bloodstream.

2. Reabsorption:

- The filtrate formed in the Bowman's capsule moves through the renal tubules.

- As the filtrate passes through the tubules, essential substances like glucose, amino acids, vitamins, and water are selectively reabsorbed back into the bloodstream.

- This process ensures that the body retains vital nutrients and fluids.

3. Secretion:

- While reabsorption is occurring, additional waste products, such as excess ions (potassium, hydrogen ions) and drugs, are actively secreted into the tubules from the bloodstream.

- This helps maintain proper electrolyte balance and remove harmful substances from the body.

4. Concentration:

- The remaining filtrate, now concentrated with waste products, moves into the collecting ducts.

- The collecting ducts are located in the renal medulla, which contains a high concentration of salt.

- Water is further reabsorbed from the filtrate as it passes through the medulla, concentrating the urine and conserving water in the body.

5. Elimination:

- The urine, which is now a concentrated solution of waste products and excess water, flows through the ureters, which are tubes connecting the kidneys to the urinary bladder.

- The bladder stores urine until it reaches a certain volume, triggering the urge to urinate.

- The bladder muscles contract, and the urine is expelled from the body through the urethra, the tube leading from the bladder to the outside.

This entire process of urine formation and elimination is regulated by various hormones and neural mechanisms to maintain optimal fluid and electrolyte balance, remove waste products, and regulate blood pH.