Urine is made in the kidneys when they filter waste products from the blood, but how exactly do they do it?  The urinary system is designed to remove certain waste materials from the body, including urea, excess ions and water. These waste materials are eliminated as urine which consists of the ions and urea dissolved in the excess water. The production of urine takes place in the kidneys. Here millions of microscopic filtering units, called nephrons, filter the blood and reabsorb important molecules such as glucose. Water and ions are also reabsorbed as required by the body. After it has... Show more

Urine is made in the kidneys when they filter waste products from the blood, but how exactly do they do it? 

The urinary system is designed to remove certain waste materials from the body, including urea, excess ions and water. These waste materials are eliminated as urine which consists of the ions and urea dissolved in the excess water. The production of urine takes place in the kidneys. Here millions of microscopic filtering units, called nephrons, filter the blood and reabsorb important molecules such as glucose. Water and ions are also reabsorbed as required by the body.

After it has been produced in the kidneys, the urine enters the ureter. One ureter leads from each of the kidneys and these take the urine to the bladder where it is stored and periodically eliminated from the body through the urethra. Blood is taken into the kidneys via the renal artery and removed after cleaning - the adjective renal refers to the kidneys so if you see something like renal damage written down, you know it means damage to a kidney.

Nephrons comprise the glomerulus, the Bowman's capsule, the convoluted tubules and the loop of Henle. The glomerulus first filters the blood. The glomerular filtrate contains water, urea, glucose and salts dissolved in water. Urea is a waste product from the breakdown of proteins in the liver. This filtrate is then collected by the Bowman's capsule and directed into the tubules where all of the useful materials, including all of the glucose, are reabsorbed. The loop of Henle is where osmoregulation occurs, ensuring thet the blood has the correct concentration of water. What is left is known as urine and it reaches the ureter via a collecting duct for transport to the bladder.

Kidneys are bean shaped organs that are situated just below the ribcage either side of the spine. If one fails, it is possible for the other to do the job of both. People suffering from complete kidney failure can be treated by dialysis or a kidney transplant. The dialysis machine takes over the job of detoxifying the blood and regulating the concentration of the blood plasma. Kidney failure patients who have a transplant often have to wait many months or even years before a suitable organ is found. The antigens of the donor need to be as close as possible to those of the patient to reduce the chances of tissue rejection.

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