Overview About Kidneys

Kidneys don’t always get the respect they deserve. But, kidneys are truly impressive and the more you learn, the more you’ll understand why you want to help keep them healthy.

Another word for kidney is renal. You may hear your doctor talk about renal function or read materials that mention renal failure. Whenever you see or hear the word renal, you will know the subject is about kidneys.

Location and description

The kidneys are two bean-shaped organs about five-inches long, three-inches wide and one-inch thick located in your back on each side of your spine. Each kidney is about the size of a fist and weighs from four to six ounces. They are situated above your waist, with the left kidney a little higher and a little larger. The right kidney is a little lower and smaller to make room for the liver. The lower ribs protect your kidneys.

Inside the kidneys are nephrons. These are tiny units where the filtering of excess fluids and dissolved particles occurs. There are between 1 and 1.3 million nephrons in each kidney.

What kidneys do

Most people think their kidneys are just responsible for producing urine, but there’s a lot more to it. In addition to removing extra fluid and water from your body, kidneys:

  • Filter the blood
  • Balance fluid content in the body
  • Produce the enzyme renin that helps control blood pressure
  • Produce the hormone erythropoietin to help make red blood cells
  • Activate vitamin D to maintain healthy bones
  • Adjust levels of minerals and other chemicals to keep the body working properly

How kidneys do their jobs

The basic function of kidneys begins when you eat and drink. After the body takes the nutrients it needs, the extras become wastes. Some of the waste winds up in the blood and needs to be filtered out. The blood gets circulated through the body with every beat of the heart. It’s the job of the kidneys — with their millions of nephrons — to filter and clean out the blood and remove the extra fluids. The extra fluid and waste becomes urine and travels from the kidneys down the ureters to the bladder until eliminated through the urethra.

Removing waste is only one job of the kidneys. In addition to filtering, the kidneys monitor the levels of chemicals, salts and acids in the blood. Inside the nephrons are sensors that keep track of sodium, phosphorus, calcium and potassium. When levels are high, the kidneys signal to remove the excess from your blood for elimination.

Another important job of the kidneys is to monitor and regulate certain body functions. An enzyme called renin is secreted by the kidneys to control blood pressure. A hormone called erythropoietin tells the bone marrow to make red blood cells, and one called calcitriol helps to keep bones strong.

Inside the kidneys

Inside each kidney is approximately 1 million tiny filtering units called nephrons. Each nephron has a glomerulus and tubules. The glomerulus is a series of specialized capillary loops where water and small particles are filtered from the blood. The waste and extra fluids then travel through the tube-like structure of the tubules where several processes take place to turn those fluids into urine. The tubules lead to the collecting duct where the urine is drained into a funnel-shaped sac called the renal pelvis. Each kidney has a ureter that connects the renal pelvis to the bladder. The urine from the kidneys flows down the ureters into the bladder and is then passed out of the body through the urethra.

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