The body takes nutrients from food and changes them to energy. After the body has taken the food components that it needs, waste products are left behind in the bowel and in the blood. The kidney and urinary systems help the body to get rid of liquid waste called urea.
They also help to keep chemicals such as potassium and sodium and water in balance. Urea is produced when foods containing protein such as meat, poultry, and certain vegetables are broken down in the body. Urea is carried in the blood to the kidneys. This is where it is removed, along with water and other wastes in the form of urine. The kidneys have other important functions.
They control blood pressure and produce the hormone erythropoietin. This hormone controls red blood cell production in the bone marrow. The kidneys also control the acid-base balance and conserve fluids. Two kidneys. This pair of purplish-brown organs is located below the ribs toward the middle of the back. Their function is to:. The kidneys remove urea from the blood through tiny filtering units called nephrons. Each kidney contains over 1 million tiny structures called nephrons. Each nephron has a glomerulus , the site of blood filtration.
As blood flows through the glomerulus, blood pressure pushes water and solutes from the capillaries into the capsule through a filtration membrane. This glomerular filtration begins the urine formation process. Inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule through a specialized layer of cells. This layer, the filtration membrane , allows water and small solutes to pass but blocks blood cells and large proteins.
Those components remain in the bloodstream. The filtrate the fluid that has passed through the membrane flows from the glomerular capsule further into the nephron.
The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule.
As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.
Pee also is a way for your body to keep the right amount of water. Did you ever notice that if you drink a lot, you pee more and the pee is pale yellow? That's because your body is getting rid of extra water and your pee has more water in it than usual.
Let's talk more about how the kidneys filter blood. When blood goes through the kidneys, water and some of the other stuff that is in blood like protein, glucose, and other nutrients go back into the bloodstream, while the waste and excess stuff is taken out.
Urine is what is left behind. But what is it exactly? Once pee is produced, it travels from the kidney to the bladder, where it's stored until you need to go to the bathroom. The bladder expands as it fills; when it's full, nerve endings in the bladder wall send a message to the brain that you need to pee. When you're in the bathroom, ready to go, the bladder walls contract and the sphincter a ringlike muscle that guards the exit from the bladder to the urethra relaxes.
The urine then flows from the bladder and out of the body through the urethra. For boys, the urethra ends at the tip of the penis.
For girls, it's in front of the vaginal opening. You might not think much about peeing or your urinary tract, but here's how you can help keep everything flowing as it should:.
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