What Are the Kidneys and Urinary Tract?

The urinary tract is one of the systems that our bodies use to get rid of waste products. The kidneys are the part of the urinary tract that makes urine (pee). Urine has salts, toxins, and water that need to be filtered out of the blood. After the kidneys make urine, it leaves the body using the rest of the urinary tract as a pathway.

What Are the Parts of the Urinary Tract?

People usually have two kidneys, but can live a normal, healthy life with just one. The kidneys are under the ribcage in the back, one on each side. Each adult kidney is about the size of a fist.

Each kidney has an outer layer called the cortex, which contains filtering units. The center part of the kidney, the medulla (meh-DUH-luh), has fan-shaped structures called pyramids. These drain urine into cup-shaped tubes called calyxes (KAY-luh-seez).

From the calyxes, pee travels out of the kidneys through the ureters (YUR-uh-ters) to be stored in the bladder (a muscular sac in the lower belly). When a person urinates, the pee exits the bladder and goes out of the body through the urethra (yoo-REE-thruh), another tube-like structure. The male urethra ends at the tip of the penis; the female urethra ends just above the vaginal opening.

What Do the Kidneys Do?

Kidneys have many jobs, from filtering blood and making urine to keeping bones healthy and making a hormone that controls the production of red blood cells. The kidneys also help regulate blood pressure, the level of salts in the blood, and the acid-base balance (the pH) of the blood. All these jobs make the kidneys essential to keeping the body working as it should.

How Do the Kidneys and Urinary Tract Work?

Blood travels to each kidney through the renal artery. The artery enters the kidney at the hilus (HY-luss), the indentation in middle of the kidney that gives it its bean shape. The artery then branches so blood can get to the nephrons (NEH-fronz) — 1 million tiny filtering units in each kidney that remove the harmful substances from the blood.

Each of the nephrons contain a filter called the glomerulus (gluh-MER-yuh-lus). The fluid that is filtered out from the blood then travels down a tiny tube-like structure called a tubule (TOO-byool). The tubule adjusts the level of salts, water, and wastes that will leave the body in pee. Filtered blood leaves the kidney through the renal vein and flows back to the heart.

Pee leaves the kidneys and travels through the ureters to the bladder. The bladder expands as it fills. When the bladder is full, nerve endings in its wall send messages to the brain. When a person needs to pee, the bladder walls tighten and a ring-like muscle that guards the exit from the bladder to the urethra, called the sphincter (SFINK-tur), relaxes. This lets pee go into the urethra and out of the body.

What Can Help Keep the Kidneys and Urinary Tract Healthy?

To help keep your child's kidneys and urinary tract healthy:

  • Encourage plenty of exercise.
  • Offer a nutritious diet.
  • Help your child stay hydrated.
  • Teach your daughter to wipe from front to back after pooping so germs don't get into the urethra.
  • Avoid bubble baths, sitting in the tub after shampoo has been used, and scented soaps. These can irritate the urethra.
  • Your child should wear cotton underwear.
  • Kids should change out of wet bathing suits promptly.
  • Go for regular medical checkups.
  • Talk to the doctor before giving your child any supplements or herbal treatments.
  • Let the doctor know about any family history of kidney problems, diabetes, or high blood pressure.
  • Let the doctor know if your child has any swelling or puffiness, has pain with peeing, needs to pee often, has foamy urine or blood in the urine, or is constipated.
Back to Articles


Related Articles

Urinary Tract Infections (UTIs)

You probably don't think much about urinating, or peeing. But what if it starts to sting? Find out more in this article for kids.

Read More

Urinary Tract Infections

A urinary tract infection (UTI) is one of the most common reasons that teens visit a doctor. Learn about the symptoms of UTIs, how they're treated, and more in this article.

Read More

Glomerulonephritis

With glomerulonephritis, tiny filtering units in the kidneys stop working properly, causing problems like too much fluid in the body and swelling. Most of the time it can be treated. Find out more.

Read More

Your Urinary System

You pee every day, but what makes it happen? Find out in this article for kids about the urinary system.

Read More

Nephrotic Syndrome

Nephrotic syndrome happens when tiny filtering units in the kidneys stop working properly. This can cause weight gain and other symptoms. Most kids eventually outgrow it.

Read More

Vesicoureteral Reflux (VUR)

This problem with the urinary tract causes urine to flow backward from the bladder to the kidneys. Most cases can be treated effectively, and many kids outgrow the condition.

Read More

Glomerulonephritis

Glomerulonephritis happens when tiny filtering units in the kidneys stop working properly. Most cases get better on their own or with treatment.

Read More

Kidney Disease

Sometimes, the kidneys can't do their job properly. In teens, kidney disease is usually due to infections, structural issues, glomerulonephritis, or nephrotic syndrome.

Read More

Urine Test: Creatinine

Low levels of creatinine in the urine may point to a kidney disease, certain muscular and neuromuscular disorders, or an obstruction of the urinary tract.

Read More

Urine Test: Microalbumin-to-Creatinine Ratio

The microalbumin-to-creatinine ratio test is most commonly used to screen for kidney problems in teens with diabetes. It may also be used to monitor kidney function in kids and teens who have a kidney disease.

Read More

Renal Tubular Acidosis

This kidney problem causes acid levels in the blood to become too high, causing fatigue, muscle weakness, and other kidney problems. The condition is usually treatable.

Read More

Dialysis

Dialysis is a medical treatment that can take over the job of filtering the blood until a person's failing kidneys heal or are replaced with a kidney transplant. Find out more in this article for teens.

Read More

Kidney Diseases in Childhood

The kidneys play a critical role in health. When something goes wrong, it could indicate a kidney disease. What are kidney diseases, and how can they be treated?

Read More

Kidneys and Urinary Tract

The kidneys perform several functions that are essential to health, the most important of which are to filter blood and produce urine.

Read More

Recurrent Urinary Tract Infections and Related Conditions

Recurrent urinary tract infections can cause kidney damage if left untreated, especially in kids under age 6. Here's how to recognize the symptom of UTIs and get help for your child.

Read More

Urinary Tract Infections

Urinary tract infections (UTIs) are common in kids. They're easy to treat and usually clear up in a week or so.

Read More

When Your Child Has a Chronic Kidney Disease

Parents of kids who have a chronic kidney disease often worry about what might happen next, how their child feels, and what treatments are likely to be involved. Find answers here.

Read More

Your Kidneys

You need at least one kidney to live. Find out why in this article for kids.

Read More

Kidney Transplant

If the kidneys stop working, a person will need either dialysis or a transplant. Get the facts on kidney transplant in this article for teens.

Read More

When Your Child Needs a Kidney Transplant

If your child needs a kidney transplant, you're probably feeling lots of emotions. Fortunately, many kids who undergo kidney transplants go on to live normal, healthy lives.

Read More

Kidney Stones

Kidney stones mostly happen to adults, but sometimes kids and teens can get them. Find out what kidney stones are, how to treat them, and ways to help prevent them.

Read More

Kidney Stones

Kidney stones mostly happen to adults, but sometimes teens can get them. Find out what kidney stones are, how to treat them, and ways to help prevent them.

Read More

Ultrasound: Bladder

Doctors order bladder ultrasounds when there's a concern about bladder problems, such as difficulty urinating or daytime wetting.

Read More

Urine Test: Calcium

A urine calcium test can help monitor or determine the cause of kidney stones and other kidney diseases, or detect overactivity or underactivity in the parathyroid glands.

Read More

Urine Tests

Is your child having a urine culture or urinalysis performed? Find out why urine tests are performed, and what to expect when the doctor orders them.

Read More

Ultrasound: Renal (Kidneys, Ureters, Bladder)

A renal ultrasound makes images of your child's kidneys, ureters, and bladder. Doctors may order this test if they suspect kidney damage, cysts, tumors, kidney stones, or complications from urinary tract infections.

Read More

Urine Test: Protein

The urine protein test is most commonly used to screen for kidney disease and also can help monitor kidney function.

Read More

Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2019 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.

Search our entire site.