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11.37: Urinary System

Difficulty Level: At Grade Created by: CK-12
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Why is urine important?

You might have had to give a urine sample when you've gone to the doctor for a check-up. Urine is basically your liquid waste. The contents of your urine can tell the doctor if you have certain illnesses.

The Urinary System

Sometimes, the urinary system (Figure below) is called the excretory system. But the urinary system is only one part of the excretory system. Recall that the excretory system is also made up of the skin, lungs, and large intestine, as well as the kidneys. The urinary system is the organ system that makes, stores, and gets rid of urine.

Kidneys help filter blood and remove waste from your body

The kidneys filter the blood that passes through them, and the urinary bladder stores the urine until it is released from the body.

Organs of the Urinary System

  1. As you can see above (Figure above), the kidneys are two bean-shaped organs. Kidneys filter and clean the blood and form urine. They are about the size of your fists and are found near the middle of the back, just below your ribcage.
  2. Ureters are tube-shaped and bring urine from the kidneys to the urinary bladder.
  3. The urinary bladder is a hollow and muscular organ. It is shaped a little like a balloon. It is the organ that collects urine.
  4. Urine leaves the body through the urethra.

What is Urine?

Urine is a liquid that is formed by the kidneys when they filter wastes from the blood. Urine contains mostly water, but it also contains salts and nitrogen-containing molecules. The amount of urine released from the body depends on many things. Some of these include the amount of fluid and food a person consumes and how much fluid they have lost from sweating and breathing. Urine ranges from colorless to dark yellow but is usually a pale yellow color. Light yellow urine contains mostly water. The darker the urine, the less water it contains.

The urinary system also removes a type of waste called urea from your blood. Urea is a nitrogen-containing molecule that is made when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea and other wastes are carried in the bloodstream to the kidneys, where they are removed and form urine.


  • The urinary system is made up of the kidneys, the ureters, the bladder, and the urethra.
  • Urine is the liquid that is formed by the kidneys when they filter wastes from the blood. Urine contains water, salts, and nitrogen-containing molecules.

Explore More

Use the resource below to answer the questions that follow.

  1. What are three components of the renal system? Which part of this system is the main excretory organ of the body?
  2. What are three functions of the kidney?
  3. What capsule surrounds the glomerulus? How many of the capsules are found in the entire kidney?


  1. What is the urinary system?
  2. What is the main organ of the urinary system? What is the function of this organ?
  3. What is the difference between the urinary system and the excretory system?
  4. What is the purpose of the urinary bladder?

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kidneys Main organ of the excretory system; filters blood and forms urine.
urea Nitrogen-containing molecule made when foods containing protein are broken down in the body.
ureters Tube-like organs of the urinary system that move urine from the kidneys to the bladder.
urethra Tube-like organ of the urinary system that carries urine out of the body from the bladder; in males, it also carries sperm out of the body.
urinary bladder Hollow, balloon-shaped organ that stores urine.
urinary system Organ system that makes, stores, and gets rid of urine.
urine Liquid waste that is formed by the kidneys when they filter wastes from the blood.

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Difficulty Level:
At Grade
7 , 8
Date Created:
Nov 29, 2012
Last Modified:
Aug 30, 2016
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