What is the excretory system?

25 Tháng Năm, 2018

What is the excretory system?

Your body produces wastes. Your excretory system gets rid of these wastes. This system is really serveral systems:

  • Solid waste from digestion: Remember this waste leaves through the end of the large intestine (digestive system).
  • Carbon dioxide from body cells: Remember, you exhale this waste from your lungs( respiratory system).
  • Liquid wastes from body cells: The urinary system gets rid of these wastes.

+ These wastes are carried in the blood from the liver to the kidneys. The kidneys are two bean-shaped organs that filter these wastes out of the blood.

+ The kidneys then produce urine. Urine is waste and water.

  • Sweat: Sweat is water, salts, and wastes. It leaves your body through your skin system.

How does your kidney work?


All your blood passes through your kidneys about 60 times a day! Your kidneys remove substances from the blood that your body no longer needs. They also return to the blood substances your body does need.
1. An artery brings blood into a kidney. The artery branches into capillaries. The capillaries bring blood to the nephrons. A nephron is the part of a kidney where waste materials are separated from useful materials in the blood.
2. Wastes from the blood move out from the capillaries into the nephron. The wastes flow through a collecting duct. Collecting ducts from all the nephrons join into the ureter. The ureter leads the waste (urine) out of the kidney.
3. At the nephron, useful substances that may have been removed from the blood pass back into the capillaries. These capillaries lead blood to a vein. The vein carries the cleaned blood out of the kidney.

How does your body get rid of liquid wastes?

Your urinary system is like a drainage system. Your kidney collects wastes from the blood and forms urine.
• A tube called a ureter leads the urine out of the kidney
• The ureter brings urine into the bladder. Urine collects in the bladder for several hours.
• When the bladder is holding a lot of urine, eventually it is released into the urethra. The urethra carries urine from the bladder to outside the body.

The Skin.

Liquid waste also leaves your body through the skin. Sweat is made up of water, salts, and other wastes. Follow what happens in the skin diagram.


• Blood in the capillaries carries wastes. The wastes collect in a sweat gland.
• Sweat from the gland is pushed upward. It reaches the surface through an opening, called a pore (PAWR). At the surface it collects as droplets.
• The sweat evaporates from the surface. That is, the liquid turns into a gas and goes into the air. As the liquid turns into gas, it takes heat away from the skin. As heat is removed, your skin cools down.

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