The Excretory System

The process by which waste products are removed from the body is called excretion. The excretory system removes bodily waste as well as excess water from the body. The major organs which make up the excretory system include the kidneys, the bladder, the liver, the skin and the lungs. We will examine each one.

The Kidneys

The kidneys are a pair of organs found in your abdomen. They are shaped like beans and are about the size of your fist. All the blood in your body passes through your kidneys many times each day. The kidneys remove waste (such as urea) and excess water from the blood as it passes through them. This excess water and waste is known as urine. Each kidney has a tube attached to it which is called a ureter. Urine drains from the kidneys, through the ureters and into the bladder.

The Bladder

The bladder is a small muscular sac in which urine is collected and stored. Urine passes into the bladder from the two ureters. The urine is stored in the bladder until we are ready to get rid of it through a process called urination. When we urinate, urine passes out of the bladder, through a tube called the urethra and out of the body. The diagram below shows where the kidneys and bladder are located in the body.

 The Liver

The liver is a large, triangle shaped organ found in the abdomen (see diagram below). It performs many functions. As blood flows into the liver, some harmful substances (called toxins) are broken down and changed into other substances which will not harm the body. Other toxins are removed from the blood. The liver also produces bile which is stored in the gall bladder. Bile helps carry away waste products. Some waste products which are removed by the liver are excreted into the bile. Bile containing waste products travels to the intestines where it eventually passes out of the body in the feces.

The Skin

The skin is the largest organ. It covers the entire body. Some waste products are excreted through the skin through a process called perspiration. When we perspire (sweat), water and waste products such urea and ammonia pass out of the body through the skin. Sweat is secreted from sweat glands below the surface of the skin through tiny holes in the skin called pores (Take a look at the diagram below).

The Lungs

As the cells in our body perform their various functions, they produce a waste gas called carbon dioxide. This carbon dioxide is released into the blood and carried to the lungs. The carbon dioxide passes out of the body through a process called exhalation. Every time we exhale (breathe out), we are removing carbon dioxide from our bodies.

Note: Excretion should not be confused with egestion. Excretion refers to the removal of waste from the body. Egestion means passing out undigested material from the body at the end of the digestion process. It is important to know the difference.

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References

http://www.mcwdn.org/body/excretory.html

http://www.healthline.com/human-body-maps/liver

https://commons.wikimedia.org/wiki/File:Urinary_(male).jpg

https://commons.wikimedia.org/wiki/File:Anatomy_The_Skin_-_NCI_Visuals_Online.jpg

Blausen.com staff. “Blausen gallery 2014”. Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762.