What is the Function of the Excretory System?

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  • Written By: CW Deziel
  • Edited By: E. E. Hubbard
  • Last Modified Date: 10 December 2018
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The function of the excretory system is to remove waste and harmful by-products of normal metabolic processes from the body. If these waste products accumulate, they interfere with the delicate balance of oxygen, water, and nutrients needed for normal cell development. The main by-product of cell metabolism, carbon dioxide, is expelled by respiration, but cellular metabolism also produces a host of salts, fats, and excess chemicals, including carbon, hydrogen, oxygen, and nitrogen. The excretory system filters out those that are harmful and eliminates them so the body can maintain a state of homeostasis.

While the entire body is involved in the process of eliminating waste, the main organs of the excretory system are the kidneys. They are two bean-shaped organs located in the lower back that contain more than a million filtering units called nephrons. As blood passes through the kidneys, the nephrons filter out urea, a nitrogenous carbon compound produced by cell metabolism, and send it through tubes called ureters to the bladder where it is eliminated by urination. If the excretory system is functioning normal, the nephrons recycle beneficial substances, like glucose and proteins, back into the blood stream.


Elimination of waste from digestion is also a function of the excretory system, and the liver plays a role by decomposing worn out blood cells into bile pigments and passing them to the alimentary canal where they can be eliminated by defecation. The liver also produces urea and detoxifies the body by eliminating cholesterol and harmful toxins. The skin plays a role in maintaining a healthy internal balance by eliminating salts and other water soluble contaminants through perspiration. It is not considered part of the excretory system per se, because the process is more one of secretion than it is of active excretion.

Since the function of the excretory system is vital to maintaining health, kidney disease, or renal failure, is life-threatening. Symptoms include changes in urination, swelling in the legs, shortness of breath, fatigue, and skin rashes. If one kidney becomes diseased, it is possible for the body to function normally if the other is healthy. If both fail, a patient must rely on survival dialysis, which is external cleansing of the blood, unless a transplant can be performed. The liver's role in the excretory system is also vital, and, though it is a resilient organ, patients with acute liver failure suffer a high mortality rate.


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Post 7

@saraq90 - I can actually answer that reference without even seeing the movie because somewhere along the line I picked up a tidbit of information about diabetes being connected to kidney failure, something around the ballpark of forty percent of new cases of kidney failure are in diabetic patients.

However, I have also seen Steel Magnolias (fantastic movie - lots of quotable lines like "The only thing that separates us from the animals is our ability to accessorize.").

So I can tell you that the main character that has diabetes also ends up having kidney issues... I can't say any more than that - it might ruin the movie!

Post 6

@amysamp - I am missing your Steel Magnolias reference. I have seen parts of the movie and saw that the main character had diabetes, but am not seeing the connection to that and seeing the importance of the kidneys from diabetes...

Post 5

It sounds like the kidneys carry out major functions of the excretory system.

When I was playing soccer I had a teammate go into the hospital for quite some time and he suffered serious damage to one of his kidneys because of a hit he took to his lower back on the left side.

At that time I had confused the kidney as one of the organs like the appendix I did not understand the gravity of the situation. But now I get the function of the kidneys in the excretory system in that they are the filters of waste - that without them there is no waste leaving via urination.

Also there is no glucose and protein being filtered out and into our bloodstream.

I missed out completely on this importance - I should have known better since I had seen Steel Magnolias!

Post 4

@kentuckycat - The excretory system seems to be the system that incurs the most problems. The excretory system exits the waste and if the waste cannot exit then it stays inside and that is a major problem. Also, without organs like the kidneys it is impossible for the body to function and someone can incur massive pain. Simple problems processing waste can result in very painful experiences and may require seeing a doctor, even though some people see it as something very embarrassing to visit a doctor about.

Post 3

The human excretory system seems to be the system that people tend to take for granted. Since the respiratory system gathers much needed oxygen for the body to function and the digestive system processes the food and drinks that are consumed, they are seen as systems that have a very positive function for the human body.

The human excretory system serves as important a purpose as the others, but just due to the fact that it is releasing all the waste of the body it is not seen by some people as being as important as the others or its importance is taken for granted. I think that it may just be the specific purpose that the system serves, in that it expels "the bad" and does not take in any good.

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