Taking Out the Trash: How Excretory Organs Maintain Balance In Your Body

This is the first post in a two part series on the Excretory System. Read Part 2 (Dangerous Buildup: How Toxins Affect the Body).

I debated on whether or not to cover this system in this initial series of blog posts on Body Basics. The reason is that each of the organs involved in this system are explained in greater detail within another system. However, I think when we look at these organs as a group we can see a more accurate picture of how the systems are working together as a whole to take care of your body.

The organs that make up this system are the Kidneys, Liver, Large Intestine, Lungs and Skin. These organs all work to remove excess water and waste products from the body within the larger body system that they are connected to.

Kidneys

The kidneys play a detailed role as part of the Urinary System. These are also probably the first organs that came to mind when I mentioned the Excretory System. That is understandable as the main focus of this system is to eliminate excess water and waste products from the body.

Your renal artery delivers blood to your kidney. This artery branches into smaller segments until it reaches a nephron (there are about a million nephrons inside your kidney). This is where the waste removal process begins. Each nephron has two parts, a glomerulus and a renal tubule. When the artery enters the glomerulus it enters a network of capillaries. These capillaries keep the larger items like red blood cells and proteins inside your blood, while allowing smaller items to enter the glomerulus.

The glomerulus then sends these smaller items into a renal tubule. This is where the waste products in your blood gets filtered out. The tubule hangs onto things like urea and creatinine. Urea is a waste product left over by the liver after it breaks down proteins, it contains nitrogen and needs to get removed from your body. Creatinine is a waste product that is made by your muscles after the normal process of them using energy to help your body move. This renal tubule also hangs onto a portion of the acid that accumulates in your blood to prevent your blood from becoming too acidic which is very important for keeping your body functioning properly. All of these products that have been identified for removal are than sent down to your bladder to be excreted from your body next time you pee.

Liver

This is an organ of many functions. We see the liver in more detail within the Digestive System as it secretes bile that is essential for the breakdown of food within the small intestine and is then responsible for processing the nutrients that have been absorbed. Lets take a closer look at the role of the liver in excretion.

The Liver plays a role in cleaning out your blood, it cleans out products that are absorbed from outside of your body (think medications or alcohol) as well as cleaning out products produced within your body (think old red blood cells). The liver is the largest organ in your body and at any time there is about 1 pint of blood within it (considering that the average body holds 10 pints of blood this is a large amount!) The liver is a key player in breaking down old red blood cells. To do this the liver breaks the cell back down to it’s components of heme and globin so these products can be recycled by the body to create new red blood cells. During this process it created a substance called bilirubin that is excreted into the bile. Some drugs are eliminated through the liver in the form of bile. Other toxins that may have been absorbed by the small intestine or bacteria that have entered the blood are also filtered out. Amino Acids are a building block for proteins, however when proteins are broken down they produce a substance called ammonia which can be very harmful to the body. The liver is responsible for converting ammonia into urea so that it can be removed from the body by the kidneys. Whereas any product that the liver identifies as harmful and turns into bile is excreted by your poop.

Large Intestine

Other than your kidneys this was probably the second organ that came to mind when I mentioned the excretory system. Our poop is another large player in eliminating waste from our bodies. The Large Intestine is a more detailed part of your Digestive System and it’s main job is to make your poop. The large intestine holds onto all of the waste that has been passed into it from the other areas of the digestive tract and turns it into a mass that will leave your body in the form of your poop.

Lungs

Did you think of your lungs when I mentioned the Excretory System? Your lungs are actually playing an extremely important and continuous role of excretion for your body. Your body is made up of cells and as these cells use oxygen to work they create a waste product known as carbon dioxide. When your red blood cells deliver oxygen to a cell they also pick up it’s carbon dioxide waste. When the red blood cell gets back to the capillaries in the lungs it is full of carbon dioxide and it can’t receive any new oxygen. So as your blood travels through the capillaries in your air sac not only is it picking up oxygen but it is passing over its carbon dioxide waste.

Skin

This is another organ like our lungs that we may take for granted as being part of our body’s intricate process of elimination. While we are often acutely aware of the sweat our body is producing we may not be giving it credit for how useful that substance actually is! Within our sweat our body is excreting excess water and electrolytes (like sodium), as well as some urea. Pretty amazing!

While excretion may not be one of the prettiest conversations to have about our bodies it is an absolutely vital function for daily life. As soon as any of these organs stop doing their work of excretion waste begins to build up in our body. If this continues to accumulate there can be serious consequences leading to long term medical interventions like dialysis or worse complications such as our cells being unable to get rid of carbon dioxide.