Excretion is the body expelling waste substances that it does not need and that may cause it harm.
The excretory system consists of the urinary apparatus (formed by the urinary tract and the kidneys), the skin, the lungs and the liver.
The excretory system
Interactive activity that identifies and describes the main organs of the male and female excretory system
The urinary system
The urinary system is all of the organs that produce and excrete urine, the main waste liquid of the body. It consists of the urinary tracts and the kidneys.
Blood reaches the kidneys, where it is filtered and any substances that could be harmful to the body are removed. Human beings have two kidneys located in the lumbar region, at the bottom of the ribs, and they are shaped like beans. Inside, waste substances are extracted from the blood, which, dissolved in water, make up the urine.
Urine is a yellowish liquid consisting of water, mineral salts and substances that are toxic to the organism, which are the main waste substances that the kidneys remove from the blood.
The urinary tracts consist of the ureters, the bladder and the urethra. The male urethra is somewhat longer and serves as both a urinary and genital tract.Conversely, the female urethra is only a urinary tract and is independent of the genital tracts.
The excretory or urinary system
Animation that shows the parts and functions of the excretory or urinary system
The lungs and liver
The lungs, which are the central organs of the respiratory system, are responsible for removing carbon dioxide from the blood. Carbon dioxide is produced through cellular respiration and is toxic to our bodies.
The liver, an organ that forms part of the digestive system, removes toxic substances collected by the blood during digestion; they form part of the bile and are removed in the faeces.5.3
The skin is the largest organ of the human body. It forms part of the excretory system and, together with the urinary system, contributes to removing toxins.
The body expels some of the waste substances that it generates through the skin It does this through the sweat glands, which secrete a mixture of toxins and water calledsweat outside the body.
The skin consists of different tissues: the dermis, which is the location of different types of gland, such as the sweat glands, and the epidermis, which is the location of the pores through which sweat is released.
When we run, our body releases sweat, and with it, toxins. This is one reason why taking part in sport is such a healthy habit.
Sweat is a mixture of different substances (water, salt, urea, uric acid, etc.), and it performs the following functions:
- It helps to regulate body temperature by providing a cooling mechanism.This is why, when we do exercise, our bodies get warmer and sweat.
- It collaborates with the excretory function to remove toxic residues.
The process of excretion
The blood distributes nutrients throughout the body, but it also carries toxic residues that have to be removed to the organs responsible for excretion, such as the kidneys, lungs, liver and skin .
Blood arriving at the kidneys goes through a system of channels surrounded by a dense network of blood vessels, where some substances are reabsorbed into circulation and others are eliminated in the form of urine.
Urine = water + salts + toxic substances.
The urine coming from the kidneys flows through the ureters until it reaches thebladder. Urine exits through the urethra in urination and the bladder is left virtually empty.
At the same time, when the blood carries toxic residues to the liver, it processes them, empties them into the bile and eliminates them through the faeces.
Sweat produced by the sweat glands in the skin also helps us to eliminate toxic substances.
- What are kidneys?
- What kidneys do
- Looking after your kidneys
- When kidneys don’t work well
- Some interesting facts about kidneys
- Dr Kate says
Your kidneys are two of the most important organs in your body. They filter your blood and help get rid of waste products from your body.
Each kidney is about the size of a mobile phone. They have an unusual shape – kidney beans are named after them because they have the same shape.
They are found just under your back ribs, but you can’t feel them with your hands.
Here is a diagram of a kidney to help you understand how it all works.
Inside each kidney there are about a million nephrons (say nef-ronz). They are tiny filters catching all the stuff that your body doesn’t need and sending it out as waste.
The kidneys do several important jobs which help to keep your body working well.
- They get rid of waste products carried in the blood.
The kidneys are part of the waste disposal team. They check out the minerals, vitamins and other nutrients that you get from your food and send off into urine anything that is not needed. They make urine (wee), send it down to the bladder through tubes called the ureters, and when the bladder feels full enough the brain sends you off to the toilet to get rid of the urine. Have a look at ‘Your waste disposal system’ if you would like to know more about this.
- They balance the volume of fluid in the body.
Adults have around 7 to 8 litres of blood in their body (kids have a smaller amount, depending on how big they are). All of this gets filtered through the kidneys many times a day. If the volume of fluid in your body goes down (maybe you are sweating out a lot of fluid through your skin or maybe you are not drinking enough water), the kidneys will not make much urine until the amount of fluid in your body goes up.
- They can change blood pressure.
The kidneys make a hormone that can constrict (make narrower) the arteries in the body. This causes blood pressure to rise when a higher pressure is needed to make sure that blood gets to all parts of your body.
- They help in making red blood cells.
The kidneys make a hormone that tells the body when to make more red blood cells.
- They produce active vitamin D.
Vitamin D helps the body to absorb calcium from dairy products and some other foods that you eat. Calcium is needed to make strong bones and teeth.
You can look after your kidneys by:
- drinking 6 – 8 glasses of water or other drinks (such as milk drinks or fruit juice) each day. Your kidneys like water best.
- eating a healthy diet so that you get all the minerals and vitamins that your body needs
- not eating a lot of ‘sometimes’ treats. Our topic ‘Balanced diet’ can help you.
- staying away from drugs like tobacco and alcohol – these make the kidneys’ job more difficult.
Your body can still work quite well with only one kidney, so long as that kidney is healthy.
Some people don’t have healthy kidneys, and sometimes their kidneys stop working.
Some people need to go on a special machine that acts like a kidney to wash and clean the blood. This is calleddialysis (say di-a-li-siss). These machines are very expensive and it takes several hours a day for about 3 days a week. This makes it difficult for those people to live their lives.
Sometimes people may be lucky enough to have a dialysis machine at home.
Sometimes people can have a kidney transplant, which means that they get a kidney from some other person, often someone in the family, and special doctors at the hospital put it into their body.
Healthy kidneys stop red blood cells from going into urine. If you ever see blood in your wee, tell whoever looks after you.
Renal is a word that means ‘to do with the kidney’.
Kidney stones can form in the kidney.
Homeostasis (say hom-ee-oh-stay-sis) is what doctors call the work that the kidney does to balance your body’s fluids.
Want to see more about how kidneys work and check how much you know about kidneys? Click here
If your friend has kidney problems, maybe you can help by keeping her company sometimes when she is on dialysis. Kids who have any kinds of problems are still kids like you. They need friends, they need to have fun, they can do things, they can learn and they can be good friends too.
|Kidneys raise and lower blood pressure
I have healthy kidneys
Never smoke and drink plenty of water
Each kidney produces vitamin D
Your kidneys balance your fluid.
Toxins are expelled through the excretory system. The most important organs of the excretory system are the kidney, liver and skin. The liver works as a filter helping to catch wastes and remove them from the body. Excess salt is removed out of the body by the kidneys. The skin secretes salt, water and other toxins out of the body by sweating. The excretory system is very important for keeping the body clean.
- Your Urinary System and How it Works
- Your Kidneys
- Your Urinary System
- IMCPL Kids’ Info Guide: Excretory System
- Human Excretory System
- Excretory System
- Urinary System: Getting Rid of Waste
Excretion Is Not Elimination
The excretory system is very important to your body and only has a few parts. In a similar way to removing solid waste from your body, you must also get rid of fluids. You know the results of the excretory system as urine.
Urine is the result of the excretory system balancing the amount of water and salts in your body. We said the system is small. Your kidneys are the core organs involved in the excretory system. Related body parts include the ureters, bladder, and urethra. Once the urine passes through your urethra, that’s it, it’s out of your body.
What Does This System Do?
What do those kidneys do? The regulation process of body fluids and salt levels is also called osmoregulation. The kidneys act as a filter. Eventually all of the blood in your body passes through the kidneys and they are able to do their filtering magic. The kidneys pull harmful molecules out of your bloodstream and leave the ones that are good for you.
The kidneys are also key players in the hydration (water) levels for your body. Let’s say you are in the desert and you haven’t been drinking much water. Chemical signals are sent to your kidneys to reabsorb as much water as possible. The result is less urine creation and your body loses less water. A normal day has you creating about one and a half liters of fluid.
Interacting with Other Systems
The excretory system is a close partner with both the circulatory and endocrine system. The circulatory system connection is obvious. Blood that circulates through the body passes through one of the two kidneys. Urea, uric acid, and water are removed from the blood and most of the water is put back into the system.
The endocrine system is the major controller of the excretory system. As levels of compounds and fluids are monitored, kidney function must be constantly altered to provide the best internal environment for your cells. If you drink too much water, hormones are released that allow for more urine production. If you are dehydrated, less urine will be produced. The kidneys are also tied to the endocrine system with the adrenal gland position on the top of each kidney. The adrenals release adrenaline into your body.
While there are many diseases of the excretory system, even more problems can be created by a malfunctioning set of kidneys. Blood pressure is closely tied to the amount of fluid in your body. If a kidney does not work and filter properly, blood pressure can increase to dangerous levels. If that weren’t bad enough, urea would accumulate in your tissues and would slowly poison the cells of your body.
People with malfunctioning kidneys often have to go through a process called dialysis where they are hooked up to a machine that filters their blood. The machine acts as an artificial kidney and tries to re-establish normal levels of ions and water in their bodies. Many people on dialysis are waiting for kidney transplants.