The human body has 11 organ systems that work in tandem.
Among them, the removal of waste from the body is done primarily through
- Urinary system (liquid waste)
- Respiratory system (gaseous waste)
Also, partially supported by other systems, like
- Digestive system (solid waste by the liver)
- Circulatory system. (transporting the waste)
- Integumentary system (skin). (through sweat)
Of the above-mentioned four, there are a few organs that are specifically meant for waste removal, like the kidneys, liver, and skin.
However, unlike others, kidneys are the only vital organs that are specifically involved in the excretion process.
While other organs that remove waste from the body are also involved in other major functions.
What System Removes Waste from the Body
Urinary system
- The urinary system is the one that removes waste from the blood circulation.
- It cannot remove the waste material that is outside the reach of blood circulation.
All the waste material sorted out from the blood in the nephrons of the kidney is passed out as urine.
- See details on the kidney and its function.
How does it do
- The urinary system comprises of kidneys, ureters, urinary bladder, and urethra.
- Inside the kidneys, there are millions of nephrons that are involved in the filtration of blood from waste matter.
- Blood flows into the glomerulus of the nephron, and here, most of the matter from the blood gets filtered into the nephron.
- Here, the waste matter is retained, and the essential matter is reabsorbed into the blood.
- Even some of the matter that escapes filtration also gets secreted in the loop of nephrons.
- Thereby, most waste matter from the blood is filtered out into the nephron, which is expelled as urine.
- From the nephron, the urine formed enters the ureters, which pass into the urinary bladder.
- Here in the urinary bladder, it is stored temporarily and expelled through the urethra.
Digestive system
- This portion of the body that starts from the mouth and ends with the anus.
- It is a big tube-like structure that travels all along the body.
- It has many associated organs like the salivary glands, the liver, which expels the waste into the digestive tract.
- Besides, the undigested and unwanted matter in the food is also expelled.
- The liver is a key excretory organ of the digestive system. It is also a major organ for metabolism.
- Here, the complex molecules are broken down into simpler forms for expulsion from the body.
👉 The water-insoluble molecules are converted into water-soluble forms.
👉 The water-soluble metabolites are expelled through urine.
Whereas certain biomolecules, like the globin part of hemoglobin and other drug molecules, are directly expelled into the intestine.
- These expelled waste materials are carried out of the body through feces.
- So, the liver is involved in expulsion through both urine and feces.
- Salivary glands are also the organs involved in the expulsion of certain waste molecules.
👉 For example, the metabolite of phenytoin, an anticonvulsant drug, is expelled through saliva. This is carried away through feces.
Respiratory system
- The respiratory system is another body system that helps in the expulsion of waste in the form of gases from the body.
- When alcohol is consumed, the breath is filled with its odor. This is because alcohol is expelled through the lungs.
Circulatory system.
- This system comprises blood, blood vessels, and the heart.
- This system’s main role is to transport substances across the body.
- In doing so, they carry away the waste from remote parts of the body to the respective excretory organs like the kidney, liver, skin, etc.
Integumentary system.
- This system includes skin, hair, nails, and exocrine glands.
- Of them, the skin is the most prominent organ involved in waste removal from the body.
- When the blood carries waste material towards the skin. Some of the waste, like salts, urea, ammonia, and water, is expelled in sweat through skin pores.
We will see them in more detail on how they work to remove the waste from the body.
The following organs constitute the excretory system:
All the above organs are involved in elimination.
Elimination involves the removal of waste from the body.
Kidneys:
- These organs are located on the dorsal side of the body.
- Their main role is the purification of the blood.
- All the blood flows through the nephrons in the kidneys.
- During this flow, most of the waste is removed from the blood into the nephron tube.
- This waste is expelled as urine. Most drugs, electrolytes, uric acid, urea, etc., are expelled from the body.
- When blood flows into the kidneys, it reaches the nephrons.
- There, it undergoes processes like glomerular filtration, active tubular secretion, and passive tubular reabsorption. The waste formed is expelled in urine.
Skin:
- Skin is one of the minor organs of excretion.
- It helps to remove the waste in the form of sweat.
- It especially helps in the excretion of sodium chloride, urea, and aromatic substances like spices.
- During high temperatures, the body tries to regulate the internal heat by the expulsion of sweat.
- Hence, sweating is a natural physiological process to regulate body temperature.
- If we tried to avoid sweating by using an air-conditioned room or other cooling methods, the burden of waste removal lies on the kidneys.
- So, filtration and elimination increase the load on the kidneys, which leads to their damage in the long run.
- Even in the case of poisoning, the blood is decontaminated by the expulsion of toxins through urine.
Hence, the toxin elimination is hastened by either alkalinization or acidification of the urine.
Lungs:
- These are also the organs through which waste is removed in the form of gases.
- Lungs readily eliminate lipid-soluble compounds faster by breathing.
- They help in the expulsion of carbon dioxide, ammonia, ethyl alcohol, etc.
- So, we can identify if a person has consumed alcohol.
- Since ethanol is expelled from the lungs, we can quickly determine if the person is drunk.
Liver:
- It is another major organ of excretion.
- It metabolizes an insoluble substance, biological molecules like hormones, enzymes, etc.
- The water-insoluble forms are converted to water-soluble forms.
- These are then released into the blood for expulsion through the kidneys or into the intestine for expulsion through feces.
All the food and drugs we take enter the liver from the intestine.
Here, they undergo first-pass metabolism, which could lead to the elimination of toxins and waste.
Also, the waste in blood is partially expelled by the liver into the gut for expulsion.
Intestine: As such, the intestine is not involved in the excretion mechanism. However, the intestine helps to eliminate waste by not absorbing it back into the blood.
Besides the above, saliva and tears are also involved in excretion. Hence, you might have heard that teeth are damaged in a few patients due to drug treatment. These drugs are released into saliva, which degrades the teeth.