This system of the human body is responsible for expelling unhelpful substances.
In this article we will talk about one of them: the excretory system, responsible for expelling substances that are not beneficial or toxic to the body. We will know what it consists of, what organs make it up, its characteristics and functions, its parts and the processes in which it intervenes.
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Excretory system: what is it?
The excretory system is one of the systems of the human body, andis responsible for eliminating substances that our body does not needonce it has taken advantage of the nutrients they have provided. This system is of great importance for the body, since it allows the elimination of toxins and waste and, by extension, the proper functioning of the body.
Waste removal occurs mainly through three routes: urination (expulsion of urine), respiration (absorption of oxygen and expulsion of carbon dioxide) and sweating (elimination of toxins through the skin).
Parts
The excretory system is made up of four organs or structures: the urinary system (formed, in turn, by four structures that we will see below), the skin, lungs and liver.
Let’s see in detail the four organs that make up the excretory system below, knowing their anatomy and functions.
1. Urinary system
The urinary system (also called generically “excretory system”) is made up of the following structures: the kidneys, ureters, bladder and urethra. The urinary system has a dual function: to produce and excrete urine. Urine is basically made up of water, although it also contains traces of other substances, such as urea (a toxic substance).
Urine is produced in the kidneys, and once formed, it descends from the kidneys to the bladder through tubes called ureters (there are two, one for each kidney).
Once in the bladder, the urine accumulates until the person feels the need to urinate (this need arises as a result of a series of nerve impulses, which detect that the bladder is beginning to fill). A curious fact is that although the bladder has a storage capacity of up to a liter, the need to urinate begins to be felt when about 400 or 500 cubic centimeters of urine accumulate.
Another interesting fact is that urine cannot go back to the kidneys once it is in the bladder; This happens because the bladder contains a series of valves that block the access of urine to the ureters.
We are going to see what each of these aforementioned structures that make up the urinary system consist of.
1.1. Kidneys
The kidneys are the main organ of the excretory system. These are two bean-shaped structures, weighing about 150 grams and measuring about 12 centimeters long and about 5 centimeters wide. These organs are located below the rib cage, where the ribs are located. We have two, each located on one side of the spine.
The basic function of the kidneys is to filter the blood and eliminate residues or waste from it, producing urine. In addition, it also filters the excess water that we consume.
1.2. ureters
The ureters, like the kidneys, are two. These are a kind of thin excretory ducts or “tubes” , each of which descends from the kidneys to the bladder, where urine is stored.
These ducts are approximately 30 centimeters long, and have a diameter of 0.5 centimeters. The walls of the ureters are thick and internally lined with mucosa.
Urine descends through the ureters through a series of peristaltic waves, which are contractions of the muscles of the digestive and excretory systems.
1.3. Urinary bladder
The urinary bladder is the structure responsible for storing urine before it is expelled through the urethra . Its storage capacity varies from one person to another, but it usually ranges between 500 cubic centimeters and a liter of urine.
1.4. Urethra
The urethra is the structure that allows urine to pass out of the body ; that is, it allows the process called “urination” (in ordinary language: “to pee” or “to pee”).
Anatomically, the urethra consists of a small tube-shaped duct. It has two sphincters at the beginning that allow control of the passage of urine. These sphincters, when we are born and we are small, are involuntary, but progressively they end up being voluntary; thus, sphincter control is usually acquired between the second and fourth year of life.
On the other hand, it is worth mentioning that in men, the urethra, in addition to fulfilling an excretory function, also has a reproductive function.
2. Skin
The skin is another of the organs of the excretory system, which allows the elimination of toxins, water, organic substances and salts , in addition to fulfilling other functions. It is the largest organ in the human body.
In the skin are located the sweat glands, responsible for secreting sweat, a transparent liquid composed of water, minerals, urea and lactic acid. The pores of the skin are responsible for expelling this sweat.
Thus, sweating is the process that allows, in addition to expelling toxins, to regulate our body temperature. We sweat when we do physical exercise, when we are nervous, when we are very hot, when we are overweight or when we eat spicy foods.
Types of sweat glands
Specifically, we find two types of sweat glands: eccrine and apocrine. While the former are found almost everywhere in the body and open on the surface of the skin, the latter are only found in areas where hair follicles abound (scalp, armpits, groin …), as they open in them.
3. Lungs
The lungs, although they are part of the respiratory system, are also considered part of the excretory system, since they are the organs responsible for expelling carbon dioxide (CO2) and therefore eliminating harmful substances.
Specifically, the lungs receive through the blood the cellular waste that the body needs to eliminate, and that have not been eliminated by the two previous organs (neither the kidneys nor the skin).
Through the process of respiration, water is released from the body, and this, in turn, obtains oxygen.
4. Liver
The liver is another organ of the excretory system, responsible for eliminating toxins and lipids, which are insoluble organic substances (fats). It is located in the upper right part of the abdomen.
In addition, the liver transforms ammonia (highly poisonous substance) into urea (less toxic substance), which passes into the blood and is excreted in the kidneys. As we have seen, harmful or unusable substances are excreted in the kidneys by the body.
On the other hand, another function that the liver fulfills is to break down hemoglobin from dead red blood cells in order to be used again.
Functions
Thus, as we have seen throughout the article, by way of synthesis, the main functions of the excretory system are basically the elimination of waste or toxic substances and the regulation of the balance of body fluids.
As we have seen, the excretory system is of vital importance for the body, since it eliminates those toxic substances, as well as wastes and waste that our body does not need and that, if accumulated, could cause problems (for example kidney stones). That is, it has an important “purifying” role.
The incorrect functioning of the excretory system translates into problems of renal failure, cystitis or nephritis, among others.
Another function of the excretory system isto regulate water levels and body fluids, facilitating homeostasis and osmoregulation.
References
- Latarjet, M., Ruiz, A., Pro, E. (2019). Human anatomy. Pan American Medical Publishing House.
- Megias , M. , Molist , P. , Pombal , MA (2019). Atlas of Plant and Animal Histology Animal organs: excretory. Atlas of the University of Vigo.
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