The excretory system is the set of organs in our body that is responsible for excretion, that is, the elimination of metabolic waste products to the outside. This system is made up of various organs of our body that perform excretory functions; Of these, the most recognized are the kidneys and the urinary system, but the lungs, skin and intestines also have important excretory functions. Every day our body needs to receive oxygen, nutrients and fluids to hydrate and feed the cells that make up its tissues and organs. However, not everything that is in food, liquids and air that enters our body is fully used, and what can not be used or what results from metabolism is what represents what is known as material . or waste product. The main waste produced in our body is urine, feces, sweat and the carbon dioxide (CO₂) that we exhale, which is actually the sum of the metabolic waste produced at the level of each of our cells as a result. of the processing of carbohydrates, proteins, lipids and fats, etc. The elimination of all these wastes is very important for our health, since many times these materials contain certain molecules that, if they accumulate, can make us feel bad or cause some diseases; it is the elimination of these molecules that the organs of excretion are in charge of. Today I will explain the functions of the excretory system, its parts and how it works. If you want to learn more about this or other topics, visit lifeder.com and search in the web search engine. Functions of the excretory system The excretory system has various functions and all are essential for the proper functioning of our body. Among some of them the following can be distinguished: - Eliminate excess fluids and with them toxins and some waste molecules that are extracted from the blood when it is "filtered" (urea, uric acid, ammonia, etc.). - Maintain the osmoregulation of our body, which is nothing more than the regulation of fluid and salt levels. - Prevent dehydration. - Eliminate medications, drugs or other substances that it receives from the body. - Regulate body temperature and excess electrolytes. - Get rid of solid waste resulting from the digestion of food, which represents all non- assimilable or non-absorbed materials from what we eat - Expel carbon dioxide from the body (produced during cellular respiration). Parts of the excretory system (organs) The excretory system is responsible for the excretion of waste products. These waste products are urine, feces, carbon dioxide, and sweat. Let's see: For the excretion of urine The kidneys are the main organs of excretion of the body. These are part of the urinary system and other structures/organs such as the ureters, the urinary bladder and the urethra participate in their functions. In our body there are two kidneys, which are the size of a fist and are located on each side of our spine, more or less at the same level as the liver (just below the diaphragm). These small organs are responsible for filtering the blood and producing some substances that regulate different internal aspects of our body (hormones). The products that are filtered from the blood are eliminated with the urine. The ureters are tubes that are responsible for directing urine from the kidneys to the urinary bladder, which is a “sack”-shaped organ where urine is stored until it is excreted outside the body when we urinate (a process called urination). The elimination of urine occurs through another tube called the urethra, which is connected to the urinary bladder at one end and to a sphincter (a valve) at the other. For the excretion of solids (faeces) The digestive system performs very special functions during the excretion of waste. In the intestines , everything that is not digested from food is eliminated as fecal matter. A couple of very important glandular organs participate in this system, which are responsible for excreting many substances into the intestines that facilitate the digestion of what we eat. These organs are the liver and the pancreas. For the excretion of CO₂ The respiratory system includes the organs that are responsible for the excretion of carbon dioxide (CO₂) produced by the respiration of our cells. Its function is dual: on the one hand, it allows oxygenated air to enter our body when we inhale, where oxygen is delivered to the blood. On the other hand, it receives from the blood the CO₂ that is produced by the cells during respiration and eliminates it when we exhale. For fluid excretion and temperature regulation The skin is the largest organ in our body. In addition to protecting everything we have inside and helping us perceive some sensations such as touch, cold and heat, this organ is responsible for the fundamental process of sweating. Sweating not only functions in the elimination of excess fluids, but also participates in the regulation of electrolyte balance and -the most important of all- of body temperature, especially in conditions of high temperatures, internal or external. These functions are possible thanks to the existence, under our skin, of small structures known as sweat glands. How does the excretory system work? Let's see in a little more detail how the excretory system of the kidneys works, which is responsible for the elimination of metabolic waste products through urine. 1- Cellular metabolism All the cells of our body constantly receive nutrients, which must be metabolized. Much of these nutrients are used to obtain energy, but waste is also produced that must be eliminated, since it can be harmful if it accumulates excessively. Tissue cells remove their waste into the space around them, which is known as the extracellular space. These wastes then reach the blood plasma and it is in the elimination of these wastes that the excretory system of the kidneys participates. Generally, these waste molecules are soluble in water, which is why it is used in our body, among other things, as a vehicle for the transport and elimination of cellular metabolic waste. 2- The blood and the kidneys All the blood in the body passes through the kidneys successive times during the day and the kidneys are perfectly designed to filter all the blood they receive: inside there are hundreds of small filtering structures called nephrons. The heart pumps blood to the kidneys through the renal arteries; When this blood reaches the kidneys, it is first conducted into the kidneys through small capillaries and then to the glomeruli, which are the filtering structures inside each nephron. In the glomeruli there is a lot of pressure, which allows a portion of the liquid to be extracted from the blood with the waste molecules. This liquid is known as filtrate and it is from this liquid that harmful molecules will be extracted and from which some molecules that should not be discarded in their passage through the rest of the kidney structure will be reabsorbed. 3- Reabsorption and concentration Although the kidneys are mainly responsible for filtering and eliminating the metabolic waste contained in the blood, they also participate in the process of reabsorbing water, salts, ions, proteins and carbohydrates found in the filtrate. Therefore, what is excreted is only a small percentage of everything that passes through the filtering structures of the kidney, which is also highly concentrated, since a large part of the water it contains is removed. 4- Formation of urine Through a fairly long and complicated process, the filtrate becomes urine and this is conducted through the ureters to the bladder, where it is stored until we "decide" to urinate, which implies that the bladder empty into the urethra and from there be expelled from our body.