Excretion is the removal from the body of toxins formed as a result of metabolism. This process is a necessary condition for maintaining the constancy of its internal environment - homeostasis. The names of the excretory organs of animals are varied - specialized tubules, metanephridia. A person has a whole mechanism for this process.
Excretory Organ System
Exchange processes are quite complex and occur at all levels - from molecular to organismic. Therefore, a whole system is needed for their implementation. Human excretory organs excrete various substances.
Excess water is removed from the body through the lungs, skin, intestines and kidneys. Heavy metal s alts secrete the liver and intestines.
Lungs are respiratory organs, the essence of which is the intake of oxygen into the body and the removal of carbon dioxide from it. This process is of global importance. After all, plants use the carbon dioxide emitted by animals for photosynthesis. In the presence ofcarbon dioxide, water and light in the green parts of the plant, which contain the pigment chlorophyll, they form carbohydrate glucose and oxygen. This is such a vital circulation of substances in nature. Excess water is also continuously removed through the lungs.
The intestines bring out undigested food residues, and with them harmful metabolic products that can cause poisoning of the body.
Digestive gland liver - a real filter for the human body. It removes toxic substances from the blood. The liver secretes a special enzyme - bile, which disarms toxins and removes them from the body, including the poisons of alcohol, drugs and drugs.
The role of skin in excretion processes
All excretory organs are indispensable. After all, if their functioning is disturbed, toxic substances - toxins - will accumulate in the body. Of particular importance in the implementation of this process is the largest human organ - the skin. One of its most important functions is the implementation of thermoregulation. During intensive work, the body generates a lot of heat. It can build up and cause overheating.
Leather regulates the intensity of heat transfer, keeping only its required amount. Together with sweat, in addition to water, mineral s alts, urea and ammonia are removed from the body.
How does heat transfer work?
Man is a warm-blooded creature. This means that the temperature of his body does not depend on climatic conditions.conditions in which he lives or is temporarily located. Organic substances that come with food: proteins, fats, carbohydrates - are broken down in the digestive tract to their constituents. They are called monomers. During this process, a large amount of thermal energy is released. Since the ambient temperature is most often below body temperature (36.6 degrees), according to the laws of physics, the body gives off excess heat to the environment, i.e. in the direction where it is smaller. This maintains temperature equilibrium. The process of giving off and generating heat by the body is called thermoregulation.
When does a person sweat the most? When it's hot outside. And in the cold season, sweat is practically not released. This is because it is not profitable for the body to lose heat when there is not much of it anyway.
The nervous system also affects the process of thermoregulation. For example, when your palms sweat during an exam, it means that in a state of excitement, the vessels dilate and heat transfer increases.
The structure of the urinary system
The urinary system plays an important role in the processes of excretion of metabolic products. It consists of paired kidneys, ureters, bladder, which opens outward through the urethra. The figure below ("Organs of Excretion") illustrates the location of these organs.
Kidneys are the main excretory organ
The human excretory organs begin with the kidneys. These are paired bean-shaped organs. They are located inabdominal cavity on both sides of the spine, to which the concave side is turned.
Outside, each of them is covered with a shell. Through a special recess called the renal gate, blood vessels, nerve fibers and ureters enter the organ.
The inner layer is formed by two types of substances: cortical (dark) and brain (light). Urine is formed in the kidney, which is collected in a special container - the pelvis, coming from it into the ureter.
Nefron is the elementary unit of the kidney
The excretory organs, in particular the kidney, consist of elementary structural units. It is in them that metabolic processes occur at the cellular level. Each kidney consists of a million nephrons - structural and functional units.
Each of them is formed by a renal corpuscle, which, in turn, is surrounded by a goblet capsule with a tangle of blood vessels. Urine is initially collected here. Convoluted tubules of the first and second tubules depart from each capsule, opening with collecting ducts.
Mechanism of urine production
Urine is formed from blood by two processes: filtration and reabsorption. The first of these processes occurs in the nephron bodies. As a result of filtration, all components are released from the blood plasma, except for proteins. Thus, in the urine of a he althy person should not be this substance. And its presence indicates a violation of metabolic processes. As a result of filtration, a liquid is formed, whichcalled primary urine. Its quantity is 150 liters per day.
After comes the next stage - reabsorption. Its essence lies in the fact that all substances useful for the body are absorbed from the primary urine into the blood: mineral s alts, amino acids, glucose, a large amount of water. As a result, secondary urine is formed - 1.5 liters per day. In this substance, a he althy person should not have the monosaccharide glucose.
Recycled urine is 96% water. It also contains sodium, potassium and chloride ions, urea and uric acid.
Reflex nature of urination
From each nephron, secondary urine enters the renal pelvis, from which it flows down the ureter into the bladder. It is a muscular unpaired organ. The volume of the bladder increases with age and in an adult reaches 0.75 liters. Outwardly, the bladder opens with the urethra. At the exit, it is limited by two sphincters - circular muscles.
In order for the urge to urinate to occur, about 0.3 liters of fluid must accumulate in the bladder. When this happens, the wall receptors are irritated. Muscles contract and sphincters relax. Urination occurs voluntarily, i.e. an adult is able to control this process. Urination is regulated by the nervous system, its center is located in the sacral spinal cord.
Functions of excretory organs
The kidneys play an important role in the process of removing the end products of metabolism from the body,regulate water-s alt metabolism and maintain the constancy of the osmotic pressure of the liquid medium of the body.
The excretory organs cleanse the body of toxins, maintaining a stable level of substances necessary for the normal full functioning of the human body.
