Excretory organ system
Excretory organs include:
- kidneys;
- leather;
- lungs;
- salivary and gastric glands.
The kidneys rid a person of excess water, accumulated salts, toxins formed due to the consumption of too fatty foods, toxins and alcohol. They play a significant role in the removal of breakdown products of drugs. Thanks to the work of the kidneys, a person does not suffer from an excess of various minerals and nitrogenous substances.
The lungs maintain oxygen balance and act as both internal and external filters. They promote the effective removal of carbon dioxide and harmful volatile substances formed inside the body, and help get rid of liquid vapors.
Gastric and salivary glands - help remove excess bile acids, calcium, sodium, bilirubin, cholesterol, as well as undigested food debris and metabolic products. The gastrointestinal tract rids the body of heavy metal salts, drug impurities, and toxic substances. If the kidneys cannot cope with their task, the load on this organ increases significantly, which can affect the efficiency of its work and lead to failures.
The skin carries out its metabolic function through the sebaceous and sweat glands. The process of sweating removes excess water, salts, urea and uric acid, as well as about two percent of carbon dioxide. The sebaceous glands play a significant role in performing the protective functions of the body, secreting sebum, consisting of water and a number of unsaponifiable compounds. It prevents harmful compounds from penetrating through the pores. The skin effectively regulates heat transfer, protecting a person from overheating.
I. The concept of the excretion system. The kidneys are the main excretory organ.
The process of excretion ensures that the body is freed from metabolic end products, foreign and toxic substances, as well as excess water, salts and organic compounds. The following organs are involved in the process of excretion in humans.
Lungs - remove CO2, water, some volatile substances from the body, for example, ether and chloroform vapors during anesthesia, alcohol vapors during intoxication.
Skin glands - with sweat they remove water and salts, some organic substances (in particular urea), and during intense muscular work - lactic acid.
The salivary, gastric, intestinal glands and pancreas secrete heavy metals, a number of drugs and foreign organic compounds.
Liver – removes a number of nitrogen metabolic products from the blood.
The kidneys are the main excretory organs, their functions:
1) excretory function - release from the body of the final products of nitrogen metabolism and foreign substances, excess organic substances (glucose, amino acids, etc.);
2) volume regulation – participation in the regulation of blood volume and extracellular fluid;
3) osmoregulation – regulation of the concentration of osmotically active substances in the blood and other body fluids;
4) ionic regulation – regulation of the ionic composition of blood serum and the ionic balance of the body;
5) participation in the regulation of acid-base status (stabilization of blood pH);
6) endocrine function - participation in the regulation of the blood system, modulation of the action of hormones due to the release of biologically active substances into the blood;
7) metabolic function - participation in the metabolism of proteins, lipids and carbohydrates.
Each human kidney contains about 1 million functional units - nephrons, in which urine is formed. Each nephron begins with a renal, or Malpighian, corpuscle - a double-walled glomerular capsule (Bowman's capsule), inside which there is a glomerulus of capillaries (Fig. 1). The internal cavity between the visceral and parietal layers of the capsule passes into the lumen of the proximal convoluted tubule. The next section of the nephron is the thin descending part of the loop of nephron (loop of Henle). The descending part of the loop may descend deep into the medulla, where the tubule bends 180°, and turns towards the renal cortex, forming the ascending part of the nephron loop. It may include a thin and always has a thick ascending part, which rises to the level of the glomerulus of its own nephron, where the distal convoluted tubule begins. This section of the tubule necessarily touches the glomerulus between the afferent and efferent arterioles. The terminal section of the nephron is a short connecting tubule that flows into the collecting duct. Beginning in the renal cortex, the collecting ducts pass through the medulla and open into the cavity of the renal pelvis. The diameter of the glomerular capsule is about 0.2 mm, the length of the tubules of one nephron reaches 50 mm.
Rice. 1. The structure of the nephron. A – juxtamedullary nephron; B – intracortical iefron; 1 – renal corpuscle, including the glomerular capsule and the glomerulus of capillaries; 2 – proximal convoluted tubule; 3 – proximal straight tubule; 4 – descending thin limb of the nephron loop; 5 – ascending thin limb of the nephron loop; 6 – distal straight tubule (thick ascending limb of the nephroic loop); 7 – dense spot of the distal tubule; 8 – distal convoluted tubule; 9 – connecting tubule; 10 – collecting duct of the renal cortex; 11 – collecting duct of the outer medulla; 12 – collecting duct of the internal medulla. A broken line with a sharp bend in the cortex marks the area of the medulla.
There are usually two types of nephrons in the kidney: intracortical and juxta-medullary (“peri-brain”). Juxtamedullary ones are larger than superficial ones, their glomeruli lie deeper - at the border of the cortex and medulla, they have longer nephron loops descending into the inner medulla of the kidney.
The renal cortex contains the renal glomeruli, proximal and distal tubules, and connecting sections. In the outer strip of the outer medulla there are descending and thick ascending sections of the nephron loops, collecting ducts; The inner medulla contains thin sections of nephron loops and collecting ducts. The location of each part of the nephron in the kidney is extremely important and determines the form of participation of certain nephrons in the activity of the kidney, in particular in the osmotic concentration of urine.
Blood supply to the kidney. About 1/5 of the blood coming from the heart to the aorta passes through the kidneys. Blood flow through the renal cortex is the highest level of organ blood flow. The peculiarity of renal blood flow is that under conditions of changes in blood pressure within a wide range (from 90 to 190 mm Hg), it remains constant. This is due to a special system of self-regulation of blood circulation in the kidney.
Short renal arteries arise from the abdominal aorta, branch in the kidney into smaller and smaller vessels, and one afferent arteriole enters the glomerulus. Here it breaks up into capillary loops, which, merging, form the efferent arteriole, through which blood flows from the glomerulus. The diameter of the efferent arteriole is narrower than the afferent one. Soon after leaving the glomerulus, the efferent arteriole again breaks up into capillaries, forming a dense network around the proximal and distal convoluted tubules. Thus, most of the blood in the kidney passes through the capillaries twice - first in the glomerulus, then at the tubules. The difference in the blood supply to the juxtamedullary nephron is that the efferent arteriole does not break up into a peritubular capillary network, but forms straight vessels descending into the renal medulla. These vessels provide blood supply to the renal medulla; blood from the peritubular capillaries and vasa recta flows into the venous system and enters the inferior vena cava through the renal vein.
An important role is played by the juxtaglomerular apparatus - something like a triangle, the two sides of which are represented by the afferent and efferent arterioles approaching the glomerulus, and the base by so-called cells. dense spot of the distal tubule. This apparatus is involved in the secretion of renin and other biologically active substances.
Methods for studying kidney function. When studying kidney function, the “purification” (clearance) method is used: comparing the concentrations of certain substances in the blood and urine makes it possible to calculate the values of the main processes underlying urine formation. In addition, methods of micropuncture, microperfusion, microelectrode technology and ultramicroanalysis of liquid extracted with a micropipette are used, which makes it possible to study the mechanism of transport of substances through the membranes of tubular cells.
II. Glomerular filtration. Formation of primary urine
The formation of urine is the result of three sequential processes.
1. Glomerular filtration of fluid from blood plasma into the capsule of the renal glomerulus, resulting in the formation of primary urine.
2. Tubular reabsorption is the process of reabsorption of filtered substances and water.
3. Secretion. The cells of some sections of the tubule transfer a number of substances from the extracellular fluid into the lumen of the tubule or secrete substances synthesized in the cell of the tubule.
Glomerular filtration. Ultrafiltration of water and low molecular weight components from blood plasma occurs through the glomerular filter. This filter is almost impenetrable to high molecular weight substances. The ultrafiltration process is determined by the difference between the hydrostatic pressure of the blood, the hydrostatic pressure in the glomerular capsule and the oncotic pressure of blood plasma proteins. The total surface of the glomerular capillaries is larger than the total surface of the human body. The filtering membrane consists of three layers: endothelial cells of the capillaries, basement membrane and epithelial cells of the visceral (inner) layer of the capsule - podocytes.
Podocyte membranes are the most important. They limit the filtration of substances whose molecular diameter is greater than 6 nm. Therefore, inulin (a fructose polymer) freely penetrates into the nephron lumen, but only 3% of hemoglobin and less than 1% of serum albumin. The ultrafiltrate (primary urine) is similar to plasma in terms of the total concentration of osmotically active substances, glucose, urea, etc. It contains only traces of protein.
I use inulin to measure filtration rate. Normally, in men it is about 125 ml/min in both kidneys, in women it is approximately 110 ml/min. The filtration value measured using inulin, also called the inulin clearance coefficient (or inulin clearance), shows how much of the blood plasma is cleared of inulin during this time. To measure the clearance of inulin, it is necessary to continuously infuse its solution into a vein. Obviously, this is very difficult and not always feasible in the clinic, so creatinine, a natural component of plasma, is more often used, although with its help the glomerular filtration rate is measured less accurately.
In a healthy person, water enters the lumen of the nephron as a result of filtration in the glomeruli, is reabsorbed in the tubules, and as a result, the concentration of inulin increases. The inulin concentration index (inulin concentration in urine/inulin concentration in plasma) indicates how many times the volume of the filtrate decreases as it passes through the tubules. Based on it, it can be determined whether substance X is reabsorbed or secreted by tubular cells. If the concentration indicator of a given substance X is less than that for inulin, then this indicates the reabsorption of substance X in the tubules; if it is greater, then this indicates its secretion.
urinary system
The main role among the human excretory organs is occupied by the kidneys and the urinary system, which include:
- bladder;
- ureter;
- urethra.
The kidneys are a paired legume-shaped organ, about 10-12 cm long. An important excretory organ is located in the lumbar region of a person, protected by a dense layer of fat and somewhat mobile. That is why, it is little susceptible to injury, but is sensitive to internal changes within the body, human nutrition and negative factors.
Each kidney in an adult weighs about 0.2 kg and consists of a pelvis and the main neurovascular bundle that connects the organ with the human excretory system. The pelvis serves to communicate with the ureter, and that with the bladder. This structure of the urine excretory organs allows you to completely close the circulatory cycle and effectively perform all assigned functions.
The structure of both kidneys consists of two interconnected layers:
- cortical - consists of nephron glomeruli, serves as the basis for kidney function;
- cerebral - contains a plexus of blood vessels, supplies the organ with necessary substances.
The kidneys transport all human blood through themselves in 3 minutes, and therefore are the main filter. If the filter is damaged, an inflammatory process or kidney failure occurs, metabolic products do not pass through the ureter into the urethra, but continue to move throughout the body. Toxins are partially eliminated through sweat, metabolic products through the intestines, and also through the lungs. However, they cannot completely leave the body, and therefore acute intoxication develops, which poses a threat to human life.
Urethra
In women and men, the urethra differs in its structure. This is due to the difference in genital organs.
Structure
The canal itself consists of 3 membranes, like the ureter. Because women have a urethra
In short, than in men, women are more often exposed to various diseases and inflammations of the urogenital tract.
Functions
- In men, the canal performs several functions: excretion of urine and sperm. The fact is that the vas deferens ends in the canal tube, through which sperm flows through the canal into the head of the penis.
- In women, the urethra is a tube 4 cm long and performs only the function of excreting urine.
Functions of the urinary system
The main functions of the excretory organs are to remove toxins and excess mineral salts from the body. Since the main role of the human excretory system is performed by the kidneys, it is important to understand how exactly they purify the blood and what can interfere with their normal functioning.
When blood enters the kidneys, it enters their cortex, where rough filtration occurs due to the nephron glomeruli. Large protein fractions and compounds return to the human bloodstream, supplying him with all the necessary substances. Small debris is sent to the ureter to leave the body along with urine.
Here tubular reabsorption manifests itself, during which the reabsorption of useful substances from primary urine into the human blood occurs. Some substances undergo reabsorption with a number of features. If there is an excess of glucose in the blood, which often occurs with the development of diabetes, the kidneys cannot cope with the entire volume. A certain amount of glucose released may appear in the urine, which signals the development of a serious disease.
When processing amino acids, it happens that several subspecies can be present in the blood at the same time, carried by the same carriers. In this case, reabsorption may be inhibited and put strain on the organ. Protein normally should not appear in urine, but under certain physiological conditions (high temperature, heavy physical work) it can be detected in small quantities. This condition requires observation and control.
Thus, the kidneys completely filter the blood in several stages, leaving no harmful substances behind. However, due to an excess of toxins in the body, the functioning of one of the processes in the urinary system may be disrupted. This is not a pathology, but requires consultation with a specialist, since with constant overload the organ quickly fails, causing serious damage to human health.
In addition to filtration, the urinary system:
- regulates fluid balance in the human body;
- maintains acid-base balance;
- takes part in all metabolic processes;
- regulates blood pressure;
- produces necessary enzymes;
- ensures normal hormonal levels;
- helps improve the absorption of vitamins and minerals into the body.
If the kidneys stop working, harmful fractions continue to wander through the vascular bed, increasing concentration and leading to slow poisoning of a person with metabolic products. Therefore, it is so important to maintain their normal operation.
Selection and its meaning
As a result of the excretion process, those metabolic products that cannot be used are removed from the body. The breakdown products of various substances, formed in the cells of the body in the process of various metabolic reactions, first enter the internal environment and then are excreted from the body. The significance of excretion is to maintain the constancy of the internal environment of the body.
The main organs of excretion are the kidneys, through which nitrogen-containing protein breakdown products, excess water, some salts and other substances are removed. Thus, the kidneys maintain a constant ratio of water and salts in the body.
The release of metabolic products is also carried out in other ways. Through the lungs, carbon dioxide, a small amount of water vapor, and some volatile substances are removed from the human body. Sweat glands secrete water, urea, ammonia, and salts through the outer integument of the body. Salts of toxic heavy metals are removed from the body through the intestines with feces.
Preventive measures
In order for the entire excretory system to work smoothly, it is necessary to carefully monitor the work of each of the organs related to it, and if there is the slightest malfunction, contact a specialist. For proper functioning of the kidneys, hygiene of the excretory organs of the urinary system is necessary. The best prevention in this case is the minimum amount of harmful substances consumed by the body. It is necessary to carefully monitor your diet: do not drink alcohol in large quantities, reduce the content of salted, smoked, fried foods in your diet, as well as foods oversaturated with preservatives.
Other human excretory organs also need hygiene. If we talk about the lungs, then it is necessary to limit exposure to dusty rooms, places where toxic chemicals accumulate, and confined spaces with a high content of allergens in the air. You should also prevent lung diseases, conduct a fluorographic examination once a year, and eliminate foci of inflammation in a timely manner.
It is equally important to maintain normal functioning of the gastrointestinal tract. Due to insufficient bile production or the presence of inflammatory processes in the intestines or stomach, fermentation processes may occur with the release of rotting products. Once in the blood, they cause manifestations of intoxication and can lead to irreversible consequences.
As for the skin, everything is simple. They should be regularly cleaned of various contaminants and bacteria. However, you can't overdo it. Excessive use of soap and other detergents can disrupt the functioning of the sebaceous glands and lead to a decrease in the natural protective function of the epidermis.
The excretory organs accurately recognize which cells of substances are necessary to maintain all life systems, and which can cause harm. They cut off all excess and remove it with sweat, exhaled air, urine and feces. If the system stops working, the person dies. Therefore, it is important to monitor the functioning of each organ and if your health worsens, immediately contact a specialist for examination.
