The main excretory organ of the human body, which removes a significant part of the end products of metabolism, are the kidneys. Most people usually have at least the slightest understanding of their importance. The first serious acquaintance with the meaning and peculiarity of the kidneys is given within the framework of the 8th grade school program - "The structure and functions of the human kidneys." Being a powerful filter, they daily pump all the blood of the body through themselves and cleanse it of toxins, toxins and decay products. It is from them that the normal operation of all other systems will depend. These are the very organs to which special attention should be paid and whose importance will never be overestimated. This article will focus on the functions and structure of the kidneys.
Location of the kidneys in the body
The human kidney is a paired excretory (excretory) organ that enters the urinary system. It is located on the back wall of the abdominal cavity, on the sides of the spinal column at the level of the lower back. The size of a he althy kidney is 10-12 cm. Being at the height of the twelfth thoracic and second lumbar vertebrae, the kidneys lie opposite each other, while the position of the left is slightly higher than the right, witha small difference of 1.5-2.0 cm. Fixation of the kidneys in their bed is facilitated by the peritoneum and intra-abdominal pressure. A decrease in intra-abdominal pressure caused by severe weight loss in a short period or stretching of the abdominal press affects the descent of the kidneys.
The position of the kidneys will also depend on the age of the person, his fatness and physique. Interestingly, in the female and male body, the kidneys are located differently: in men, they are half a vertebra higher. Their weight, depending on the individuality of the body, ranges from 120 to 200 grams, and the right kidney will be slightly heavier than the left.
Structure of the kidney
Anatomically, the appearance of the kidneys resembles beans with slightly rounded poles, upper and lower. Outside, they are covered with a dense fibrous shell-capsule of connective adipose tissue. On the concave side of the kidneys, which faces the spine, are the renal gates. They lead to the renal sinus, the place where the beginning of the ureter is located, blood vessels, lymphatic vessels and nerves enter and exit.
The kidney is divided into two layers: lying closer to the surface (darker) - cortical (thickness 4 mm) and inner (slightly lighter) - cerebral. The cortical substance, climbing into the medulla, breaks it into renal pyramids. They are clearly visible in the photo of the structure of the human kidney (dark segments). The medulla is based on parenchymal tissue and stroma, where nerve fibers and renal tubules are located. In the cortical layer are nephrons, which are the main structural andfunctional unit of the kidney.
Nefron is a morpho-functional unit
The microscopic structure of the kidneys, an organ that performs a number of important functions for the body, is very complex. These are tubular glands that have their own constituent elements - nephrons. In one kidney, there are about one million of them. The size of one nephron in length can vary from 2 to 5 cm, and their joint length (in both kidneys) will be about 120 km. The structure of the nephron gives an understanding of the basic function of the kidneys.
The nephron is a vascular tangle covered by the Shumlyansky-Bowman capsule, which looks like a cup under a microscope. The capsule consists of the thinnest partition - the renal membrane. Through this septum, the incoming blood is purified and urine is filtered. In each capsule, with a glomerulus of arterial capillaries inside, self-organized combinations are formed - Malpighian bodies. They can be seen on the kidney without a microscope, they look like red dots. The result of a rather complex mechanism of purification and absorption is the formation of the final urine.
Kidney process
On an average day, he althy human kidneys produce and excrete approximately 1.5-2.0 liters of secondary urine. They carry quite a lot of weight. The countercurrent-multiplier system of tubules is responsible for all the work of the kidneys and the excretion of urine.
Malpighian body of the nephron due to increased capillary pressurethe glomerulus cleans the blood plasma and thereby gives rise to the formation of a fluid containing substances used by the body. The result of such work will be 150-180 liters of primary urine per day. At the next stage of the process, the complex of tubules, through the secretion of various substances and reabsorption (or reabsorption of water from the primary urine), forms the secondary. The fluid passes through the collecting duct into the papillary duct and through the holes goes into the small renal calyces, and from there it enters the large ones. At the exit, it ends up in the renal pelvis and enters the ureter.
The peculiar structure and work of the kidneys contributes to the rapid removal of harmful substances and decay products from the human body. The whole process is regulated by the nervous and humoral systems.
Regulation of the kidneys
Regulation of kidney function is carried out by humoral and nervous factors. At the same time, nervous regulation is less pronounced, it affects the filtration process more, while humoral regulation affects the reabsorption process. Regulation occurs by increasing and decreasing blood flow through the kidneys. Like all capillaries, the vessels of the glomerulus narrow and expand, which leads to a decrease or increase in the lumen in them. This, in turn, will affect blood filtration.
The human urinary reflex center is located in the spinal cord. Its activity is controlled by the higher part of the central nervous system - the cerebral cortex. As a result, a person can meaningfully restrain and release the process of urination.
Kidney circulation
Understanding the functions and structure of the kidneys will be incomplete without knowing their blood supply. In just one day, 1500–1700 liters of blood passes through this organ. With such large volumes of blood flow, the blood supply to the kidneys is different from other organs in the human body.
The kidneys are fed through arteries originating from the abdominal aorta. It is very peculiar and shows the original system of blood vessels. The artery entering the renal gate diverges into segmental arteries, which, in turn, sequentially diverge into small vessels. Many interlobular arteries branch off into the cortical layer, from which the arteries bearing arterioles branch off. The latter, entering the nephron capsule, crumble into the primary capillary network.
At the next stage, the primary capillary network passes into the efferent arterioles, which break up into capillaries supplying the tubules - the secondary capillary network. The sequence of this blood flow is as follows: the blood is collected in the venules, then in the interlobular veins, then flows into the arcuate and interlobar veins, which, when meeting, together form the renal vein.
Excessive blood flow and the peculiar design of the capillary network of the kidney make it possible to quickly rid the body of decay products.
Kidney Functions
Careful study of the biology of the structure of the kidneys has helped to better understand the functions they perform. In addition to the main excretory function, the kidneys have other equally significant responsibilities.
- Endocrine function. Kidney cells have the ability to synthesize and produce the necessary hormones and active substances (renin, erythropoietin, prostaglandins) that affect the entire body.
- Ion-regulating function (regulation of acid-base balance). The kidneys provide a balanced ratio of acidic and alkaline components of blood plasma.
- Metabolic function. The kidneys maintain a constant level of proteins, carbohydrates and lipids in body fluids.
- Osmoregulatory function. The kidneys provide the necessary concentration of osmotically active blood substances in the internal environment of the body.
- Hematopoietic function. The kidneys take part in hematopoiesis through the produced hormone erythropoietin, which is responsible for the formation of red blood cells.
Causes of kidney disease
Most often, kidney disease begins imperceptibly. And it should be noted that they all differ from each other, for example, nephritis and pyelonephritis. The difference in their appearance and course is determined by the structure of the kidneys.
A number of the main causes that provoke diseases of this organ are as follows: inflammatory processes in the body, hypothermia, antibiotic abuse, a sedentary lifestyle, sudden weight loss, the use of carbonated drinks, malnutrition (smoked meats, s alty foods), physical overload (lifting weights), passion for alcoholic beverages.
Interesting about the kidneys
- The kidneys of a pregnant woman endure the load ten times more thanan ordinary person.
- Kidney disease worsens most often in winter.
- Sunbathing men have a lower risk of kidney cancer.
- Kidney stones were removed by people as early as the 6th-5th centuries. BC e.
- Sleep disturbance and nightmares can be directly linked to kidney disease.
- Over 70 years of human life, the kidneys filter an average of 40 million liters of blood.
- The very first description of the structure of the kidney was given by the Italian researcher M. Malpighi (1628–1694).
- The kidneys are the most frequently transplanted organ in medicine: out of 100,000 transplanted organs, 70,000 occur in the kidneys.
- 80% of people have kidney failure.
- The volume of human urine produced in one day is comparable in volume to Niagara Falls functioning for 20 minutes.
Chinese doctors call the kidneys "the first mother of man", the center of his life force.
