The main organ of excretion of the human body, which removes a significant part of the final metabolic products, 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 as part of the 8th grade school curriculum - “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 bodies that should be given special attention and whose importance will never be overestimated. This article will focus on the functions and structure of the kidneys.
The location of the kidneys in the body
Human kidneys are 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 healthy kidney is 10-12 cm. Located 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, with a slight difference of 1.5-2.0 cm. Fixation of the kidneys in them the bed contributes to the peritoneum and intra-abdominal pressure. A decrease in intra-abdominal pressure caused by severe weight loss for a short period or by stretching the abdominal press affects the lowering of the kidneys.
The position of the kidneys will also depend on the person’s age, fatness and physique. It is interesting that in the female and male body the kidneys are not located the same way: in men they are higher by half the vertebra. Their weight, depending on the personality of the body, is from 120 to 200 grams, and the right kidney will be slightly heavier than the left.
Kidney structure
Anatomically, the appearance of the kidneys resembles beans with slightly rounded poles, upper and lower. Outside, they are covered with a dense fibrous membrane-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, the blood vessels, lymph vessels and nerves enter and exit.
The kidney is divided into two layers: lying closer to the surface (darker) - cortical (4 mm thick) and internal (slightly lighter) - cerebral. The cortical substance, climbing into the cerebral, breaks it down into the renal pyramids. They are clearly visible in the photo of the structure of the human kidney (dark segments). The brain substance is based on parenchymal tissue and stroma, where nerve fibers and renal tubules are located. Nephrons are located in the cortical layer, which are the main structural and functional unit of the kidney.
Nephron - a morpho-functional unit
The microscopic structure of the kidneys, an organ that performs a number of essential functions for the body, is very difficult. These are tubular glands, which have their 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 combined length (in both kidneys) will be about 120 km. The structure of the nephron provides an understanding of the basic function of the kidneys.
The nephron is a vascular bundle covered by a Shumlyansky-Bowman capsule, which looks like a cup under a microscope. The capsule consists of the thinnest septum - 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, independently 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 cleansing and absorption is the formation of final urine.
Kidney process
On average, healthy human kidneys produce and excrete approximately 1.5–2.0 liters of secondary urine per day. They carry a fairly large load. For all the work of the kidneys and the excretion of urine, the countercurrent multiplication system of the tubules is responsible.
Due to the increased capillary pressure of the glomerulus, the malpigian body of the nephron cleanses the blood plasma and thereby gives rise to the formation of a fluid containing the substances spent by the body. The result of this 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 reverse absorption (or reabsorption of water from primary urine) forms a secondary one. The fluid through the collecting duct passes into the papillary and through the holes goes into the small renal calyces, and from there it enters the large ones. At the exit, it appears in the renal pelvis and enters the ureter.
The peculiar structure and work of the kidneys contributes to the rapid elimination of harmful substances and decay products from the human body. The whole process is regulated by the nervous and humoral systems.
Kidney regulation
The regulation of kidney function is carried out by humoral and nerve factors. At the same time, nervous regulation is less pronounced, it affects the filtering process more, while humoral regulation - on the reabsorption process. Regulation occurs by increasing and decreasing blood flow through the kidneys. Like all capillaries, the glomerular vessels narrow and expand, which leads to a decrease or increase in the clearance in them. This, in turn, will affect blood filtration.
The center of the urinary reflex in humans is located in the spinal cord. Its activity is controlled by the higher part of the central nervous system - the cortex of the cerebral hemispheres. As a result, a person can consciously restrain and release the process of urination.
Kidney circulation
Understanding the functions and structure of the kidneys will be incomplete without knowledge of their blood supply. In one day only 1,500-1,700 liters of blood pass through this organ. With such large volumes of blood flow, the blood supply to the kidneys is different from other organs of the human body.
Kidney nutrition is via arteries originating from the abdominal aorta. It is very peculiar and is an 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 depart into the cortical layer, from which arteries bearing arterioles branch. The latter, entering the nephron capsule, are scattered on the primary capillary network.
At the next stage, the primary capillary network passes into the efferent arterioles, which decompose into capillaries supplying the tubules - the secondary capillary network. The sequence of this blood flow is as follows: blood collects into venules, then into interlobular veins, then flows into the arc and interlobular veins, which, when met, form the renal vein together.
Abundant blood flow and a peculiar design of the capillary network of the kidney make it possible to quickly rid the body of decay products.
Kidney function
A thorough study in the biology of the structure of the kidneys helped to better understand their functions. In addition to the main excretory, 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 acid 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 participate in hematopoiesis through the produced hormone erythropoietin, which is responsible for the formation of red blood cells.
Causes of Renal Disease
Most often, kidney diseases begin unnoticed. And it should be noted that they all differ among themselves, for example, jade and pyelonephritis. The difference in their appearance and course is determined by the structure of the kidneys.
A number of main reasons that provoke diseases of this organ are as follows: inflammatory processes in the body, hypothermia, abuse of antibiotics, a sedentary lifestyle, sudden weight loss, the use of carbonated drinks, improper nutrition (smoked foods, salty foods), physical overload (weight lifting), and alcohol addiction drinks.
Interesting about the kidneys
- The kidneys of a pregnant woman carry a load of tens of times more than that of an ordinary person.
- Kidney disease worsens most often in winter.
- Sunbathing men have a lower risk of kidney cancer.
- People learned to remove kidney stones in the VI-V century. BC e.
- Sleep disturbance and nightmares can be directly related 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. Malpigi (1628–1694).
- The kidneys are the most frequent transplanted organ in medicine: out of 100 thousand transplanted organs, 70 thousand are accounted for by the kidneys.
- 80% of people have kidney failure.
- The volume of human urine produced in one day is comparable in volume to Niagara Falls, which has been functioning for 20 minutes.
Chinese doctors call the kidneys "the first mother of a person", the center of his vitality.