The body is an amazing collection of organs and tissues that work together to maintain human life. And the main process that supports life is metabolism. As a result of the breakdown of substances, the energy necessary for the flow of basic biological processes is synthesized. However, along with energy, potentially harmful metabolic products are also formed. They must be removed from the cell, interstitial fluid and blood by the kidneys. In the kidneys, filtration occurs in the glomerular apparatus, a special structure of the active nephron, into which the afferent arteriole flows.
Feature of the structure of the nephron
Nefron - a collection of cells that form a capsule and a glomerulus with channels extending from it, intended forblood plasma filtration and urine diversion. This is the elementary functional unit of the kidney responsible for urination. The nephron consists of a glomerulus that has its own capsule. The afferent arteriole, a blood vessel, flows into it, through which blood enters the glomerulus. Many small arterioles depart from the afferent arteriole, which form a glomerulus and gather into a larger one - the efferent one.
The latter is much smaller in diameter than the bringing one, which is necessary to maintain high pressure (about 120 mm Hg) at the inlet. Due to this, the hydrostatic pressure in the glomerulus increases, and therefore almost all the liquid is filtered, and not carried out into the efferent arteriole. Only thanks to the hydrostatic pressure, approximately equal to 120 mm of mercury, there is such a process as renal filtration. At the same time, in the kidneys, blood filtration occurs in the glomerulus of the nephron, and its speed is almost 120 ml per minute.
Renal filtration characteristic
Globular filtration rate is one of the indicators by which the functional state of the kidneys is determined. The second indicator is reabsorption, which is normally almost 99%. This means that almost all of the primary urine that has passed from the nephron glomerulus to the convoluted tubule after passing through the descending tubule, the loop of Henle and the ascending tubule is absorbed back into the blood along with nutrients.
The blood flow to the kidneys is carried out through the arteries, which are normalconsume a quarter of the total minute volume of blood circulation, and the filtered one is discharged through the veins. This means that if the systolic output of the left ventricle of the heart is 80 ml, then 20 ml of blood will be captured by the kidneys, and another 20 ml by the brain. The remaining 50% of the total systolic volume provides for the needs of the rest of the organs and tissues of the body.
The kidneys are organs that take a huge part of the blood circulation, but they need blood not so much for metabolism as for filtering. This is a very fast and active process, the speed of which is quite easy to track using the example of intravenous dyes and radiopaque agents. After their intravenous administration in the kidneys, blood filtration occurs in the glomerular apparatus of the cortical substance. And already 5-7 minutes after being hit, it can be seen in the renal pelvis.
Filtration in the kidneys
In fact, the contrast travels from the venous bed to the lung, then to the heart and then to the renal artery in 20-30 seconds. In another minute, it enters the renal glomerulus, and after a minute, through the collecting ducts located in the pyramids of the kidneys, it collects in the renal calyces and is released into the pelvis. All this takes about 2.5 minutes, but only at 5-7 minutes the contrast concentration in the pelvis rises to values that allow the excretion to be seen on x-rays.
That is, the filtration of drugs, poisons or metabolic products actively takes place after 2.5 minutes in the blood. It's very fasta process that is possible due to the special structure of the nephron. In the kidneys, blood filtration occurs in these structures, the glomeruli of which are located in the cortical substance. In the medulla of the kidneys, only the tubules of the nephron are located. Therefore, it is correct to say that filtration occurs in the cortical layer of organs.
Many are mistaken when they say that in the kidneys, blood filtration occurs in the pyramids. This is a mistake, since they mainly contain only the collecting ducts of the nephron, convoluted, descending and ascending tubules, as well as the loop of Henle. This means that in the pyramids, the main process is the reabsorption and concentration of urine, after which it is collected and excreted into the renal pelvis. The filtration itself takes place in the cortical layer of the kidney, which is richly supplied with blood.
Special functions of the renal tubules
In the kidneys, blood filtration occurs in the capsules of the nephrons, more precisely, in the glomerular apparatus. Primary urine is formed here, which is a blood plasma without the main high-molecular proteins. The epithelium that lines the inside of the renal tubules has special functions. First, it is able to absorb water and electrolytes, returning it to the vascular bed.
Secondly, epithelial cells can absorb low molecular weight proteins, which will also be transferred to the blood without destroying their structure. Thirdly, the epithelium of the nephron tubules is capable of independently synthesizing amino acids by transamination and glucose by gluconeogenesis from amino acid residues. But this process is not chaotic, but regulatedbody.
This means that epithelial cells have a number of receptors that receive a signal from mediator molecules, activating either the synthesis of amino acids or glucose. The fourth feature of the epithelial lining of the renal glomeruli is the ability to absorb monosaccharides in the form of glucose-6-phosphate.
CV
Kidneys are organs of the urinary system in which filtration takes place. Thanks to it, nephrons remove water-soluble compounds from the blood, maintaining the acid-base balance of the body. A common misconception is that in the kidneys, blood filtration occurs in the convoluted tubules. In fact, already filtered liquid - primary urine - enters the convoluted tubule from the glomerular capsule. In the convoluted glomerulus, the main task of the epithelium is the absorption of water and the implementation of the concentration function.
