Function of the kidney


The paired kidneys are part of the urine-producing system and are located at the level of the 11th and 12th ribs below the diaphragm. A fat capsule envelops both kidneys and adrenal glands. Pain from kidney disease mostly projects onto the lumbar region of the middle back.

The function of the kidneys is based on a complex filter system that forms urine from the blood and its components. The most important tasks include the regulation of the water balance and the electrolyte and acid-base balance, the excretion of so-called urinary substances and the control of blood pressure. In addition, the kidneys produce important hormones such as renin and erythropoietin and are involved in the metabolism of sugar.

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Function of the renal medulla

The kidney parenchyma describes the kidney tissue in its entirety. It is made up of the outer renal cortex and the inwardly adjacent cortex Renal medulla together. The kidney medulla, too Medulla renalis called, consists of around 15 to 20 individual pyramid-shaped, ray-like units. The basis of the Marrow pyramids adjoins the renal cortex. The pyramids merge and form about eight pyramid points with the finest pores. The pointed end of the medullary pyramids points into the interior of the kidney and protrudes into the calyxes (Calix renalis) into it. The resulting urine flows from the marrow into the calyxes, which together contain the Renal pelvis (Pelvis renalis) form.

The Function of the renal medulla is based on the formation of the secondary urine. The primary urine coming from the renal cortex flows through the tubular system, the renal tubules. A large part of the fluid and the substances it contains are now absorbed and returned to the bloodstream. A smaller part is excreted in concentrated form as urine.

Function of the renal cortex

The renal cortex (Renal cortex) is, like the kidney medulla, part of the kidney tissue. you bordered on the outside by the renal capsule and on the inside by the renal medulla. As Columnae renalis, Kidney columns, pulls the bark between the medullary pyramids to the Renal sinus, the kidney bay. The part of the bark directly below the capsule is covered with delicate medullary rays (Radii medullares), which are functionally assigned to the renal medulla.

The kidney cortex consists of around one million Nephronsrepresenting the functional units of the bark. They play an important role in the filtration of toxins, electrolytes, proteins, sugar, water and many other components found in the blood. A Nephron is made up of the kidney corpuscle and the kidney tubules. While the former are located in the cortex, most of the tubules are located in the renal medulla.

The The function of the renal cortex is to produce primary urine and serves the up the blood of toxic substances. Every day around 180 liters of primary urine are formed in the kidney corpuscles of the cortex, which then flows through the kidney tubules and is further concentrated. The blood vessels in the kidney corpuscles produce around 125 milliliters every minute.

Function of the kidney corpuscles

The functional units the renal cortex are around a million nephrons, which in turn consist of the Kidney corpuscles (Renal corpusculum) and Renal tubules (Renal tubule) are constructed. The formation of the primary urine takes place in the kidney corpuscles. Here the blood flows through a tangle of vessels, the Glomerulum, which is from the so-called. Bowman capsule is surrounded. The vessels of the glomerulum have the smallest Pores for the filtration of toxic substances. But it is not just a matter of openings, but a sophisticated filter system. The components of the blood are separated according to size and charge. Substances up to 100 nm can pass through the pores. In addition, the cells lining the vessels carry negative charges, which means that molecules of the same polarity are repelled. As a result of these two selection mechanisms, red and white blood cells as well as blood proteins remain in the capillaries. Other substances such as water, electrolytes, urea, sugar and small protein molecules pass through the pores and into the kidney tubules.

Function of the renal pelvis

The renal pelvis, Pelvis renalis, form the transition from the kidney calyx to the ureter, the so-called ureter. It fulfills the function of a collecting basin through which the urine is directed towards the urinary bladder. Since the renal pelvis and calyx represent a functional unit, one also speaks of the renal pelvis system. Together with the ureters, the bladder and the urethra (urethra) it is assigned to the urinary system.

The renal pelvis is located in the middle of the renal medulla. The funnel-shaped extensions towards the medulla form the calyxes of the kidneys, while the constrictions on the opposite side merge into the ureters.

The renal pelvis collects the urine produced in the cortex and marrow. Rhythmically contracting muscles enable urine to be transported from the calyx towards the pelvis and further into the ureters.

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Function of the renal tubules

The primary urine from the kidney corpuscles flows into the one made up of the kidney tubules Tubular systemwhere most of the water is reabsorbed and a wide variety of substances are released or also absorbed. This is how the actual urine is produced. The tubular system is off four main sections built up. Each of these sections fulfills different transport functions. The subdivision is made into Proximal tubule (Main piece), the so-called Henle loop, the Distal tubule (Middle piece) and the manifold. The main part is located together with the kidney corpuscles in the renal cortex, while the other parts are mainly to be found in the renal medulla.

The proximal tubule has a high permeability and thus enables one lively transport between cells. Above all, sodium ions, sugar molecules, bicarbonate and amino acids are reabsorbed here, i.e. removed from the primary urine and fed back into the bloodstream. Uric acid is also absorbed or released.

In the introductory section, the so-called Henle loop, the urine is increasing concentrated. It runs in the direction of the renal medulla and then curves in the opposite direction to the renal cortex. The Henle loop is used to absorb water.

The Distal tubule begins in the renal medulla and runs into the renal cortex before flowing into the collecting tube. In the even part, the Pars recta, the urine becomes more concentrated. Sodium ions are actively transported across the tubular wall. Water and chloride ions follow passively.

In the meandering Pars convoluta the water is not absorbed by means of a transporter, but hormone-dependent. That in the Adrenal gland formed steroid hormone Aldosterone is responsible for this.

A.DH (antidiuretic hormone) takes care of in the last section, the Manifold, for a regulation of the water balance. If necessary, it leads to the installation of small pores, so-called aquaporins, through which the Water resumed becomes.

Function of the calyxes

The Calyxes, Calices renalis, together with the renal pelvis, form a functional unit and belong to the first section of the urinary pathways at. The renal pelvis calyx system is used to transport the urine produced in the direction of the ureter.

The kidney papillae are part of the medullary pyramids and protrude into the calyxes. They have small openings at their tips through which the urine coming from the tubular system drips into the kidney calyx. Up to three papillae are surrounded by a small kidney calyx. The ten or so small goblets, in turn, unite. Two of them form a larger cavity, a large calyx, and finally end in the renal pelvis. Not every cup system has the same structure. In some cases the small calyxes open directly into a cavity, in others the calyx system has a tree-like structure with branches.

The role of the kidneys in regulating the water balance

One of the most important functions of the kidney is the regulation of the water balance. The largest part of the human body consists of water, the exact amount of which is subject to fluctuations depending on needs and consumption. The entire metabolic processes in the body are dependent on body fluids. In this way, the conversion and transport of a wide variety of substances is guaranteed. The kidney regulates the water balance.

The regulation is based on different mechanisms in the tubular system. The Water reabsorption on the one hand follows the osmotic principle of action. Special transport systems first transport ions from the canals across the wall. This creates an osmotic gradient. The water then passively follows the ions.

Another mechanism relies on one hormone-dependent principle. Here play in the Hypothalamus (Part of the diencephalon) produced ADH (Adiuretin, antidiuretic hormone) and the adrenal cortex hormone Aldosterone an important role.

Low blood pressure as a result of water loss causes a ADH distribution. The Urine becomes concentrated through increased reuptake of water. This is the case, for example, after vomiting or sweating. On the other hand, high blood pressure inhibits the release of ADH. This can result from drinking, alcohol or nicotine consumption, for example.

Also Aldosterone leads, via an increase in the resorption of sodium ions, to increased reabsorption of water, which osmotically follows the sodium. Aldosterone is made in the adrenal gland and its production is via the so-called Renin-Angiotensin-Aldosterone System (RAAS) regulated.

The influence of alcohol on the kidneys

The biggest part of ingested alcohol broken down into acetaldehyde in the liver. A smaller part around a tenth, is excreted via the kidneys and lungs. If alcohol is consumed in moderation, it does not pose a risk to the kidneys. Excessive alcohol consumption, on the other hand, damages the kidneys and their function permanently. The limit for Men is around 24 grams of alcohol per dayG. At Women one speaks already at 12 grams of alcohol per day of a critical amount.

Alcohol has a cell-damaging (toxic) Effect that, among other things, damages the cells of the kidney. In addition, urine excretion is favored. The body loses more water and can dry out (dehydrate).

People with a impaired kidney function should when consuming alcohol special caution let go. The cytotoxin remains in the body longer as a result of the reduced filtration capacity and, in addition to increasing its effectiveness, can cause the kidney disease to progress. In the worst case, one results acute kidney failure with complete collapse of kidney function.

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