The main function of the kidneys in the body lies in their anatomical and physiological characteristics

Among such organs as the heart and lungs, the kidneys seem to have a secondary role. Nevertheless, the main function of the kidneys in the body is to ensure its life in the most direct way.

Anatomy of the kidneys

Kidneys are the central organs of the excretory system of the body. But unlike the heart and lungs, they are less protected.

Kidneys are twin bean-shaped organs. They are located on each side of the vertebral column in the region of the lower thoracic( 11-12) and the upper lumbar( 1-2) vertebrae. Accordingly, their only bone defense is the two lower ribs. But this does not diminish the fact of their importance.

The average parameters of the kidneys are as follows:

Length from 11 to 12 centimeters.
The width varies between 5 and 6 centimeters.
The thickness of each organ does not exceed 4 centimeters. In most cases, the thickness of the kidney is 3.5-3.8 centimeters.
The mass of one kidney is not more than 200 grams. Weight fluctuations are allowed from 110 to 200 grams. And the left may be somewhat heavier than the right.

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The shape of the kidney is reminiscent of the fruit of the bean. Their convex side is facing away from the spine. The concave side "looks" at the sides of the spinal column. In the area of this concave side is the so-called renal sinus. It includes a renal artery. And out of it come the ureter and the renal vein.

Internal structure of the kidneys. Histology

Each kidney is a heterogeneous parenchymal organ. The latter means that it consists entirely of relatively dense tissue without any cavities. The only "voids" are in the area of the sine. But first things first.

The kidney consists of the following formations:

Connective tissue capsule. Thin and dense film of collagen( the main protein of connective tissue), almost completely covering the organ. In the area of the renal sinus, the capsule passes into the outer membrane of the ureter. Here, the capsule forms openings for the renal arteries and veins.
Cortical substance. It is located directly under the capsule, and also has "processes" directed towards the center of the organ. This substance contains nephrons - renal glomeruli. They are the basis of the functioning of the body. Without them, excretory function of the kidneys is impossible."Scions" in its composition contain arteries, veins and lymphatic vessels.
Brain substance. To be under the cortical. It is lighter than it, and in shape resembles a pyramid. Hence their second name is the "kidney pyramids".Each of them is turned with a base to the cortical substance, and the tip is directed towards the sinus. Pyramids are almost entirely composed of tubules of nephrons.
Kidney calyx. Hollow formations into which the tails of the parimide pass
Renal pelvis. The cavity in which the cups open, on the one hand, and the ureter, on the other.

Basic functions of the kidneys

This is important! The kidneys have 6 main functions: the isolation, regulation of blood pressure( due to the normalization of the oncotic properties of the plasma), the regulation of the ionic composition of the blood, participation in the general metabolism, the production of certain hormones of internal activity( endocrine) and hematopoietic.

Historically, the excretory function of the kidneys is the leading one. But due to the complex structure of the human body and the close interconnection of all organs and systems, the allocation of some main function is a bit wrong. In addition, all these properties of the kidneys are inextricably linked. Of course, the weakening of certain functions( endocrine and hematopoietic) at first does not affect others. But then, anyway, it will make itself felt.

Nephron

This is important! In order to understand how all the functions of the kidneys are interrelated, one must know the basics of the organ's work. And the main functional unit of the organ is the nephron.

Nephron consists of the following components:

Vessels. They are two, bringing( artery) and enduring( vein).
.Dense branching of these vessels. Bring the vessel to divide several times into small arterioles, which form a vascular glomerulus. It consists of venules( small veins), which are the continuation of arterioles. Venules are collected in one larger vessel, and it is called vyonyaschim. This vessel comes out of the glomerulus.
Capsule of Bowman-Shumlyansky. It represents a cluster of special functional cells( they are called podocytes) that surround the vascular glomerulus in the form of a flank. Where the top "glass" is freely open. Through it enter and exit the vessels. The leg of the "glass" is the beginning of the tubule. Violation of the excretory function of the kidney is largely due to the production of cells of this "glass".

Kidney function

The basics of kidney function can be summarized as follows:

Blood from the delivering vessel enters the arterioles of the nephron.
All arterioles are surrounded by podocytes. Their processes penetrate into the vessels. And between the processes there are special membranes. The blood that passes through these membranes is filtered. Only blood cells and some protein molecules pass through it. They enter the venules and into the vascular vessel.
The filtered blood enters the renal tubule of the nephron. It is the so-called primary urine. This primary urine moves on.
Primary urine, moving along the renal tubule, undergoes reabsorption. This term means reverse suction. The fact is that the tubule represents a rather long "tube", densely surrounded by a venous network of vessels, which are the continuation of the vascular vessel. This "tube" goes from the nephron to the brain substance. Here it makes a loop( it is called the Henle loop) and rises back to the cortical substance. Then again, "down" and opens into the kidney cup. So that's it. Throughout the tubule from the primary urine, various electrolytes, carbohydrates and lipids are fed back into the bloodstream. There remains only a small amount of plasma, with urea dissolved in it, creatine, uric acid, indole, urobilin( it gives the urine a yellow color), "excess" electrolytes and some other substances. All this is secondary urine.
Secondary urine enters the calyx. From there, it accumulates in the pelvis and is excreted into the ureter.

So in brief, there is a separation of the products of metabolism. But apart from their excretion, simultaneously, the kidneys perform other functions. They are closely associated with the allocation and significantly affect it, even if not to say what is regulated. Therefore, it is difficult to say what function the kidneys perform in the first place. Consider the remaining functions in more detail.

In the nephron, in addition to the vascular glomerulus and podocytes, there is one more for a less important group of cells. These are cells of the juxtaglomerular apparatus. His cells are involved in the regulation of blood pressure in the most direct way. On the one hand, some cells synthesize renin, which through the activation of angiotensin helps to narrow the blood vessels. This increases the overall peripheral resistance of blood vessels and increases blood pressure. On the other hand, other cells, I develop angiotensinase. This enzyme inhibits the activity of angiotensin. The total peripheral resistance of blood vessels decreases and blood pressure decreases.

But the regulation of electrolyte concentration and the endocrine function are in close relationship. The regulation of the ionic composition of the plasma occurs due to the tubule cells and the Henley loop during ion reabsorption. If the number of some of them in the blood plasma exceeds the norm, their reabsorption decreases and vice versa. This is largely due to aldosterone - the hormone of the adrenal glands, regulate the secretion of kidney tubules through the production of local hormones.

Finally, the hematopoietic function of the kidneys is to produce erythropoietin, a potent stimulant of the red bone marrow. Here, the erythrocytes are formed and mature.

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