The human urinary system performs the function of removing toxins, unnecessary, harmful compounds, while maintaining the necessary amount of mineral salts and water in the body. This task is realized through the formation of urine in the kidneys in a certain volume and with a certain concentration.
The structure of the urinary system.
Its structure includes organs that produce urine (kidneys), accumulate and remove urine from the body (bladder, urethra, ureters).
The kidneys located in the space behind the peritoneum on both sides of the spine are shaped like beans. The left kidney is slightly higher than the right. The upper edges of this paired organ are close to the spine, the lower ones are distant.
In the kidney, the lower and upper pole, the inner and outer edges are determined. In the center of the inner edge are the gates (recess). Through them, the nerves and artery enter the organ, the ureter, lymph vessels, and vein exit. The combination of these elements forms the renal pedicle.
A fat capsule, its own membrane, and connective tissue fascia surround each kidney. Two layers enter the substance of the kidney - the cerebral and cortical. The first is represented by twelve to fifteen formations in the shape of a cone. They are called pyramids. Cortical matter seeps between nearby pyramids. The cortical layer has a thickness of four to thirteen millimeters.
The urinary system has several regulatory mechanisms.
The amount of water in the body affects the concentration of urine. Excessive water volume inhibits the release of antidiuretic hormone (ADH) in the pituitary gland , which controls the absorption of salts and water. With a lack of water, sensitive special formations (osmoreceptors) are excited. In this case, ADH is released into the bloodstream, which contributes to the reabsorption (reverse absorption) of water.
The urinary system, together with urine, excretes water, salt, uric acid, and urea. These components are isolated through the lungs, skin, intestines, salivary glands, however, they are not able to replace the kidneys.
The formation of urine, including the stage of filtering fluid from the blood, secretion and reverse absorption, is carried out in nephrons (component parts of the kidney tissue). In each nephron there are renal (Malpighian) bodies, which provide the filtration process, and urinary tubules. The body is represented by a hemispherical double-walled bowl. The gap between its walls covers a capillary glomerulus. A tubule also comes out of the gap.
Intravascular pressure (70-90 mmHg) promotes the leakage of the liquid part of the blood into the nephron capsule. This process is called filtration, the leaked fluid, respectively, is called "filtrate" (primary urine).
The urinary system forms a filtrate, consisting mainly of water. The concentration of low molecular weight substances in primary urine is approximately the same as in plasma. With the advancement of the filtrate through the tubules, its composition is constantly changing, as a result, it becomes the final urine. The average urine volume is about one and a half liters per day.
The urinary system also includes the bladder in its structure. This organ performs the function of accumulating urine. A powerful membrane of the muscles is located in the wall of the organ. With its reduction, the volume of the cavity of the bubble decreases. In the area of the openings of the ureters, the internal opening of the urethra are sphincters (compressors). They regulate urine flow.
To the bottom of the bladder fit tubules (ureters).
Excretion of urine is carried out through the urethra, leaving the bladder.