In the human body as a result of biochemical formed oxidation decomposition products: water, carbon dioxide, nitrogen, salts of phosphorus and other substances.
Carbon dioxide and water vapor in the lungs are removed during respiration and liquid decomposition products - mainly by the kidneys and sweat glands partially.
Excess of these materials gives homeostasis and therefore harmful for the organism.
By allocating organs include the lungs, skin and kidneys. In this case the kidneys, ureters, bladder and urethra, urination engaged, play a major role. The main function of the excretory organs - maintain a constant internal environment.
Blood enters the kidney at the renal arteries. Here she is cleared of unnecessary substances and is returned to the blood flow in the renal veins. Filtered kidneys harmful substances form urine, which is under the ureters into the bladder. At the time of urination circular muscle (sphincter), closing access to the urethra relaxes the bladder wall are reduced, the urine is expelled out.
The kidney - a pair of purplish-brown body. The concave part facing the spine is called the gateway to the kidneys. Incoming them renal artery carries blood crude. Get out of the gate kidney renal vein and ureter. According veins "clean" the blood is coming into the bladder into the inferior vena cava of the systemic circulation, and through the ureter released products of decomposition.
Kidney consists of an outer cortex andinner medulla. Last differentiated into renal pyramid, adjacent to the base of the cortex, and the tops directed to the renal pelvis. The renal pelvis is a reservoir that collects the urine until it is released into the ureter.
Microscopic structural and functionalunit of the kidney is the nephron. In each kidney there are about a million, and it is in their blood plasma is filtered. Nephron consists of a capsule, passing in a long convoluted tubule. Capsules and the initial part of the tubules are located in the cortex of the kidney, and their continuation - in the medulla.
Blood plasma penetrates through the thin portionsblood vessel wall in slit nephron capsule. Corpuscles (erythrocytes, leucocytes, platelets) and proteins remain in the arterioles. The tubule nephron fall decomposition products, water and nutrients. Together, they constitute the primary urine. Per day produces about 150 liters of primary urine and whole blood (5 liters average) passes through the kidneys approximately 300 times.
Along convoluted tubule primary urinemoving on. There occurs in the blood reabsorption relevant substances and most of the water, and in the body are unnecessary canaliculus "waste". This forms a secondary, final urine - a concentrated solution of urea and oxalic salts, uric, phosphoric acid and other acids. For convoluted tubules follow collective directing fluid into the renal pelvis. The day produced 1.5-2 liters of secondary urine.