Kidney is the organ of the body produce urine, most of the body of water, salts and organic compounds are eliminated from the body through the urine, the urine formation in the human body for the maintenance of the environment is vital.
The formation of urine: the formation of urine through the main glomerular filtration, tubular and collecting duct reabsorption, and renal collecting duct secretion, excretion process of the three in a row.
The glomerular filtration: the cycle of blood flow glomerular capillaries, plasma water and small solute molecules, including a small number of smaller molecular weight plasma protein through the kidney filtration membrane filter to the small capsule of the formation of intracavitary Ultrafiltrate (original urine), and this is the role of the so-called glomerular filtration.
Glomerular filtration role in the decision of the three main factors:
(1) filtration membrane filtration is the permeability of the structure of the foundation. Is the glomerular filtration membrane of the blood capillaries and small kidney capsule more than every other mode between the filtrate, mainly by the endothelial cells, non-cell-based film and the renal capsule of visceral epithelial cells Cheng, both to prevent membrane filtration macromolecular material filter out the mechanical barrier, and prevent the filter material with a negative charge of static electricity barrier. As a result, the kidney filtration through the membrane, not only filter the water liquid form of the original urine can be retained in the body of useful material at the same time, the body's waste discharges.
(2) effective filtration pressure is the driving force for filtration. Effective filtration pressure by the strength of 3: 1, 0000 glomerular capillary pressure, which is to promote the power of the filter. 2, 0000 plasma colloid osmotic pressure, it is to stop the plasma filter out the power of water. 3, 0000 intracapsular pressure, it is against the power of the filter. Effective pressure = glomerular filtration pressure - (plasma colloid osmotic pressure Capsule +). Where can affect the glomerular capillary pressure, or plasma colloid osmotic pressure of the capsule, can make changes in glomerular filtration pressure, thus affecting the glomerular filtration rate.
(3) renal plasma flow filtration is the premise and basis of the material. Renal plasma flow and glomerular filtration rate in direct proportion to, when the renal plasma flow increased, the human form of urine also increased.
Tubular and collecting duct of the re-absorption: When the original flow through tubular, the occurrence of re-absorption, the original of all the glucose in urine, most of the water and inorganic salts were part of the tubular re-absorption and into the enveloping the tubular Outside the capillaries, to send back to the blood. The remaining part of the water, and inorganic waste such as urea on the formation of urine outflow from the tubular.
And the impact of renal collecting duct reabsorption of factors:
(1) tubule fluid in the concentration of solutes. Tubule solute in liquid form by the osmotic pressure, is tubular and collecting duct water absorption of force against. If the small tube of liquid solute in high concentrations, the osmotic pressure to form a large, tubular reabsorption of water against the force, the results can increase urine, which is called osmotic diuretic.
(2) glomerular filtration rate. Proximal tubule reabsorption per minute ml of liquid filtration, said the rate of tubular reabsorption, and glomerular filtration rate to maintain a balance between, known as the Tube strike a balance. Its physiological significance is the end result of urine will not increase or decrease in glomerular filtration rate and drastic changes.
(3) renal tubular epithelial cells. Tubular epithelial cells have a strong re-absorption, and selective, when some of the parameters of the function of cells, renal tubular injury may be caused by the re-absorption of obstacles, leading to increase in the volume of urine or appear in some unusual ingredients.
Tubular and collecting duct secretion, excretion: renal collecting duct and the secretion that the tubular and collecting duct epithelial cells, through its own metabolism resulting from the material released into the fluid in the tubules. Excretory functions, it means tubular epithelial cells in the blood of the Central Plains have some of the material into the small tube of liquid. In the process of renal excretion of H ion secretion, NH3, K ion, and through the exchange of sodium and sodium hydrogen exchange, retains sodium, in addition to the body produced by normal creatinine and uric acid, such as Ma-on, not only from the glomerular Filtration, but also by renal tubular excretion into the body of certain substances, such as penicillin, phenol red, and so on through the excretion of the proximal tubules, lumen into small, and then eliminated from the body of.
When the formation of urine, renal kidney in millions of units of the formation of urine in the pool pelvis, ureter, after the transport, storage for the time being, in the bladder.
The formation of urine is a continuous, discharge of urine is the interval. When the bladder urine of bladder, a certain amount of storage, the pressure on the bladder wall, intended to produce urine. Urination, the bladder muscle contraction, the urethral sphincter to relax, urine from the bladder outflow through the urethra eliminated from the body.