The changes in any of the three factors that affect the effective filtration pressure can affect the effective filtration pressure, thereby affecting the glomerular filtration rate.
Experiments prove that the change of glomerular capillary blood pressure, blood pressure in the arteries of 10.7 ~ 24.0kPa (80 ~ 180mmHg) range, renal blood flow autoregulation has remained relatively stable, no significant changes in glomerular capillary pressure. A self regulatory mechanism, the majority of people believe that the increase in arterial blood pressure, vascular smooth muscle afferent by stretch and contraction, blood flow resistance increases, the blood flow of the glomerular capillary is not caused by increased blood pressure is not increased, and no significant changes in effective filtration pressure and glomerular filtration rate; when the arterial blood pressure decreased the goal, arterial wall diastolic blood flow resistance decreases, the blood flow of the glomerular capillary is not reduced, the blood pressure is not reduced, and no obvious change of effective filtration pressure and glomerular filtration rate. This shows that the regulation of glomerular filtration function is realized through the regulation of renal blood flow, in order to ensure the normal functioning of the body in the physiological state of urine. But if the arterial blood pressure decreased to 10.7kPa (80mmHg) below (such as bleeding), beyond the autoregulation of renal blood flow, glomerular capillary pressure will decrease, reduce the effective filtration pressure, glomerular filtration rate decreased when oliguria, arterial blood pressure dropped to 5.3 ~ 6.7kPa (40 ~ 50mmHg). Can cause urine. In the advanced stage of hypertension, due to the narrow nature of the lesion of the arterial generator, it can also reduce the blood pressure of the glomerular capillaries, and cause the decrease of glomerular filtration rate, resulting in oliguria and even urine.
Factors affecting glomerular filtration rate.Changes in plasma colloid osmotic pressure in human plasma colloid osmotic pressure in normal circumstances does not appear significant fluctuations. Only when the plasma protein concentration decreased, the plasma colloid osmotic pressure decreased, so that the effective filtration pressure and filtration rate increased, and the urine volume increased. For example, the main reason for the increase in urine volume caused by intravenous infusion of a large amount of physiological saline is the dilution of plasma protein, the decrease of plasma protein concentration and the decrease of plasma colloid osmotic pressure.
The change of renal capsule pressure is stable under normal circumstances. When the occurrence of urinary tract obstruction, such as renal pelvis stones, ureteral stones or tumor oppression, can cause increased pressure on the affected side of the capsule, so that the effective filtration pressure, filtration rate decreased. In addition, some drugs, such as some sulfanilamide, easy in tubular fluid in the acidic environment of crystallization break out, excessive hemolysis of the filtrate to hemoglobin containing or certain diseases, the drug can block the renal tubular crystals or hemoglobin caused by pressure increased, leading to glomerular filtration rate and effective filtration pressure drop.
As the plasma colloid osmotic pressure gradually increased, the effective filtration pressure decreased. The rate of increase of the plasma colloid osmotic pressure must affect the speed of the decrease of the effective filtration pressure. The increase of plasma colloid osmotic pressure is closely related to glomerular plasma flow. When the plasma flow increased, the colloid osmotic pressure rises slowly, effective filtration pressure decline rate will slow down, the effective length of glomerular filtrate formation prolonged, filtration rate increases; on the contrary, glomerular plasma flow decreases, the effective length of glomerular filtrate formation shortened, filtration rate decreased. Self regulation under normal circumstances because of renal blood flow, glomerular plasma flow remained relatively stable, only in the human body for strenuous exercise or in large blood loss, severe hypoxia and other pathological conditions, due to enhanced sympathetic nerve activity, renal vasoconstriction, the renal blood flow and glomerular plasma flow was significantly reduced, caused by glomerular filtration rate decreased.
The size of the permeability of the glomerular filtration membrane can be measured by the molecular weight of the material it allows. The plasma of small molecular substances easily through the filtration membrane pore sizes; but large molecules, such as molecular weight of plasma albumin 69000 is difficult to pass, but also the existence of selective sialoprotein blocking effect, and its concentration in the filtrate in the plasma concentration of not more than 0.2%; the molecular weight of more than 69000 of the immunoglobulin. Fibrinogen cannot through filtration membrane. In addition, hemoglobin, which has a molecular weight of 64000, can be filtered, but it is present in the form of a complex that binds to the globin, and thus cannot be passed. When there is a large number of hemolysis, the hemoglobin content in the blood is more than the amount of haptoglobin, when not combined with globin hemoglobin can be filtered out of the urine, the formation of hemoglobinuria.
Under normal circumstances, the permeability of the filtration membrane is stable, only in the pathological changes and the influence of the composition of urine. Such as glomerular inflammation or hypoxia, often accompanied by proteinuria. In the past, it was believed that this was caused by increased permeability of the membrane. In recent years, it has been found that the permeability of filtration membrane is reduced, not increased. Albuminuria is due to lesions of the filtration membrane on the negatively charged saliva protein decreased or disappeared, weakening of the same charge repulsion of the negatively charged albumin, albumin filtration due to easy to make. When the lesion causes damage to the filter membrane, red blood cells can also filter out the formation of hematuria.
factors affecting glomerular filtration rate.Glomerular filtration membrane total area of about 1.5 ~ 2m2. Under normal circumstances, all the glomeruli are in active state, so the filter area remains stable. Under pathological conditions, such as acute nephritis, glomerular capillary endothelial hyperplasia, swelling, swollen basement membrane thickened, causing capillary lumen stenosis or occlusion, resulting in the effective filtration area decreased, filtration rate decreased, appeared oliguria urine even without.
Beijing In China