Glomerular filtration and filtration 5, glomerular filtration

When circulating blood passes through the glomerular capillaries, the water and small molecule solutes in the plasma, including a small amount of plasma proteins with small molecular weight, can be filtered into the cyst cavity of the renal sac to form a filtrate. In the micropuncture method, a microglass with an outer diameter of 6-10 m is inserted into the cyst cavity of the renal corpuscle using a micromanipulator. Paraffin oil is injected into the proximal bulbular tubules where the cyst meets the cavity to prevent filtrate from entering the renal tubules.

The liquid directly into the capsule cavity is auctioned with a microglass tube for microchemical analysis (Figure 8-2). The analysis showed that, in addition to the very little protein content, the concentrations of various crystalline substances such as glucose, chloride, inorganic phosphate, urea, uric acid and creatinine were very close to those in plasma, and the osmotic pressure and pH were also similar to those of plasma, thus proving that the capsule fluid was indeed the ultrafiltrate of plasma. The amount of ultrafiltrate produced by the two kidneys per unit of time (per minute) is called glomerular filtration rate (GFR).

According to the measurement, the glomerular filtration rate of the body surface area is about 125ml min. According to this calculation, the total amount of plasma filtered out of the glomeruli by both kidneys per day and night will be as high as 180L. This value is about 3 times the body weight.

The ratio of glomerular filtration rate to renal plasma flow is called fraction filtration. It was calculated that the renal plasma flow was 660ml min, so the filtration fraction was: 125 660 100 = 19%.

The filtration fraction showed that about 1 5 mantles of the plasma flowing through the kidney had globules into the cyst cavity. The size of the glomerular filtration rate is determined by the filtration coefficient (kfr).

1.Glomerular filtration produces raw urine.

2.Reabsorption of renal tubules and collecting ducts.

3.Secretion and excretion of renal tubules and collecting ducts.

When blood passes through the kidneys, because the kidneys are made up of nephrons. Nephrons also include glomeruli, renal sacs, and renal tubules. When passing through the glomeruli, a large molecule of glucose.

Blood cells cannot be filtered. However, other small molecules of nutrients are sieved into the renal sac, and then the renal tubules reabsorb the other nutrients, and other waste products are excreted with water. As blood passes through the kidneys, urea, uric acid, and excess sodium decrease.

If the permeability of the glomerular filtration membrane is impaired, it will lead to the leakage of protein occult blood, etc., and the urine test will be positive, which is usually negative.

The action is to block proteins.

The filtration barrier consisting of a three-layer structure of endothelial cells, basal membrane, and hiatal membrane of renal cystopocytes in the glomerular capillary wall is called a filtration membrane. The glomerular filtration membrane has a three-layer structure, from the inside to the outside: endothelial cells, basement membrane, and visceral epithelial cells (podocytes) of the glomerular sac.

There are small pores between endothelial cells, about 500 to 1,000 aSmall solutes and water easily pass through such small pores.

The basement membrane is a continuous and non-porous dense structure with a thickness of 3200 3400A, and the surface is covered with a gelatinous substance, which seems to be dominated by mucopolysaccharides and has a negative charge.

CG-GFR formula:

1. Male CCR = (140-age) Weight (kg) Serum creatinine (umol L).

Female CCR=(140-age) weight (kg) serum creatinine (UMOL L) or male CCR=[(140-age) weight (kg)] serum creatinine (UMOL L)].

2. Calculation results for women 2. Simplify the calculation formula for MRDR:

EGFR = (186 SCR) - (age) if female.

c-agfr = (186 scr) - (age) if female Chinese corrected).

SCR is serum creatinine (mg DL), and the unit conversion of serum creatinine: 1mg DL = umol L

The normal value of EGFR is 80-120ml min, and GFR is the glomerular prefiltration rate, which is a more accurate clinical indicator of glomerular function. EGFR is a calculated glomerular filtration rate (GLF) that is calculated by checking blood and urine creatinine values.

The determination of EGFR is interfered by factors such as age, gender, weight and drugs, the EGFR value is generally higher than that of women, and the young are higher than the elderly, with the increase of age, the EGFR value has a natural downward trend, the EGFR increases significantly during pregnancy, and returns to normal after childbirth, and some drugs such as diuretic cimetidine can interfere with the results, so it is necessary to objectively evaluate the value of the amount of jujube in combination with the specific situation.

The glomeruli is composed of arterioles that extend into the balloon and branch hollowed out into the base of the capillary lobules of 4 to 8 japonics. The arterioles that enter the balloon form the balloon artery, and form capillary loops through branches at all levels, and each loop is lobulated, called capillary lobes. The capillaries of each lobule converge into a single out-of-globular arteriole, which leaves the glomerulus from the pole of the vessel.

There are a small number of mesangial cells and stroma between the glomerular capillary loops, which play a supporting role in the capillary loops, and have the effect of constricting and dilating the capillaries, regulating the blood flow of the capillaries, and also phagocytosing the deposits on the capillary basal membrane to maintain the permeability of the basal membrane. The wall of the capillary loop is where the kidneys filter blood, called the filtration membrane.

1) Selective filtering of the size of the molecule: The three-layer structure of the filtration membrane has small pores of different sizes, and only material molecules smaller than its pore size can pass freely.

2) Selective filtration of molecular charges: Each layer of the filter membrane contains many negatively charged substances, mainly glycoproteins. They limit the filtration of negatively charged plasma proteins.

The decrease in effective glomerular filtration pressure is:

Glomerular effective filtration pressure = glomerular capillary blood pressure - (glomerular balloon pressure + plasma colloidal osmolality). A decrease in effective filtration pressure can lead to a decrease in glomerular filtration rate.

The relevance is as follows. When massive blood loss, dehydration, etc., cause hypovolemia or decrease in the mean arterial pressure throughout the body, the glomerular capillary blood pressure decreases, which can lead to a decrease in the effective glomerular filtration pressure; The relative relaxation of the introverter and the outgoing arteriole directly affects the capillary blood pressure in the glomerulus, and also causes changes in the effective glomerular filtration pressure and glomerular filtration rate.

The intraglomerular pressure is generally constant, but when urinary tract obstruction, tubular obstruction, and renal interstitial edema compress the renal tubules, the intraglomerular pressure increases, thereby reducing the effective filtration pressure and reducing the glomerular filtration rate. In general, the change of plasma gel vertical early body osmolality has no obvious effect on the effective glomerular filtration pressure.

The glomerular filtration area is reduced, and the kidney has a large compensatory reserve, and after removing one kidney, the glomerular filtration area is reduced by 50%, and the healthy kidney can still compensate for its function. However, when chronic nephritis progresses, a large number of nephrons are destroyed and the glomerular filtration area is extremely reduced, which can reduce the glomerular filtration rate and cause renal failure.