Glomerular fitration (urine formation) T2 W9

Glomerular filtration

Process in which high blood pressure forces fluids and solutes through a filtering membrane.

Where does glomerular filtration process occur

The process takes place in the renal corpuscle, as fluid moves from the glomerulus to the glomerular capsule.

What makes glomerular capillaries exceptionally permeable and why is it needed

They have many pores allowing for large amounts of fluid to pass from the blood into the glomerular capsule.

Glomerular capsule internal layer

Internal layer is made of epithelial cells that cling to the glomerular capillaries, forming a thin surface. The epithelial cells have openings that allow the filtered fluid from the blood to enter the capsular space insider the glomerular capsule. This fluid is now called a filtrate

Why does glomerulus have high blood pressure

• Promotes filtrate formation (hydrostatic pressure)

• The blood pressure in the glomerulus is very high due to the high-resistance to blood flow of the efferent arterioles, whose diameter is smaller than the afferent arteriole.

• As a result of this high blood pressure, filtration occurs along the entire length of each glomerular capillary and substances do not move back the other way into the blood.

What does the glomerulus allow to pass through

• All blood components except blood cells and plasma proteins.

• Smaller molecules pass freely from the blood into the glomerular capsule and form the filtrate: water, glucose, amino acids, salts (ions) and nitrogenous wastes (urea, uric acid, ammonium ions, creatinine).

• Therefore they’ve got similar concentration in blood and glomerular filtrate

How much filtrate is produced daily

180L

What does filtrate consist of

• Water

• Salts (ions)

• Small nutrient molecules (glucose and amino acids)

• Wastes like urea

• Uric acid

• Ammonium ions

• Creatinine

• Hormones

• Drugs.

Glomerular filtration rate (GFR)

The volume of filtrate formed each minute by the combined activity of all 2 million glomeruli of the kidneys.

What is glomerular directly proportional to

⚬Net filtration pressure: the blood pressure in the glomerulus

⚬Total surface area for filtration: glomerular capillaries have a huge surface area (collectively equal to the surface areas of the skin!).

⚬Filtration membrane permeability: glomerular capillaries are thousands of times more permeable than other capillaries due to their porous structure.

⚬Thin membrane surface of both the glomerulus and glomerular capsule.