Which forces affect net filtration pressure?

Sebastian Wright January 26th, 2026 at 12:30 PM

The net filtration pressure is determined by the balance of the Starling forces (the hydrostatic pressure and the oncotic pressure within the glomerular capillaries and Bowman's capsule).

Similarly, what is the force that causes filtration?

The Mechanisms of Filtration The force of hydrostatic pressure in the glomerulus (the force of pressure exerted from the pressure of the blood vessel itself) is the driving force that pushes filtrate out of the capillaries and into the slits in the nephron.

Similarly, what is Net filtration pressure? The net filtration pressure (NFP) represents the interaction of the hydrostatic and osmotic pressures, driving fluid out of the capillary. Since filtration is, by definition, the movement of fluid out of the capillary, when reabsorption is occurring, the NFP is a negative number.

Regarding this, what pressure is the major force of filtration in the glomerulus?

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One of these forces is called hydrostatic pressure. In the case of the kidney, hydrostatic pressure is the pressure exerted by fluid on the capillary walls of the glomerulus or the walls of the Bowman's capsule.

How does Net filtration pressure affect glomerular filtration rate?

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When blood pressure drops, the same capillaries relax to maintain blood flow and filtration rate. The net result is a relatively steady flow of blood into the glomerulus and a relatively steady filtration rate in spite of significant systemic blood pressure changes.

What forces promote net filtration and how?

The net filtration pressure (NFP) represents the interaction of the hydrostatic and osmotic pressures, driving fluid out of the capillary.

What factors affect filtration pressure?

The K_f is directly proportional to the surface area of the filtering membrane and its hydraulic conductivity. The net filtration pressure is determined by the balance of the Starling forces (the hydrostatic pressure and the oncotic pressure within the glomerular capillaries and Bowman's capsule).

What are the two major factors involved in filtration?

Hydrostatic pressure of glomerular capillaries.
Oncotic pressure of glomerular capillaries.
Hydrostatic pressure of Bowman's space.
Oncotic pressure of Bowman's space.

Where does filtration occur?

Filtration is the mass movement of water and solutes from plasma to the renal tubule that occurs in the renal corpuscle. About 20% of the plasma volume passing through the glomerulus at any given time is filtered. This means that about 180 liters of fluid are filtered by the kidneys every day.

What happens if GFR is too high?

If GFR is too low, metabolic wastes will not get filtered from the blood into the renal tubules. If GFR is too high, the absorptive capacity of salt and water by the renal tubules becomes overwhelmed.

What is effective filtration pressure?

The effective filtration pressure (EFP) is the total pressure that promotes filtration, is determine as follows: Glomerular blood hydrostatic pressure minus the colloidal osmotic pressure of blood and capsular hydrostatic pressure.

What force opposes glomerular filtration?

The forces that govern filtration in the glomerular capillaries are the same as any capillary bed. Capillary hydrostatic pressure (Pc) and Bowman's space oncotic pressure (πi) favor filtration into the tubule, and Bowman's space hydrostatic pressure (Pi) and capillary-oncotic pressure (πc) oppose filtration.

What are the 4 Starling forces?

The four Starling s forces are:

hydrostatic pressure in the capillary (Pc)
hydrostatic pressure in the interstitium (Pi)
oncotic pressure in the capillary (pc )
oncotic pressure in the interstitium (pi )

Where does most selective reabsorption occur?

It involves the reuptake of useful substances from the filtrate and occurs in the convoluted tubules (proximal and distal)
The majority of selective reabsorption occurs in the proximal convoluted tubule, which extends from the Bowman's capsule.

Where does hydrostatic pressure come from?

Hydrostatic pressure is the pressure that is exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above.

Why is it called ultrafiltration?

Due to the pressure, the liquid part of the blood which filters out from the glomerulus passes into the Bowman's capsule. This filtration under extraordinary force is called ultrafiltration. This filtrate is known as the glomerular filtrate.

Is urea filtered in the glomerulus?

Plasma Urea

With a molecular weight of 60 Da, urea is freely filtered at the glomerulus. However, it can be readily reabsorbed, and the amount of tubular reabsorption is variable. In states of actual or effective intravascular volume depletion, urea reabsorption can be substantial.

What two pressures oppose filtration and what are their values?

48 Cards in this Set

What force drives filtration at the glomerulus?	Blood pressure
Blood pressure in the glomerulus is about ___mmHg	60mmHg
What two pressures oppose filtration and what are their values?	Capsular hydrstatic pressure (15mmHg) Osmotic pressure of blood (28mmHg)
What is the normal net filtration pressure?	17mmHg

Is glomerular filtration passive or active?

Glomerular filtration removes solutes from the blood; it is the first step of urine formation. In tubular reabsoption, the second step of urine formation, almost all nutrients are reabsorbed in the renal tubule by active or passive transport.

What is blood osmotic pressure?

Osmotic pressure is a measure of the concentration of solutions. It does not cause actual, physical pressure. High osmotic pressure in the blood will cause water to be taken out of the cells. The kidneys usually maintain osmotic pressure under very tight control, so elevated osmotic pressure usually is abnormal.

What is capillary hydrostatic pressure?

Hydrostatic pressure is a force generated by the pressure of fluid on the capillary walls either by the blood plasma or interstitial fluid. The net filtration pressure is the balance of the four Starling forces and determines the net flow of fluid across the capillary membrane.

When the net filtration pressure is negative?

The net driving force (NDF) for fluid movement is the net pressure gradient determined by the sum of the individual hydrostatic and oncotic pressures, and is expressed in the units of mmHg. When the NDF is positive, there is net fluid filtration, and when it is negative, there is net fluid reabsorption.