Net Filtration Pressure (NFP) – Urine Formation (Nursing)

00:01 Forces that promote the filtrate formation include three different forces.

00:06 First, we have the hydrostatic pressure that's found in the glomerular capillaries.

00:12 This is essentially the glomerular blood pressure.

00:17 This is the chief force that is pushing the water and solute out of the blood into the glomerulus.

00:24 The pressure is actually quite high at 55 millimeters of mercury.

00:30 This is compared to the lower 26 millimeters of mercury that you seen in most other capillary beds in the body.

00:39 The reason why the hydrostatic pressure is so high is because the efferent arteriole has a high resistance with a smaller diameter than the afferent arteriole.

00:52 This causes the plasma to pull in the glomerular capillaries, which increases the hydrostatic pressure.

01:01 While hydrostatic pressure is higher than normal and are glomerular capillaries to other pressures caused fluid to remain in the capillaries and not filter out.

01:14 These include the hydrostatic pressure and the glomerular capsule.

01:20 The filtrate pressure and this capsule is 15 millimeters of mercury.

01:25 And this pressure is going to push back up against the glomerular capillaries.

01:32 The third pressure is our colloid osmotic pressure or the pull from most proteins that remain in the blood.

01:42 The colloid osmotic pressure is 30 millimeters of mercury.

01:48 So if we put all of them together, we get our net filtration pressure.

01:55 So this is going to include our 55 millimeter mercury forcing out from our hydrostatic pressure of the glomerular capillaries - the 45 millimeters of mercury opposing or pushing in from our colloid osmotic pressure and our hydrostatic pressure of the glomerular capsule.

02:19 This pressure or the net filtration pressure is going to be responsible for the formation of our field trip.

02:28 And this is the main controllable factor that determines our glomerular filtration rate or GFR.