Capillary and Venous Blood Pressure (Nursing)

00:01 So our capillary blood pressure is going to be much lower than arterial blood pressure.

00:07 It's going to range from 35 mm Hg at the beginning of the capillary bed to 17 mm Hg at the end of the capillary bed.

00:18 Below capillary pressure is desirable, because if the pressure was too high, it would rupture the very fragile and thin-walled capillaries.

00:29 Most of our capillaries are also very permeable, so a high pressure would force the filtrate in the capillary to leak out into our interstitial spaces.

00:40 So now moving on to our veins.

00:43 The venous blood pressure is going to change very little during the cardiac cycle.

00:49 There is a small pressure gradient of only about 15 mm Hg.

00:54 So, if a vein is cut, the low pressure of the venous system is going to cause the blood to flow out nice and smoothly.

01:03 This is in contrast when an artery is cut.

01:06 In this case, blood is going to spurt out because the artery system is a much higher pressure system.

01:14 The low pressure in our veins is due to the cumulative effects of peripheral resistance, The energy of the blood pressure is lost as heat during each circuit.

01:25 And the low pressure of the venous side requires adaptations in order to help the venous blood return to the heart.

01:35 The factors that we use to aid venous return include the muscular pump, where the contraction of our skeletal muscles milk the blood back toward the heart.

01:47 At the same time, valves present within our veins are going to prevent backflow of the blood so that is constantly moving up and not going backwards.

01:58 We also have a respiratory pump.

02:01 Where pressure changes during the breathing, move our blood toward the heart by squeezing our abdominal veins and our thoracic veins as they expand.

02:12 Finally, we have sympathetic vinoconstriction, we're under sympathetic control, the smooth muscles are going to constrict and push blood back toward the heart.

02:25 So depicted is the milking action of the skeletal muscles that's going to propel the venous blood from the lower extremities toward the heart.