Question

Question 3

In order for blood to flow from the veins back into the heart, the pressure in the right atrium must be lower than the pressure in the veins. Two physiological pumps help increase pressure in the venous system.

1. How do pressure differentials that allows for inflation and deflation of the lungs also assist in venous return?
2. Explain why individuals experience edema in their lower extremities during the course of a long distance flight.

Answer 1

Two physiological pump which aid venous retrun are

a)skeletal muscle pump

Pheripheral muscles in the thigh and calf act as a peripheral heart.

when the muscles in the thigh and calfs contract it act pressure over the valves and open the valve which help to drain blood from the superficial vein to deep vein and increases the venous return

b)Respiratory pump

respiratory pump is also a important factor which regulate the venous return.

During inspiration venous return increases and during expiration venous return decreases.

2)During inflation,the intrathoracic volume is increased thereby the intrathoracic pressure is decreased.

Venous return is increased when the pressure in the right atrium is decreased.when the intra thoracic pressure decreases during inspiration the pressure exerted over the right atrium also decreases.so that the flow of blood from the periphery to the heart is increased

During expiration the intra thoracic pressure is higher than the atmospheric pressure,it exert pressure over the right atrium so that the blood flow into the heart is decreased.

3)long distance flight travellers experience edema in the lower extremities because the person is sitting for a long period that time there will be pooling of blood in the lower extremeties.The skeletal muscle pump will be inactive and there will be decreased venous return .almost a large portion of the blood will be pooled n the lower extremities.it result in the increase of hydrostatic pressure in the cappilaries .there will be increased filtration of fluid into the tissue space causing edema.