venous return

Question 1

venous return

Answer 1

volume of blood returning back to the heart

Question 2

why are mechanisms needed to help venous return

Answer 2

• because the pressure in the veins is very low and this makes it difficult for blood to return back to the heart
• also the large lumen of the vein offers little resistance to blood flow

Question 3

what are the venous return mechanisms

Answer 3

1. the skeletal muscle pump
2. the respiratory pump
3. pocket valves

Question 4

what are other factors that aid venous return

Answer 4

• thin layer of smooth muscle in the walls of the veins. This helps squeeze blood back towards the heart
• gravity helps the blood return to the heart from the upper body
• the suction pump action of the heart

Question 5

the skeletal muscle pump

Answer 5

• when muscles contract and relax they change shape. This change in shape means that the muscles press on the nearby veins and cause a pumping effect and squeeze the blood towards the heart

Question 6

the respiratory pump

Answer 6

• when muscles contract and relax during breathing in and breathing out, pressure changes occur in the thoracic and abdominal cavities. These changes in pressure compress the nearby veins and assist in blood return to the heart

Question 7

pocket valves

Answer 7

it is important that blood in the veins only flows in one direction. Valves ensure that this happens. This is because once the blood has passed through the valves, they cost to prevent blood flowing back

Question 8

why do we need to do a cool down after exercise

Answer 8

to keep the skeletal muscle pump and respiratory pump working therefore preventing blood pooling (blood collecting in the veins)

Question 9

the impact of blood pressure on venous return

Answer 9

when there is an increase is systolic pressure venous return increases
when there is a decrease in systolic pressure venous return decreases

Question 10

impact of a pressure gradient between the right atrium and vena cava on venous return

Answer 10

• increase in venous pressure or decrease in right atrial pressure or a decrease in venous resistance = increase in venous return
• increase in right atrial pressure = decrease in venous return
• blood pressure in right atrium and peripheral veins is very low so that there is a pressure gradient driving venous return from the peripheral veins to the heart is also low
• because of this small changes of blood pressure in either the right atrium or peripheral vein can cause a large change in the pressure gradient and significantly affect the return of blood

Question 11

describe the relationship between blood pressure and venous return

Answer 11

when blood pressure during ventricular contraction is higher, venous return increases. There is a pressure gradient between venous and right atrial pressure. When gradient increases this aids venous return