Question

Why does the body need skeletal muscle contraction, pressure changes during breathing, and vasoconstriction to move blood through the veins?

A. The blood pressure in the veins is too low to push blood toward the heart.
B. Veins contain valves which partially obstruct blood flow in them.
C. Veins are so superficial that the force of the heart can't reach them.

Answer 1

The body needs skeletal muscle contraction, pressure changes during breathing, and vasoconstriction to move blood through the veins.

Step-by-step explanation:

The body needs skeletal muscle contraction, pressure changes during breathing, and vasoconstriction to move blood through the veins for several reasons.

1. The blood pressure in the veins is too low to push blood toward the heart, so skeletal muscle contraction helps increase the pressure within the veins, allowing the blood to flow back to the heart.
2. Veins contain valves which partially obstruct blood flow in them. When surrounding skeletal muscles contract, they exert pressure on nearby veins and open valves superior to the contracting muscles, allowing blood to flow through. The valves inferior to the contracting muscles close to prevent blood from seeping back downward.
3. Veins are more superficial than arteries, and the force of the heart alone may not be sufficient to reach them. Skeletal muscle contraction assists in venous blood flow, especially in veins located further away from the heart.