Question

multiple select question
select all that apply
which of these are mechanisms of venous return?

□ gravity

□ respiration (the thoracic pump)

□ cardiac suction

□ increased blood pressure in the veins (as compared to the arteries)

□ muscle contraction (the skeletal muscle pump)

Explanation:

To determine the mechanisms of venous return:

• Gravity: Helps blood flow from the head and neck back to the heart.
• Respiration (thoracic pump): Changes in thoracic pressure during breathing assist in drawing blood into the thorax.
• Cardiac suction: The atria's relaxation creates a suction that pulls blood into the heart from veins.
• Increased blood pressure in veins (vs arteries): Veins have lower pressure than arteries, so this is incorrect.
• Muscle contraction (skeletal muscle pump): Contraction of skeletal muscles squeezes veins, pushing blood toward the heart.

Answer:

A. Gravity, B. Respiration (the thoracic pump), C. Cardiac suction, E. Muscle contraction (the skeletal muscle pump)