Question

multiple choice question
the thoracic pump does which of the following?

massages blood from the limbs towards the heart
acts as the major force in venous flow
draws blood into the atria from the vena cavae and pulmonary veins
aids in venous flow from the abdominal to the thoracic cavity

Explanation:

To solve this, we analyze each option:

• "Massages blood from the limbs towards the heart" describes the muscle pump (from limb muscles), not the thoracic pump.
• "Acts as the major force in venous flow" is incorrect; the primary force for venous flow is the pressure gradient from the heart, with the thoracic pump being an aid.
• "Draws blood into the atria from the vena cavae and pulmonary veins" is related to atrial filling, but the thoracic pump's role is in venous return from abdominal to thoracic (due to pressure changes during respiration).
• "Aids in venous flow from the abdominal to the thoracic cavity" is correct. During inhalation, the thoracic cavity expands, decreasing pressure there, and increasing abdominal pressure (from diaphragm descent), which pushes abdominal venous blood (like from the inferior vena cava) into the thoracic cavity, aiding venous return.

Answer:

D. Aids in venous flow from the abdominal to the thoracic cavity