Question

how does the respiratory pump aid venous return?
a exhaling and blowing out draws blood toward the tissues.
b low pressure during inhalation draws blood toward the heart.
c skeletal muscle contractions in the extremities pushes blood through veins.
d valves in veins promote venous return.

Explanation:

• Option A: Exhaling and blowing out does not draw blood toward the tissues in the context of the respiratory pump aiding venous return.
• Option B: During inhalation, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity. This creates a lower - pressure environment in the thoracic cavity compared to the abdominal cavity. As a result, blood is drawn from the abdominal veins (where pressure is relatively higher) towards the heart (in the thoracic cavity). This is how the respiratory pump (related to the act of breathing) aids venous return.
• Option C: Skeletal muscle contractions in the extremities are part of the skeletal - muscle pump, not the respiratory pump.
• Option D: Valves in veins prevent back - flow of blood, but this is a structural feature of veins and not directly related to the respiratory pump.

Answer:

B. Low pressure during inhalation draws blood toward the heart.