What happens to blood in the deep calf veins during contraction?

• A. Blood volume in deep calf veins is squeezed upward toward the heart
• B. Deep calf veins fill with arterial blood
• C. Deep calf valves close and trap blood
• D. Deep calf veins collapse

Answer: (A)

When the calf muscles contract, they squeeze the deep veins of the leg, pushing blood upward toward the heart. The veins have one-way valves that open in the direction of flow during contraction and prevent backflow when the muscle relaxes, ensuring the blood moves upward rather than pooling downward. This calf muscle pump is key for venous return against gravity. Arterial blood filling the veins isn’t part of this process, the valves don’t trap blood during contraction, and the veins don’t collapse—they’re compressed to propel blood upward.