During relaxation, which statement about proximal deep valves is true?

During relaxation, which statement about proximal deep valves is true?

• A. Prox deep valves close
• B. Distal deep valves open
• C. Blood flows into deep calf and muscular veins
• D. Hydrostatic pressure column is interrupted

Answer: (A)

During relaxation, the calf muscle pump isn’t actively squeezing the veins, and gravity tends to push blood downward toward the feet. The proximal deep valves close to prevent backflow from the proximal segment into the distal veins. This closure interrupts the hydrostatic pressure column that would otherwise extend down the leg, helping to keep venous return oriented toward the heart and ready for the next contraction. If the proximal valve didn’t close, reflux into the distal veins could occur during relaxation, undermining forward flow. The other statements don’t fit this mechanism: opening distal valves wouldn’t prevent backward flow in this relaxed state, and while the hydrostatic column is interrupted, the proximate cause is the valve closure itself.

During relaxation, the calf muscle pump isn’t actively squeezing the veins, and gravity tends to push blood downward toward the feet. The proximal deep valves close to prevent backflow from the proximal segment into the distal veins. This closure interrupts the hydrostatic pressure column that would otherwise extend down the leg, helping to keep venous return oriented toward the heart and ready for the next contraction. If the proximal valve didn’t close, reflux into the distal veins could occur during relaxation, undermining forward flow. The other statements don’t fit this mechanism: opening distal valves wouldn’t prevent backward flow in this relaxed state, and while the hydrostatic column is interrupted, the proximate cause is the valve closure itself.