Which pump is driven by changes in thoracic and abdominal pressure during breathing?

• A. Skeletal Muscle Pump
• B. Pocket Valves
• C. Venous Pressure (Pv)
• D. Respiratory Pump

Answer: (D)

The respiratory pump uses the pressure changes that occur with breathing to help move blood back to the heart. When you inhale, the diaphragm lowers and the chest cavity expands, causing intrathoracic pressure to fall. This negative pressure pulls venous blood toward the heart through the large veins in the chest. At the same time, the pressure in the abdomen rises as the abdominal contents are pushed downward, helping push blood from the abdominal veins toward the heart. The net result is an increased return of venous blood to the right atrium during inspiration. This differs from the skeletal muscle pump, which relies on muscle contractions to push blood along the veins, and from pocket valves, which are valves that prevent backflow but do not actively move blood. Venous pressure is a measurement, not a pump.