Explain what is meant by the terms respiratory pump and skeletal muscle pump. Wh

Both refer to pressure exerted on the blood in veins that assist in venous return. During the pressure changes in the thoracic cavity associated with normal breathing, pressure in the thoracic portion of the inferior vena cava fluctuates, resulting in blood being pulled upward in the vena cava during each inhalation. Contractile activity of normal skeletal muscle momentarily squeezes the veins within and near the muscles, also helping to propel the blood. These and other slight pressure changes are essential because the overall pressure gradient of the venous system is low.