Final answer:
The contractions of the ventricles generate the pressure needed to force fluid from plasma through capillaries. It is during ventricular systole that this pressure is high enough to overcome pulmonary
Step-by-step explanation:
The pumping of the heart, specifically the contractions of the ventricles, generates the pressure responsible for forcing fluid from plasma as it passes through capillaries. During the cardiac cycle, the ventricles undergo ventricular systole, where they contract and increase pressure inside the chambers. This high ventricular pressure propels blood into the pulmonary trunk from the right ventricle and into the aorta from the left ventricle, overcoming the pressure in the pulmonary trunk and aorta. As this pressure gradient causes blood to move, it ultimately contributes to the flow through the capillary beds. Substances required by the cells diffuse out of the blood, while waste products diffuse in.
The cardiac cycle involves both the relaxation and contraction of the heart chambers, ensuring continuous blood flow. Pressure within the heart varies at different phases of this cycle, moving blood efficiently through the body's circulatory system. As a result, the heart effectively serves as the pump, maintaining circulation and enabling nutrient, gas, and waste exchange at the capillary level.and aortic pressures, allowing blood to circulate throughout the body and facilitating exchange at the capillary level.