Circulatory System

Blood is circulated through the body by the pumping action of the heart. With each rhythmic beat, blood is pushed under high pressure and velocity away from the heart, initially through the main artery, the aorta. As blood travels through the capillary beds, which reach nearly every cell in the body, its flow slows significantly, aiding in gas and nutrient exchange and allowing fluid diffusion into the interstitial space. After passing through the capillaries to the venules, veins and eventually the main venae cavae, the flow rate increases again but remains much slower than the initial rate in the aorta. In veins, blood moves primarily due to the rhythmic contraction of smooth muscle in the vessel walls and the assistance of skeletal muscle movements as the body moves. Blood flow through the capillary beds is regulated according to the body’s needs, directed by nerve and hormone signals. *LICENSES AND ATTRIBUTIONS CC licensed content, Shared previously, 3.8.5 Blood Flow and Blood Pressure Regulation, Authored by: OpenStax College. License: CC BY: Attribution. License Terms: Download for free at:http://cnx.org/contents/41UfyQJ1@1.10:YHr_K7OM@5/Blood-Flow-and-Blood-Pressure-* ## Keywords circulatory system circulatory system of the body lungs pulmonary circulation heart vein artery