This system consists of the heart and the blood vessels. Vessels that carry blood away from the heart are called arteries and those that carry blood toward the heart are called veins. Capillaries, short, thin-walled vessels, lie within the various organs and connect arteries to veins.
The cardiovascular system consists of the heart (box at left) and blood vessels. Vessels leaving the heart are called arteries (curved tube at upper left corner) which give rise to smaller vessels called arterioles (curved tube at upper right corner). These give rise to capillaries (lower right corner) that recombine to form veins (lower left corner) which return blood to the heart.
The central nervous system (box in center) has two cardiac centers (CA and CI circles) and two centers that control blood vessels (VI and VD circles). Nerves (solid and dashed lines) enter and leave the central nervous system.
Interstitial fluid that surrounds tissues is represented as the area inside the circle of vessels beside the capillary.
The block arrow (top of heart box) represents blood flowing from the heart into the arterial system; CO is cardiac output, the volume of blood leaving the heart each minute. The block arrow (bottom of heart box) represents blood flowing from the venous system into the heart; VR is venous return, the volume of blood returning to the heart each minute. The block arrows along the vessels represent the flow of blood along its pressure gradient. The donut structure at the beginning of the capillary represents the precapillary sphincter muscles that open and close to regulate the flow of blood into capillary beds.
Last update: 7/19/2005