c. Capillaries. The capillaries are located throughout all tissues of the body.
No individual cell is more than two cells away from a capillary. The networks of
capillaries in the tissues are often called capillary beds.
10-22. PATTERNS OF BLOOD CIRCULATION
Blood vessels make up a closed system, since there is no place in the system
where whole blood can leave.
a. Direction of Flow of Arteries and Veins. Arteries carry blood from the
chambers of the heart to the tissue of the body. Veins carry blood from the tissues to
the chambers of the heart. (Coronary arteries carry blood from the chambers of the
heart inside to the walls of the heart outside.)
b. Two-Cycle System. It is also a two-cycle system (Figure 10-2). It involves
both the pulmonary cycle and the systemic cycle. Blood circulates through two circuits.
In the pulmonary cycle, blood circulates from the heart to the lungs and back to the
heart. In the systemic cycle, blood circulates from the heart to the rest of the body and
back to the heart.
Figure 10-2. Cardiovascular circulatory pattern.