Circulatory System

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The Pathways of Circulation

The blood moves through our body in a continuous pathway, in which there are two major parts. The pulmonary circulation that carries blood between the heart and the lungs. It begins at the right ventricle and ends at the left atrium. The second is the systemic circulation, which starts at the left ventricle and ends at the right atrium, carrying blood to the rest of the body.

Pulmonary Circulation

In this circulation oxgen-poor blood is pumped out of the right ventricle of the heart into the lungs through the pulmonary arteries. These are the only arteries in the body that carry deoxygenated blood. Then blood returns to the heart through the pulmonary veins, which are the only veins in the body that carry oxygen-rich blood. The lungs are the only organs directly connected to both chambers of the heart.

Systemic Circulation

In this circulation oxygen-rich blood leaving the heart passes through the aorta and into the arteries that supply blood to every part of the body. Sytemic circulation supplies every major organ with, blood including the heart. The heart muscle doesn’t get oxygen and nutrients from the enormous amount of blood that passes through it. Instead, a pair of coronary arteries leading from the aorta carry blood through the tissues of the heart. These arteries branch into arterioles and then into capillaries, forming a lacy network throughout the heart. The capillaries leed into veins through which blood returns to the right atrium.
In general, blood travels through only one set of capillaries before it returns to the heart. But there is a special circulation known as the hepatic portal system that is an exception to this rule. Capillaries that line the walls of the digestive system absorb food, minerals, and water. Blood in these capillaries is collected into veins, but these veins do not lead directly to the heart. Instead, they are carried to the liver by the he...