Unit D

Module 7 ~ Lesson 1

 Pathways of Circulation

It is important to distinguish between pulmonary circulation and systemic circulation. Pulmonary circulation occurs when the right side of the heart pumps deoxygenated blood to the lungs via the pulmonary arteries. Pulmonary veins bring oxygenated blood back to the left side of the heart to be distributed to the rest of the body through the arteries. In the pulmonary system, arteries carry deoxygenated blood and veins carry oxygenated blood.     

This is different from systemic circulation. Systemic circulation involves the circulation of blood to all other parts of the body aside from the lungs. This is the portion of the cardiovascular system that carries oxygenated blood away from the heart, to the body, and then returns deoxygenated blood back to the heart.


Read "Pathways of the Circulatory System" on pages 276 and 277 of your textbook.


Arteries carry blood away from the heart.
Veins carry blood to the heart.
Veins are not elastic and require valves to move blood back to the heart. Otherwise, blood would pool in the extremities. Arteries are elastic so they can expand with the force of blood as it pumps from the heart. Arteries expand as ventricles relax and keep the blood flowing. Capillaries are very small and spread out in a network that allows single blood cells to be exposed to individual cells.