Circulatory System

The circulatory system is the system of organs and tissues involved in the circulation of blood and lymph throughout the body. The arterioles, capillaries, veins, heart, and lymph all form part of the circulatory system. The main function of this system is to transport essential materials (oxygen, glucose, electrolytes) to and from cells.

Arteries are defined as any blood vessels carrying blood away from the heart. The arterial walls are thicker and more muscular than those of the veins, since the pressure of blood is greater in the arteries than in the veins. The largest artery is the aorta, which transports blood from the heart to the rest of the body. The arteries narrow into arterioles, which subsequently narrow to create capillaries.

Veins are defined as any blood vessels which carry blood to the heart. Double valves break veins into chambers, thus preventing the back flow of blood.

Capillaries are microscopic blood vessels, a single cell layer in thickness. Capillaries join the arteries to the veins and are the sites where essential nutrients are exchanged between the blood and component cells of the body.


References
Antony, C.P. & G.A. Thibodeaw. 1979. Textbook of Anatomy and Physiology. The C.V. Mosby Company, St. Louis. 731 pp.

Lockhart, R.D., G.F. Hamilton, et. al. 1974. Anatomy of The Human Body. Faber and Faber Limited. London. 697 pp.

Van Amerongen, C. The Way Things Work; Book Of The Body. New York: Simon and Schuster, 1979.