Table of Contents
What is Heart and Definition
Heart is the organ that pumps BLOOD and maintains circulation. About the size of a closed fist, the heart resides in the chest between the LUNGS, slightly offset to the left behind the protective STERNUM (breastbone). It begins beating at about 3 weeks gestational age and during a typical life time contracts about 2.5 billion times. The heart’s four chambers contract in coordinated sequence to pump blood to the lungs and to the body, circulating the body’s 5- to 6-liter blood supply through the network of arteries and veins of the cardiovascular system up to three times a minute. Synchronized electrical impulses orchestrate the contractions. One-way valves direct the flow of blood into, through, and out of the heart. The right heart handles deoxygenated blood; the left heart handles oxygenated blood.
Health conditions that can affect the heart
The heart’s blood supply comes from the CORONARY ARTERIES, which arise from the root of the AORTA and encircle the heart. The heart has a substantial oxygen appetite; the coronary arteries deliver 20 percent of the body’s blood supply and 70 percent of the blood’s oxygen content to the heart. The heart is a remarkably sturdy and reliable structure that can withstand significant damage and still function adequately to supply the body’s needs for oxygen and other nutrients.
For further discussion of the heart within the context of cardiovascular structure and function, please see the overview section “The Cardiovascular System.”