Illustrated Systole & Diastole of the Heart & Coronary Anatomy Human

The human heart has four chambers and two halves. There are two areas of entry for blood: the right atrium and the left atrium. There are two major pumping areas: the right ventricle and the left ventricle. The right ventricle provides the momentum for pulmonary circulation. The right ventricle pumps deoxygenated blood out of the heart by pushing it through the pulmonary trunk and pulmonary arteries and sending it to the lungs. The left ventricle provides the momentum for systemic circulation. It sends newly oxygenated blood through the aorta on its way to the body.

Interestingly, “atrium” is itself a Latin word meaning “central court or main room of an ancient Roman house, room which contains the hearth.” In fact Aristotle, and later Galen, believed that the heart is the source of the body’s heat. Aristotle proposed that passions originate in the heart. The word “ventricle” comes from Latin as well, ventriculus, meaning, “stomach.”

The pumping action of the heart, the cardiac cycle, occurs in five phases. The two most responsible for the movement of blood are known as systole and diastole. One systolic event plus one diastolic event creates a single heartbeat. The frequency of these events is known as the heart rate. The cardiac cycle is coordinated by electrical impulses originating in the sinoatrial node and the atrioventricular node. Unlike other cells in the body, the cells of the heart are able to contract and expand on their own without external nerve impulses.

As the phase of diastole begins, the whole heart are relaxed and the ventricles are filling with blood. The atrioventricular valves are open. These AV valves include the (1) mitral valve, which is between the left atrium and the left ventricle, and (2) the tricuspid valve, which is between the right atrium and the right ventricle. The semilunar valves are open. Semilunar valves include (1) the aortic valve, which is between the left ventricle and the aorta, and (2) the pulmonic valve, which is between the right ventricle and the pulmonary artery.

During the systole the atria contract and compress to push the blood with an additional filling of the ventricles. The atrioventricular valves are closed. The semilunar valves are closed.

According to Regina Avraham, in her book, “The Circulatory System” (2000. Philadelphia, PA: Chelsea House Publishers), a kitchen faucet would have to be turned on all the way for over 45 years to equal the amount of blood pumped by the heart in an average lifetime.

The coronary vessels are responsible for the delivery of blood to the heart muscle, or myocardium. Coronary circulation enables oxygen delivery. Cardiac veins, on the other hand, return deoxygenated blood to the lungs. Those coronary vessels which run along the surface of the heart are known as epicardial arteries; those which run deep are called the subendocardial arteries.

Some regions of the body have redundant circulation, but not the regions to which these arteries deliver blood. There is no other way for blood to reach the heart other than these arteries. This is why blood circulation through the coronary arteries is so critical. Because these vessels are narrow, they are susceptible to atherosclerosis, which can lead to a blockage. If the vessels are blocked and there is no passage of blood through the coronary artery, that region of the heart will begin to die, causing angina or a heart attack.

In the United States, 2 people suffer from a coronary every second, and one person dies from a coronary event every second. It is the single leading cause of death in the U.S. The greatest risk factors, in this order, include, inactivity, obesity, high blood pressure, cigarette smoking, high cholesterol, and diabetes. These facts come from the Centers for Disease Control.