Understanding the Heart

In order to better understand heart disease, it helps to first understand the normal function of the heart. The heart is a muscle, located in the left central area of the chest behind the sternum (breastbone) and ribs. It is about the size of an adult’s closed fist, and weighs less than one pound. There are four chambers in the heart, two on the right and two on the left. The two upper chambers are called the atria and the two lower chambers are called ventricles.

Heart Valves and Their Function

A heart valve is a ring-like structure with smooth leaflets (cusps). These cusps serve to control the flow and direction of blood as it passes through the heart chambers and out into the body. The heart has four main valves:

  • Tricuspid – located between the right atrium and the right ventricle
  • Mitral – between the left atrium and left ventricle
  • Pulmonic – between the right ventricle and lungs
  • Aortic – between the left ventricle and the body

Normal Function of the Heart

Each heartbeat begins when a special group of cells in the right atrium of the heart (the Sinus Node) sends an electrical signal that spreads throughout the atria to the Atrio-Ventricular (AV) Node. The AV Node connects to a special group of conducting fibers in the ventricles. As the electrical impulse travels through the heart, the heart contracts. This normally occurs 60-100 times each minute. Each contraction represents one heartbeat.

Coronary Arteries

The heart, along with the rest of the body, must have oxygen to do its job. The special blood vessels that supply the heart with oxygen-rich blood are called coronary arteries. They are located on the surface of the heart. There are two primary coronary arteries, the left and the right. Each of these arteries has smaller branches that help supply oxygen to the heart as well.

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