The Human Heart Video Transcription

INTRODUCTION

Hi, I'm Dr. Charles Machel and, along with St. Jude Medical, we have created the following video series to provide you with more information on the heart. I will discuss how the heart works, the coronary circulation and the heart's anatomy.

About the size of your fist, the human heart is the most important muscle in the body. It beats more than 100,000 times a day, pumping about 2,000 gallons of blood through a 60,000-mile network of vessels in the body.

HEART ANATOMY

The human heart is made up of four major chambers. The right atrium, right ventricle, left atrium and left ventricle.

The right side of the heart receives blood that is low in oxygen from veins all over the body. It then pumps the blood, through the pulmonary artery, into the lungs where it will become re-oxygenated.

The left side of the heart receives this oxygen-rich blood from the lungs. Then, it pumps the blood through the aorta back out to the rest of the body through a complex network of arteries, arterioles, and capillaries.

While blood is circulating through the body, it delivers oxygen and nutrients to tissue through the arteries and picks up carbon dioxide through the veins. The veins return the de-oxygenated blood to the right atrium, and the cycle begins again.

The heart has four valves. Each valve is like a one-way door that keeps the blood in the heart flowing in the same direction. The valves are made up of two or three small but strong flaps of tissue called leaflets. Leaflets open to allow blood to flow through the valve, and close to prevent blood from flowing backward. The opening and closing of the valves is controlled by blood pressure changes within each heart chamber.

The tricuspid valve is positioned in the heart's right side, between the right atrium and right ventricle. The pulmonic valve separates the right ventricle from the pulmonary artery. The mitral valve is positioned in the heart's left side, between the left atrium and the left ventricle. And the aortic valve separates the left ventricle from the aorta.

HEART CIRCULATION

If the heart pumps oxygen-rich blood out to feed the body, what feeds the heart muscle itself?

As blood circulates through the heart, some of the blood flows into a set of much smaller blood vessels that provide blood directly to the heart. These arteries, called coronary arteries, surround or "crown" the heart. This separate circulatory system, called coronary circulation, keeps the heart nourished and oxygenated

The two main branches of the aorta that nourish the heart are the right and left main coronary arteries. Coronary artery disease - which occurs when there is a build up of cholesterol plaque - affects the arteries of this circulatory system and causes a decrease in blood flow to the heart muscle, resulting in possible damage to the heart or a heart attack.

HEART ARRHYTHMIAS

Every heart has its own rhythm - or beats - that are regulated by electrical impulses from your heart muscle. These impulses begin in the sinoatrial node and cause your heart to contract. Sometimes, the SA node is also referred to as your heart's natural pacemaker since it keeps the heart-rate constant and consistent. The impulses then travel to the atrioventricular node where the signal is checked and then sent through the ventricles which then causes them to contract, too. Your heart rate can change based upon external conditions such as diet, exercise, stress or even hormonal factors.

Thank you for viewing St. Jude Medical's video series on the human heart. This video was created to provide information about the heart. This is not a substitute for medical advice. If you have questions about the heart please talk to your physician.