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The Heart

About Dr Abdul Hafeez Chaudhry

Structure of the Heart
The heart is a muscular organ located just to the left of the breast bone (sternum). It is about the size of your fist, and this amazing muscle pumps 4300 gallons of blood a day. The heart has four chambers:

Atria. The top two chambers that receive blood from the body or lungs.
Ventricles. The bottom two chambers. The right ventricle pumps blood to the lungs to pick up oxygen, The left ventricle pumps blood to the rest of the body and is the strongest chamber.
Valves. There are four valves in the heart that help to direct blood flow. As they open and close, the valves produce sounds that can be heard with a stethoscope. The heart sounds can often tell your doctor about your hearts function.

Function of the Heart
Every cell in your body needs oxygen in order to live and function. The role of the heart is to deliver the oxygen-rich blood to every cell in the body.The arteries are the passageways through which the blood is delivered. The largest artery is the aorta, which branches off the heart and then divides into many smaller arteries. The veins carry the deoxygenated blood back to the lungs to pick up more oxygen, and then back to the heart once again. Blood flows continuously through the circulatory system, and the heart muscle is the pump which makes it all possible!

                                                            

Coronary Arteries
Your heart, just like all other muscles in the body, needs its own supply of oxygen in order to function properly. Although its chambers contain blood, the heart receives no nourishment from the blood inside the chambers. The heart gets its blood supply from the coronary arteries. The two major coronary arteries (the right coronary artery and the left main coronary artery) branch off the aorta, and then divide into many smaller arteries that lie in the heart muscle and feed the heart.

The Matter Of The Heart
The heart you see drawn on the average Valentine is only a rough representation of the actual structure of the heart. Your heart is actually shaped more like an upside-down pear. The human heart is primarily a shell. There are four cavities, or open spaces, inside the heart that fill with blood. Two of these cavities are called atria. The other two are called ventricles. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest. The left ventricle contracts most forcefully, so you can best feel your heart pumping on the left side of your chest.

The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle.

The top of the heart connects to a few large blood vessels. The largest of these is the aorta, or main artery, which carries nutrient-rich blood away from the heart. Another important vessel is the pulmonary artery which connects the heart with the lungs as part of the pulmonary circulation system. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava. They are called "vena cava" because they are the "heart's veins." The superior is located near the top of the heart. The inferior is located beneath the superior.

The heart's structure makes it an efficient, never-ceasing pump. From the moment of development through the moment of death, the heart pumps. The heart, therefore, has to be strong. The average heart's muscle, called cardiac muscle, contracts and relaxes about 70 to 80 times per minute without you ever having to think about it. As the cardiac muscle contracts it pushes blood through the chambers and into the vessels. Nerves connected to the heart regulate the speed with which the muscle contracts. When you run, your heart pumps more quickly. When you sleep, your heart pumps more slowly.

Considering how much work it has to do, the heart is surprisingly small. The average adult heart is about the size of a clenched fist and weighs about 11 ounces (310 grams). Located in the middle of the chest behind the breastbone, between the lungs, the heart rests in a moistened chamber called the pericardial cavity which is surrounded by the ribcage. The diaphragm, a tough layer of muscle, lies below. As a result, the heart is well protected.

To monitor the heart, scientists can use x-ray or scanning technology to get a picture. To really explore the heart, scientists have to perform surgery. Heart surgery is very risky because the heart's pumping action is so critical for survival. If the heart stops pumping, the body cannot survive. Before beginning heart surgery, doctors connect the patient to a machine that pumps the blood for the heart. Only then is it safe for the doctor to stop the heart in order to operate.

Courtesy,
Franklin Institute online