CONTENT

INTRODUCTION:

The Heart is made up of a powerful muscle called Myocardium. The Myocardium is composed of cardiac muscle fibers that contracts and causes a wringing type of action. The size of you heart is a little larger than the size of your fist. The location of the heart is about left-center of your chest. The heart are two separate pumps that continuously sends blood throughout the body carrying nutrients, oxygen, and helping remove harmful wastes.

The right side of the heart receives blood low in oxygen. The left side of the heart receives blood that has been oxygenated by the lungs. The blood is then pumped out into the Aorta and to all parts of the body. The Heart Diagram above and the information that follows will give a better understanding of the heart structure and how the blood circulates through the heart.

MEANING:

The heart is a muscular organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek , kardia, for "heart."

The heart of a vertebrate is composed of cardiac muscle, an involuntary striated muscle tissue which is found only within this organ. The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during a lifetime (about 66 years). It weighs on average 250 g to 300 g in females and 300 g to 350 g in males.

STRUCTURE:

The structure of the heart varies among the different branches of the animal kingdom. (See Circulatory system.) Cephalopods have two "gill hearts" and one "systemic heart". Fish have a two-chambered heart that pumps the blood to the gills and from there it goes on to the rest of the body. In amphibians and most reptiles, a double circulatory system is used, but the heart is not always completely separated into two pumps. Amphibians have a three-chambered heart.

Birds and mammals show complete separation of the heart into two pumps, for a total of four heart chambers; it is thought that the four-chambered heart of birds evolved independently from that of mammals.

In the human body, the heart is usually situated in the middle of the thorax with the largest part of the heart slightly offset to the left (although sometimes it is on the right, see dextrocardia), underneath the sternum. The heart is usually felt to be on the left side because the left heart (left ventricle) is stronger (it pumps to all body parts). The left lung is smaller than the right lung because the heart occupies more of the left hemithorax. The heart is fed by the coronary circulation and enclosed by a sac known as the pericardium and is surrounded by the lungs.

The pericardium comprises two parts: the fibrous pericardium, made of dense fibrous connective tissue; and a double membrane structure (parietal and visceral pericardium) containing a serous fluid to reduce friction during heart contractions. The heart is located in the mediastinum, the central sub-division of the thoracic cavity. The mediastinum also contains other structures, such as the esophagus and trachea, and is flanked on either side by the right and left pulmonary cavities, which house the lungs.

The apex is the blunt point situated in an inferior (pointing down and left) direction. A stethoscope can be placed directly over the apex so that the beats can be counted. It is located posterior to the 5th intercostal space just medial of the left mid-clavicular line. In normal adults, the mass of the heart is 250-350 g (9-12 oz), or about twice the size of a clenched fist (it is about the size of a clenched fist in children), but extremely diseased hearts can be up to 1000 g (2 lb) in mass due to hypertrophy. It consists of four chambers, the two upper atria and the two lower ventricles.

Right Atrium:

The Right Atrium is larger than the Left Atrium but has thinner walls. The Right Atrium has two major veins that returns blood to the heart from all parts of the body. Two major veins returning the blood to the heart are the Superior Vena Cava and the Inferior Vena Cava. These two veins are sometimes called the "Great Veins". The Superior Vena Cava returns the deoxygenated blood from the upper part of the body and the Inferior Vena Cava returns the deoxygenated blood from the lower part of the body. The Right Atrium also receives blood back from the heart muscle itself. After the blood is collected in the Right Atrium it is pumped into the Right Ventricle through the Tricuspid Valve (three leaf valve).

Left Atrium:

The Left Atrium receives blood from four Pulmonary Veins. The blood received from the lungs has been oxygenated. The oxygenated blood that is collected in Left Atrium is then pumped into the Left Ventricle through the Bicuspid Valve.

Right Ventricle:

The Right Ventricle receives blood from the Right Atrium. When the Heart contract the blood is forced out through the Pulmonary Semilunar Valve into the Pulmonary Artery. The Pulmonary Semilunar Valve is a three flap valve that stops the backflow of blood. The walls of the Right Ventricle are a little thicker than the Right Atrium.

Left Ventricle:

The chamber of the Left Ventricle has walls that are three times the thickness of the Right Ventricle. This is important because the oxygenated blood that it receives from the Left Atrium has to be pump throughout the body. The Bicuspid Valve closes and the blood is collected in the Left Ventricle. The closing of the Bicuspid Valve stops the backflow of blood. When the Heart muscle contracts the blood is forced through the Aortic Semilunar Valve which has the same features as the Pulmonary Valve. The blood then passes through the Aortic Semilunar Valve into the Aorta.

Aorta:

The Aorta is the largest blood vessel in the body. The inner diameter of the Aorta is about 1 inch. The Aorta carries oxygenated blood to every other part of the body. The Aorta receives it's blood from the Left Ventricle.

Septum:

The Septum is a partition that separates the right and left sides of the Heart. There are two separate regions of the Septum. They are the Interatrial Septum that separates the Atriums and the Interventrial Septurm that separates the Ventricles. The Interatrial Septum is only present in the fetal period and is open during this period. The Interatrial Septum closes at the time of birth. The Interventrial Septum is suppose to be closed all the time but sometimes an opening is present at birth. This would be considered a Congenital heart disease.

Superior Vena Cava:

The importance of the Superior Vena Cava is to return blood back to the Right Atrium from the upper part of the body. It is one of the largest veins in the body.

Inferior Vena Cava:

The Inferior Vena Cava is important for carrying the blood back to the Right Atrium from the lower part of the body.

Pulmonary Arteries:

The Pulmonary Arteries carry the blood from the Right Ventricle to both of the lungs. There the blood is oxygenated and sent to the Left Atrium in the heart.

Pulmonary Veins:

The Pulmonary Veins carry the oxygenated blood back to the Left Atrium in the heart.

What Is a Heart Attack?

A heart attack occurs when blood flow to a section of heart muscle becomes blocked. If the flow of blood isn’t restored quickly, the section of heart muscle becomes damaged from lack of oxygen and begins to die.

Heart attack is a leading killer of both men and women in the United States. But fortunately, today there are excellent treatments for heart attack that can save lives and prevent disabilities. Treatment is most effective when started within 1 hour of the beginning of symptoms.

Other Names for a Heart Attack :

#Myocardial infarction or MI

#Acute myocardial infarction or AMI

#Acute coronary syndrome

#Coronary thrombosis

#Coronary occlusion

CAUSES:

Most heart attacks occur as a result of coronary artery disease (CAD). CAD is the buildup over time of a material called plaque on the inner walls of the coronary arteries. Eventually, a section of plaque can break open, causing a blood clot to form at the site. A heart attack occurs if the clot becomes large enough to cut off most or all of the blood flow through the artery.

The blocked blood flow prevents oxygen-rich blood from reaching the part of the heart muscle fed by the artery. The lack of oxygen damages the heart muscle. If the blockage isn’t treated quickly, the damaged heart muscle begins to die.

Heart attack also can occur due to problems with the very small, microscopic blood vessels of the heart. This condition is called microvascular disease. It’s believed to be more common in women than in men.

Another less common cause of heart attack is a severe spasm (tightening) of a coronary artery that cuts off blood flow through the artery. These spasms can occur in coronary arteries that don’t have CAD. It’s not always clear what causes a coronary artery spasm, but sometimes it can be related to:

#Taking certain drugs, such as cocaine

#Emotional stress or pain

#Exposure to extreme cold

#Cigarette smoking

The animation below shows how a heart attack occurs. Click the “start” button to play the animation. Written and spoken explanations are provided with each frame. Use the buttons in the lower right corner to pause, restart, or replay the animation, or use the scroll bar below the buttons to move through the frames.

SIGNS & SYMPTOMS:

Not all heart attacks begin with a sudden, crushing pain that is often shown on TV or in the movies. The warning signs and symptoms of a heart attack aren’t the same for everyone. Many heart attacks start slowly as mild pain or discomfort. Some people don’t have symptoms at all (this is called a silent heart attack).

Chest Pain or Discomfort :

The most common symptom of heart attack is chest pain or discomfort. Most heart attacks involve discomfort in the center of the chest that lasts for more than a few minutes or goes away and comes back. The discomfort can feel like uncomfortable pressure, squeezing, fullness, or pain. It can be mild or severe. Heart attack pain can sometimes feel like indigestion or heartburn.

The symptoms of angina can be similar to the symptoms of a heart attack. Angina is pain in the chest that occurs in people with coronary artery disease, usually when they’re active. Angina pain usually lasts for only a few minutes and goes away with rest. Angina that doesn’t go away or that changes from its usual pattern (occurs more frequently or occurs at rest) can be a sign of the beginning of a heart attack and should be checked by a doctor right away.

Other Common Signs and Symptoms:

Other common signs and symptoms that a person can have during a heart attack include:
#Upper body discomfort in one or both arms, the back, neck, jaw, or stomach

#Shortness of breath may often occur with or before chest discomfort

#Nausea (feeling sick to your stomach), vomiting, lightheadedness or fainting, or breaking out in a cold sweat

#Not everyone having a heart attack experiences the typical symptoms. If you’ve already had a heart attack, your symptoms may not be the same for another one. The more signs and symptoms you have, the more likely it is that you’re having a heart attack.

PREVENTION:

Healthy Lifestyle Choices :

Healthy lifestyle choices to help prevent heart attack include:

Following a low-fat diet rich in fruits and vegetables. Pay careful attention to the amounts and types of fat in your diet. Lower your salt intake. These changes can help lower high blood pressure and high blood cholesterol.

#Losing weight if you're overweight or obese.

#Quitting smoking.

#Doing physical activity to improve heart fitness. Ask your doctor how much and what kinds of physical activity are safe for you.

Treat Related Conditions :

In addition to making lifestyle changes, you can help prevent heart attacks by treating conditions you have that make a heart attack more likely:

#High blood cholesterol. You may need medicine to lower your cholesterol if diet and exercise aren't enough.

#High blood pressure. You may need medicine to keep your blood pressure under control.

#Diabetes (high blood sugar). If you have diabetes, control your blood sugar levels through diet and physical activity (as your doctor recommends). If needed, take medicine as prescribed.