Disease can strike any part of the heart. However, the term heart disease usually means coronary artery disease (CAD), the most common form of heart disease. The condition affects the blood vessels that nourish the heart itself. CAD narrows the coronary arteries and so reduces the blood supply to the heart. About 5 per cent of the blood pumped from the heart goes directly to the coronary arteries. The blood carries the oxygen and dissolved nutrients (foods) the heart needs to do its work. The heart can store most nutrients. But it cannot store oxygen and needs a constant supply. Coronary artery disease may affect the heart's ability to pump by reducing or stopping the oxygen. Some people with CAD suffer severe pain. Others feel no pain and do not even know they have a heart problem. If the disease worsens, a heart attack may result. A heart attack damages the heart muscle or may even cause sudden death. Most cases of CAD can be treated, but the disease should be diagnosed (identified) as soon as possible.
Risk factors. Cardiologists cannot say for certain who will be stricken with coronary artery disease. However, medical research shows that certain conditions and habits may lead to the disease. Doctors call those conditions and habits risk factors. Some risk factors fall beyond a person's control. For example, CAD strikes more men than women and older people more than younger ones. In addition, the disease may run in a person's family. Several other risk factors involved in coronary artery disease can be controlled. The most important risk factor is the amount in the blood of a fatty substance called cholesterol. The higher a person's cholesterol level is, the more likely coronary artery disease will strike because the fatty deposits narrow the blood vessels. People can control the blood cholesterol level by reducing the amount of cholesterol and animal fats in the diet. See CHOLESTEROL.
Other controllable risk factors that may cause coronary artery disease include high blood pressure and cigarette smoking. High blood pressure forces the heart to work harder, which may bring on a heart attack. People can lower their blood pressure by losing weight, exercising, and eating less salt. Certain medicines also help reduce high blood pressure. Cigarette smokers are more likely to have CAD than nonsmokers. Heavy smokers run more than twice the risk of a heart attack than nonsmokers. But smokers who quit significantly reduce the risk of heart disease. Other risk factors that may contribute to the development of coronary artery disease include diabetes, extreme fatness, and stress.
Regular physical examinations often reveal the development of controllable risk factors. Doctors may then advise patients to quit smoking or to follow a specific diet to control high blood pressure, the cholesterol level, or weight.Causes.Nearly all coronary artery disease results from arteriosclerosis--a hardening, thickening, and loss of elasticity of the artery walls. In most cases, the inner layer of the artery wall becomes damaged, causing a form of arteriosclerosis called atherosclerosis. The inner walls of healthy arteries are smooth, and so blood flows easily. But in atherosclerosis, deposits of fats and calcium build up on the inner walls, hampering the blood flow through the artery. The fat and calcium deposits are called plaques. Plaques can completely block an artery and stop the blood flow. In addition, they can narrow an artery and so reduce blood flow enough to form a thrombus (blood clot). Plaques often crack, releasing substances that also can lead to blood clots. If a blood clot blocks a coronary artery, it causes a heart attack. A blood clot that occurs in an artery in the brain causes.
Saturday, February 28, 2009
WORKING OF HEART
Pumping blood to the lungs. Blood from the body that enters the right side of the heart contains carbon dioxide, a gaseous waste the cells produce in creating energy. Blood enters the right atrium through the superior vena cava and inferior vena cava. The atrium fills with blood and then contracts, squeezing the blood through the tricuspid valve into the right ventricle. After the ventricle is filled, pressure forces the tricuspid valve to close and the pulmonic valve, leading to the pulmonary artery, to open. The ventricle contracts, and the blood gushes through the pulmonary artery and into the lungs. In the lungs, carbon dioxide is removed from the blood and oxygen is added. The oxygenated blood then flows through the pulmonary veins to the left side of the heart.
Pumping blood throughout the body. Oxygenated blood from the lungs enters and fills the left atrium. The atrium then contracts, which squeezes the blood through the mitral valve into the left ventricle. After blood fills the ventricle, the mitral valve closes and the aortic valve opens. Blood pours into the aorta and flows through arteries to the body tissues. Other blood vessels transport blood between the heart and lungs. Pulmonary veins return blood from the lungs to the left atrium. The pulmonary artery carries blood from the right ventricle to the lungs. The aorta is the largest artery. It receives oxygenated blood from the left ventricle and, through numerous branches, distributes it throughout the body. The pulmonary artery and the aorta are sometimes called the great vessels.
The first arteries that branch from the aorta are the two major coronary arteries.
Valves regulate the flow of blood through the heart. The valves have flaps that open as blood pours from a chamber. When the flaps close, they prevent blood from flowing back into the chamber. Two valves separate the atria and the ventricles. They are called the atrioventricular valves or AV valves. The AV valve between the right atrium and right ventricle has three flaps and is called the tricuspid valve. The AV valve on the left side of the heart has two flaps and is called the mitral valve. The heart also has a valve, called a semilunar valve, between each ventricle and its great vessel--the pulmonary artery or the aorta. Each semilunar valve has three flaps shaped like half moons. When the right ventricle contracts, it delivers blood to the pulmonary artery.
Valves regulate the flow of blood through the heart. The valves have flaps that open as blood pours from a chamber. When the flaps close, they prevent blood from flowing back into the chamber. Two valves separate the atria and the ventricles. They are called the atrioventricular valves or AV valves. The AV valve between the right atrium and right ventricle has three flaps and is called the tricuspid valve. The AV valve on the left side of the heart has two flaps and is called the mitral valve. The heart also has a valve, called a semilunar valve, between each ventricle and its great vessel--the pulmonary artery or the aorta. Each semilunar valve has three flaps shaped like half moons. When the right ventricle contracts, it delivers blood to the pulmonary artery tricuspid and mitral valves open and blood begins to fill the ventricles. The autonomic nervous system controls the heart rate. Special cells send electrical impulses (nerve signals) through the heart, causing it to contract and relax rhythmically. The impulse begins in a small bundle of muscle fibers called the sinoatrial node, or S-A node. The S-A node is often called the pacemaker of the heart because it sets the pace of the heartbeat as it sends out rhythmic signals.
Pumping blood throughout the body. Oxygenated blood from the lungs enters and fills the left atrium. The atrium then contracts, which squeezes the blood through the mitral valve into the left ventricle. After blood fills the ventricle, the mitral valve closes and the aortic valve opens. Blood pours into the aorta and flows through arteries to the body tissues. Other blood vessels transport blood between the heart and lungs. Pulmonary veins return blood from the lungs to the left atrium. The pulmonary artery carries blood from the right ventricle to the lungs. The aorta is the largest artery. It receives oxygenated blood from the left ventricle and, through numerous branches, distributes it throughout the body. The pulmonary artery and the aorta are sometimes called the great vessels.
The first arteries that branch from the aorta are the two major coronary arteries.
Valves regulate the flow of blood through the heart. The valves have flaps that open as blood pours from a chamber. When the flaps close, they prevent blood from flowing back into the chamber. Two valves separate the atria and the ventricles. They are called the atrioventricular valves or AV valves. The AV valve between the right atrium and right ventricle has three flaps and is called the tricuspid valve. The AV valve on the left side of the heart has two flaps and is called the mitral valve. The heart also has a valve, called a semilunar valve, between each ventricle and its great vessel--the pulmonary artery or the aorta. Each semilunar valve has three flaps shaped like half moons. When the right ventricle contracts, it delivers blood to the pulmonary artery.
Valves regulate the flow of blood through the heart. The valves have flaps that open as blood pours from a chamber. When the flaps close, they prevent blood from flowing back into the chamber. Two valves separate the atria and the ventricles. They are called the atrioventricular valves or AV valves. The AV valve between the right atrium and right ventricle has three flaps and is called the tricuspid valve. The AV valve on the left side of the heart has two flaps and is called the mitral valve. The heart also has a valve, called a semilunar valve, between each ventricle and its great vessel--the pulmonary artery or the aorta. Each semilunar valve has three flaps shaped like half moons. When the right ventricle contracts, it delivers blood to the pulmonary artery tricuspid and mitral valves open and blood begins to fill the ventricles. The autonomic nervous system controls the heart rate. Special cells send electrical impulses (nerve signals) through the heart, causing it to contract and relax rhythmically. The impulse begins in a small bundle of muscle fibers called the sinoatrial node, or S-A node. The S-A node is often called the pacemaker of the heart because it sets the pace of the heartbeat as it sends out rhythmic signals.
HEART STRUCTURE
Each person's heart is about the size of the person's fist. A newborn baby's heart weighs about 2/3 ounce (19 grams). An adult's heart weighs from 9 to 11 ounces (255 to 312 grams). The heart lies near the middle of the chest, between the lungs. The heart lies closer to the front of the chest than to the back and slightly to the left side. Muscular walls. The heart consists chiefly of muscle. Heart muscle, also called myocardium or cardiac muscle, forms the walls of the heart as well as the septum, a wall that divides the left and right sides of the heart. All the muscles contract and relax, thereby pushing blood through the heart. A membrane called the epicardium covers the outer surface of the heart. Another membrane, the pericardium, surrounds the epicardium.
It completely encloses the heart and extends above the blood vessels that emerge from the top of the heart. A slippery fluid between the epicardium and the pericardium enables the heart to contract smoothly. Heart muscle differs from the other muscles of the body--skeletal and smooth muscles. Skeletal muscles, such as those in the arms and legs, have long fibers with alternate dark and light bands called striations. We can consciously control the skeletal muscles. Smooth muscles form the walls of the stomach, intestines, and most other internal organs. The muscles lack striations, and we do not consciously control them.
They work automatically. Heart muscle has striations like skeletal muscle. But it contracts and relaxes automatically like smooth muscle. In addition, heart muscle cells act as one cell. When one heart muscle cell contracts or relaxes, the cells around it do the same. For that reason, the heart beats continuously and rhythmically throughout a person's life. Chambers. The septum divides the heart lengthwise, and valves divide it crosswise. Each side of the art thus has two chambers, one above the other. A thin membrane called the endocardium lines each chamber. The top chambers, called the right atrium and left atrium, receive and collect blood returning to the heart through the veins.
After the atria (plural of atrium) have filled with blood, they contract and squeeze blood into the lower chambers, called the right ventricle and left ventricle. After the ventricles have filled, they contract and pump blood out of the heart through the arteries. The ventricles have extremely thick walls. The ventricles, which must squeeze blood from the heart, are much larger and stronger than the atria. Blood vessels. Blood enters and leaves the heart through several major vessels. Blood from the body flows into the right atrium through the body's two largest veins. The superior vena cava brings blood from the head and arms. The inferior vena cava carries blood from the trunk and legs.
It completely encloses the heart and extends above the blood vessels that emerge from the top of the heart. A slippery fluid between the epicardium and the pericardium enables the heart to contract smoothly. Heart muscle differs from the other muscles of the body--skeletal and smooth muscles. Skeletal muscles, such as those in the arms and legs, have long fibers with alternate dark and light bands called striations. We can consciously control the skeletal muscles. Smooth muscles form the walls of the stomach, intestines, and most other internal organs. The muscles lack striations, and we do not consciously control them.
They work automatically. Heart muscle has striations like skeletal muscle. But it contracts and relaxes automatically like smooth muscle. In addition, heart muscle cells act as one cell. When one heart muscle cell contracts or relaxes, the cells around it do the same. For that reason, the heart beats continuously and rhythmically throughout a person's life. Chambers. The septum divides the heart lengthwise, and valves divide it crosswise. Each side of the art thus has two chambers, one above the other. A thin membrane called the endocardium lines each chamber. The top chambers, called the right atrium and left atrium, receive and collect blood returning to the heart through the veins.
After the atria (plural of atrium) have filled with blood, they contract and squeeze blood into the lower chambers, called the right ventricle and left ventricle. After the ventricles have filled, they contract and pump blood out of the heart through the arteries. The ventricles have extremely thick walls. The ventricles, which must squeeze blood from the heart, are much larger and stronger than the atria. Blood vessels. Blood enters and leaves the heart through several major vessels. Blood from the body flows into the right atrium through the body's two largest veins. The superior vena cava brings blood from the head and arms. The inferior vena cava carries blood from the trunk and legs.
FACTS
Some of the most exciting advances in medicine have been in cardiology, the medical field that deals with diseases of the heart and blood vessels. For thousands of years, people with heart diseases did not even know they had such a problem. In the 1900's, doctors have learned to diagnose and treat certain heart conditions that once meant death. Discoveries of new drugs and the great progress in surgery have added years to the lives of many heart patients. Doctors have transplanted hearts and even developed machines that can temporarily do the work of the heart.
"The coagulation system is part of a tighly regulated pathway involving many enzymes," said Travis. "It has a so-called cascade pathway in the body, meaning that one enzyme turns on another, and then another and so forth. Normally these enzymes are present in an inactive form and are only activated when coagulation is required”. While the discovery is good news in potentially breaking the link between gum disease and heart disease, Travis said that P. gingivalis has a phenomenal ability to evade host defenses and even uses host enzymes for its own growth. In essence, it is telling the host to "kill me" and then evading the body's response and actually degrading host tissue.
Today, much research in cardiology focuses on learning about the causes of heart disease so that it can be prevented. Other research seeks to reduce death and disability from heart disease through the further development of new medicines and surgical techniques. For patients who have untreatable disorders, research continues into improving heart transplantation and producing an effective artificial heart. While periodontal disease is common in the U.S., particularly among the elderly, it is far worse in Third World countries, though its role in the development of cardiovascular disease in those countries is not yet clear.
The Human Heart is fully developed about eight weeks after conception, when the embryo is only about 1 inch (2.5 centimeters) long. The heart begins to beat even earlier--four weeks after conception, when it is just a simple tube. Ancient Egyptians believed that the heart was the center of the emotions and the intellect. An illustration from the ancient Egyptian Book of the Dead shows the god Anubis weighing a dead person's heart against a feather, the symbol of truth. The Body's Entire Supply of Blood, about 5 quarts (4.7 liters), is pumped through the body every minute. In one day, the heart pumps nearly 2,000 gallons (7,600 liters) of blood. In a 70-year lifetime, the heart pumps about 51 million gallons (193 million liters) of blood and beats 2 1/2 billion times.
"The coagulation system is part of a tighly regulated pathway involving many enzymes," said Travis. "It has a so-called cascade pathway in the body, meaning that one enzyme turns on another, and then another and so forth. Normally these enzymes are present in an inactive form and are only activated when coagulation is required”. While the discovery is good news in potentially breaking the link between gum disease and heart disease, Travis said that P. gingivalis has a phenomenal ability to evade host defenses and even uses host enzymes for its own growth. In essence, it is telling the host to "kill me" and then evading the body's response and actually degrading host tissue.
Today, much research in cardiology focuses on learning about the causes of heart disease so that it can be prevented. Other research seeks to reduce death and disability from heart disease through the further development of new medicines and surgical techniques. For patients who have untreatable disorders, research continues into improving heart transplantation and producing an effective artificial heart. While periodontal disease is common in the U.S., particularly among the elderly, it is far worse in Third World countries, though its role in the development of cardiovascular disease in those countries is not yet clear.
The Human Heart is fully developed about eight weeks after conception, when the embryo is only about 1 inch (2.5 centimeters) long. The heart begins to beat even earlier--four weeks after conception, when it is just a simple tube. Ancient Egyptians believed that the heart was the center of the emotions and the intellect. An illustration from the ancient Egyptian Book of the Dead shows the god Anubis weighing a dead person's heart against a feather, the symbol of truth. The Body's Entire Supply of Blood, about 5 quarts (4.7 liters), is pumped through the body every minute. In one day, the heart pumps nearly 2,000 gallons (7,600 liters) of blood. In a 70-year lifetime, the heart pumps about 51 million gallons (193 million liters) of blood and beats 2 1/2 billion times.
HEART OF HUMAN
Heart is the wondrous pump that powers the human body. With each heartbeat, it sends life-giving blood throughout the body. Blood carries oxygen and food to all the body cells. The rhythmic beating of the heart begins about seven months before we are born. When the heart stops beating, we die unless a special device circulates and oxygenates our blood. The heart is a large, hollow, muscular organ divided into two pumps that lie side by side. Veins transport blood from throughout the body to the right-sided pump. That pump sends the blood to the lungs, where it picks up oxygen. The oxygenated blood then flows to the left side of the heart, which pumps it through arteries to the rest of the body.
Valves control the flow of blood through the heart. The left-sided pump, which delivers blood throughout the body, is larger and stronger than the right pump. The nervous system regulates the heart and other parts of the circulatory system. A division of the nervous system, the autonomic nervous system, automatically controls the heart rate, increasing or decreasing it, depending on the body's needs. For example, the heart pumps slowly while a person sleeps, providing relatively small amounts of oxygen to the body But the heart rate can be quickly speeded up and so increase the oxygen output enormously when a person exercises, becomes frightened, or needs to fight or run.
Disease can strike any part of the heart. Disorders of the heart and blood vessels are the leading cause of death in the United States and many other countries. The most common heart disease affects the arteries that supply the heart muscle itself with blood. Disorders of those arteries usually develop over a person's lifetime. Deposits of fatty material block the arteries and so reduce the blood supply to the heart. If the heart muscle receives too little blood, it may work poorly or even die. Damage to the heart muscle resulting from a shortage of blood is called a heart attack.
"The coagulation system is part of a tighly regulated pathway involving many enzymes," said Travis. "It has a so-called cascade pathway in the body, meaning that one enzyme turns on another, and then another and so forth. Normally these enzymes are present in an inactive form and are only activated when coagulation is required”. While the discovery is good news in potentially breaking the link between gum disease and heart disease, Travis said that P. gingivalis has a phenomenal ability to evade host defenses and even uses host enzymes for its own growth. In essence, it is telling the host to "kill me" and then evading the body's response and actually degrading host tissue.
Valves control the flow of blood through the heart. The left-sided pump, which delivers blood throughout the body, is larger and stronger than the right pump. The nervous system regulates the heart and other parts of the circulatory system. A division of the nervous system, the autonomic nervous system, automatically controls the heart rate, increasing or decreasing it, depending on the body's needs. For example, the heart pumps slowly while a person sleeps, providing relatively small amounts of oxygen to the body But the heart rate can be quickly speeded up and so increase the oxygen output enormously when a person exercises, becomes frightened, or needs to fight or run.
Disease can strike any part of the heart. Disorders of the heart and blood vessels are the leading cause of death in the United States and many other countries. The most common heart disease affects the arteries that supply the heart muscle itself with blood. Disorders of those arteries usually develop over a person's lifetime. Deposits of fatty material block the arteries and so reduce the blood supply to the heart. If the heart muscle receives too little blood, it may work poorly or even die. Damage to the heart muscle resulting from a shortage of blood is called a heart attack.
"The coagulation system is part of a tighly regulated pathway involving many enzymes," said Travis. "It has a so-called cascade pathway in the body, meaning that one enzyme turns on another, and then another and so forth. Normally these enzymes are present in an inactive form and are only activated when coagulation is required”. While the discovery is good news in potentially breaking the link between gum disease and heart disease, Travis said that P. gingivalis has a phenomenal ability to evade host defenses and even uses host enzymes for its own growth. In essence, it is telling the host to "kill me" and then evading the body's response and actually degrading host tissue.
HEART DISEASE IN HUMAN
ATHENS, Ga. -- June 18, 1997 -- Scientists at the University of Georgia have discovered that an enzyme in a common bacterium is capable of activating blood-clotting in the human body. This is the first reported evidence of such an effect and may help explain the link between periodontal infections and heart disease. The new knowledge could lead to a vaccine that might neutralize the enzyme before it has a chance to activate blood-clotting and lead to cardiovascular diseases, a not uncommon occurrence in individuals with periodontitis.
"Periodontal disease is the number-one chronic infectious disease in the world," said Dr. James Travis, a professor of biochemistry and molecular biology who led the research team at UGA. "We believe it will be possible to make an inhibitor that will stop this enzyme in its tracks”. The study was published today in the the Journal of Biological Chemistry and was supported by the National Institutes of Health and by a grant from the Committee of Scientific Research in Poland.
The bacterium is known as Porphyromonas gingivalis, and it is a cause of adult periodontal disease, an infectious condition associated with a loss of connective tissue, resorption of bone and formation of infectious pockets. It is the most common cause of tooth loss in adults and is called an "opportunistic anaerobe" -- an organism living without oxygen and waiting to receive nutrition.
Though the full reason for periodontitis remains unclear, it clearly has a close relationship with P. gingivalis infections. Two similar forms of the enzymes produced by the bacterium are called gingipain Rs, and the team at UGA suspected they might be involved in causing blood clots. They also suspected an involvement with thrombin, a body chemical that cleaves a blood-plasma protein called fibrinogen into the insoluble protein referred to as a fibrin clot.
A number of studies have shown a link between mouth infections and heart disease. A report in the journal Science on April 11 revealed that in research involving 1,372 Pima Indians in Arizona, those with periodontal disease were 2.7 times as likely to suffer a heart attack as were those with healthy gums. This research, conducted by scientists at the State University of New York at Buffalo, was among the first to exclude smoking as a potential cause of gum disease, since few of the Indians in the study smoked
"Periodontal disease is the number-one chronic infectious disease in the world," said Dr. James Travis, a professor of biochemistry and molecular biology who led the research team at UGA. "We believe it will be possible to make an inhibitor that will stop this enzyme in its tracks”. The study was published today in the the Journal of Biological Chemistry and was supported by the National Institutes of Health and by a grant from the Committee of Scientific Research in Poland.
The bacterium is known as Porphyromonas gingivalis, and it is a cause of adult periodontal disease, an infectious condition associated with a loss of connective tissue, resorption of bone and formation of infectious pockets. It is the most common cause of tooth loss in adults and is called an "opportunistic anaerobe" -- an organism living without oxygen and waiting to receive nutrition.
Though the full reason for periodontitis remains unclear, it clearly has a close relationship with P. gingivalis infections. Two similar forms of the enzymes produced by the bacterium are called gingipain Rs, and the team at UGA suspected they might be involved in causing blood clots. They also suspected an involvement with thrombin, a body chemical that cleaves a blood-plasma protein called fibrinogen into the insoluble protein referred to as a fibrin clot.
A number of studies have shown a link between mouth infections and heart disease. A report in the journal Science on April 11 revealed that in research involving 1,372 Pima Indians in Arizona, those with periodontal disease were 2.7 times as likely to suffer a heart attack as were those with healthy gums. This research, conducted by scientists at the State University of New York at Buffalo, was among the first to exclude smoking as a potential cause of gum disease, since few of the Indians in the study smoked
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