An Overview of Heart Anatomy and Function
The primary role of the heart is to pump deoxygenated blood from the body to the lungs, where it picks up oxygen and drops off carbon dioxide, and then to return the newly oxygenated blood to the body.
The human heart is comprised of four chambers, the right atrium, right ventricle, left atrium and left ventricle. The heart can be described as having two sides – the right side and the left side, each functioning as a separate pump. The right side of the heart propels blood into the pulmonary circulation while the left side of the heart sends it into systemic circulation.
The heart receives deoxygenated blood from the upper body via the superior vena cava and from the lower body via the inferior vena cava. These two veins join together to return the deoxygenated blood to the right atrium. The right atrium is separated from the right ventricle by an atrioventricular valve, also known as the tricuspid valve, which ensures that blood only flows in one direction. The blood from the right ventricle is then sent into the lungs where it picks up oxygen.
Upon returning to the left atrium, fully oxygenated, the blood flows past the left atrioventricular valve, which also goes by the names mitral valve or bicuspid valve, and into the left ventricle. Finally, the blood from the left ventricle is returned to the systemic circulation via the aorta, the largest artery of the body.
The pressures associated with the filling and emptying of the heart’s ventricles are referred to as diastole and systole. Diastole is the pressure measured in the arterial system when the ventricles are relaxed and filling with blood. Systole is the pressure associated with ventricular contraction, when the blood is being pushed into the systemic and pulmonary circulations. The 120 is the systole and the 80 is the diastole in a 120/80 blood pressure.
The heart can vary the speed of its contractions based on feedback it receives from the body and brain. When the body requires more oxygen, such as during exercise, when frightened, or any other time the sympathetic nervous system is activated, the heart increases its rate of contraction. When the heart receives the message that the body needs more oxygen it begins beating faster and increases the heart rate. Conversely, when the parasympathetic nervous system is activated, such as during times of rest, the heart rate slows down.
The heart has an internal electrical system which causes the heart to contract and relax over 100,000 times a day depending on the person and activity level. This electrical system begins at the sinoatrial node (SA node), located in the right heart, and quickly causes the contraction of both atria (left and right). The action potential which is generated, travels to a second node called the AV, or atrioventricular node. When the AV node is activated it causes a series of steps to occur resulting in the contraction of the ventricles. There is a slight delay between the contraction of the atria and the contraction of the ventricles. This allows the filling of the ventricles before they contract to propel the blood into the pulmonary and systemic circulations. The entire process of atrial and ventricular contraction is approximately two-tenths of a second from start to end.
When an individual listens to the heart through a stethoscope or through the chest wall, they will hear two beats. These are referred to as S1 and S2 and correspond to the closing of the valves between the atria and ventricles and also the valves which are found at the opening to the pulmonary artery and aorta.
Heart Disease
Heart disease can be found in approximately 1 out of every 12 Americans, according to the statistics reported by the Centers for Disease Control and Prevention. That is a grand total of 22 million adults nationwide battling this disease on a daily basis. In the US, heart disease is the number one killer of men and women. That being said, this is an extremely important topic to understand and can be prevented from happening to you.
The term heart disease is a broad definition providing a large canopy for numerous other diseases. A quick list shows heart disease to include coronary artery disease (heart attacks fall in this field), arrhythmias, heart failure, congenital heart disease, heart valve and muscle disease and vascular disease (disease of the blood vessel). This is not an all- inclusive list, rather it only lists the more commonly encountered types of heart disease. Each has its own signs, symptoms, causes and treatments. However, there are certain steps that people can take to minimize their risk of developing heart disease.
In general, to decrease the possibility of acquiring heart disease, the following should be adhered to: stop smoking, lower levels of bad cholesterol (LDL) and increase levels of good cholesterol (HDL), prevent high blood pressure, increase regular physical activity level, keep body weight within the recognized “safe” zones, manage any diabetes that may be present and keep stress and anger levels to a minimum. Many of these controllable risk factors can be managed through a change in lifestyle. Lifestyle changes must be implemented through diet, exercise and stress management.
With these guidelines in mind, there are also several uncontrollable risk factors that may contribute to heart disease: males have a higher risk than women of being diagnosed with heart disease, with age a person’s risk increases, women after menopause are more susceptible, and those with a family history have a greater risk. Although uncontrollable, these risk factors do no point toward the eminent development of heart disease. By keeping the controllable risk factors in check, heart disease can be prevented most of the time.
Symptoms of heart disease are varied depending on the type of disease. Symptoms may be present at birth, as in those born with a congenital heart defect. Others are acquired through lifestyle and may not show symptoms until much later in life. The most commonly known type of heart disease is the heart attack or coronary artery disease. Heart attacks afflict more than 1.5 million Americans each year. The frightening thing about heart attacks is its silent warning signs. Most people don’t know they have coronary artery disease (a narrowing of the arteries that feed the heart) until a heart attack strikes. The statistics show that approximately one third of heart attack sufferers will die from the attack.
Prevention seems to be the key for keeping our “tickers” healthy and fit. However, for those suffering from heart disease, new research and clinical trials are constantly being turned out and tried. Most heart disease problems are now managed through simultaneous lifestyle changes and medication. Additionally, new treatment modalities and plans are surfacing as improvements are made in the fields of transplantation, surgical operations and stem-cell research.
