Health and care topics

Anatomy of the heart The atria: These are the two upper chambers, which receive blood. The ventricles: These are the two lower chambers, which discharge blood. A wall of tissue called the septum separates the left and right atria and the left and right ventricle. Valves separate the atria from the ventricles. The heart’s walls consist of three layers of tissue: Myocardium: This is the muscular tissue of the heart. Endocardium: This tissue lines the inside of the heart and protects the valves and chambers. Pericardium: This is a thin protective coating that surrounds the other parts. Epicardium: This protective layer consists mostly of connective tissue and forms the innermost layer of the pericardium. How the heart works The rate at which the heart contracts depends on many factors, such as: activity and exercise emotional factors some medical conditions a fever some medications dehydration At rest, the heart might beat around 60 times each minute. But this can increase to 100 beats per minute (bpm) or more.Left and right sides The left and right sides of the heart work in unison. The atria and ventricles contract and relax in turn, producing a rhythmic heartbeat. Right side The right side of the heart receives deoxygenated blood and sends it to the lungs. The right atrium receives deoxygenated blood from the body through veins called the superior and inferior vena cava. These are the largest veins in the body. The right atrium contracts, and blood passes to the right ventricle. Once the right ventricle is full, it contracts and pumps the blood to the lungs via the pulmonary artery. In the lungs, the blood picks up oxygen and offloads carbon dioxide. Left side The left side of the heart receives blood from the lungs and pumps it to the rest of the body. Newly oxygenated blood returns to the left atrium via the pulmonary veins. The left atrium contracts, pushing the blood into the left ventricle. Once the left ventricle is full, it contracts and pushes the blood back out to the body via the aorta. Diastole, systole, and blood pressure Each heartbeat has two parts: Diastole: The ventricles relax and fill with blood as the atria contract, emptying all blood into the ventricles. Systole: The ventricles contract and pump blood out of the heart as the atria relax, filling with blood again. When a person takes their blood pressure, the machine will give a high and a low numberTrusted Source. The high number is the systolic blood pressure, and the lower number is the diastolic blood pressure. Systolic pressure: This shows how much pressure the blood creates against the artery walls during systole. Diastolic pressure: This shows how much pressure is in the arteries during diastole. Gas exchange When blood travels through the pulmonary artery to the lungs, it passes through tiny capillaries that connect on the surface of the lung’s air sacs, called the alveoli. The body’s cells need oxygen to function, and they produce carbon dioxide as a waste product. The heart enables the body to eliminate the unwanted carbon dioxide. Oxygen enters the blood and carbon dioxide leaves it through the capillaries of the alveoli. The coronary arteries on the surface of the heart supply oxygenated blood to the heart muscle. Pulse A person can feel their pulse at points where arteries pass close to the skin’s surface, such as on the wrist or neck. The pulse is the same as the heart rate. When you feel your pulse, you feel the rush of blood as the heart pumps it through the body. A healthy pulse is usually 60–100 bpmTrusted Source, and what is normal can vary from person to person. A very active person may have a pulse as low as 40 bpm. People with a larger body size tend to have a faster pulse, but it is not usually over 100 bpm. Valves Aortic valve: This is between the left ventricle and the aorta. Mitral valve: This is between the left atrium and the left ventricle. Pulmonary valve: This is between the right ventricle and the pulmonary artery. Tricuspid valve: This is between the right atrium and right ventricle. Most people are familiar with the sound of the heart. In fact, the heart makes many types of soundTrusted Source, and doctors can distinguish these to monitor the health of the heart. The opening and closing of the valves are key contributors to the sound of the heartbeat. If there is leaking or a blockage of the heart valves, it can create sounds called “murmurs.” The heart’s electrical system To pump blood throughout the body, the muscles of the heart must work together to squeeze the blood in the right direction, at the right time, and with the right force. Electrical impulses coordinate this activity. The electrical signal begins at the sino-atrial node, sometimes called the sinus, or SA, node. This is the heart’s pacemaker, and it sits at the top of the right atrium. The signal causes the atria to contract, pushing blood down into the ventricles. The electrical impulse then travels to an area of cells at the bottom of the right atrium, between the atria and ventricles, called the atrioventricular, or AV, node. These cells act as a gatekeeper. They coordinate the signal so that the atria and ventricles do not contract at the same time. There needs to be a slight delay. From here, the signal travels along fibers, called Purkinje fibers, within the ventricle walls. The fibers pass the impulse to the heart muscle, causing the ventricles to contract. Blood vessels There are three types of blood vessels: Arteries: These carry oxygenated blood from the heart to the rest of the body. The arteries are strong, muscular, and stretchy, which helps push blood through the circulatory system, and they also help regulate blood pressure. The arteries branch into smaller vessels called arterioles. Veins: These carry deoxygenated blood back to the heart, and they increase in size as they get closer to the heart. Veins have thinner walls than arteries. Capillaries: These connect the smallest arteries to the smallest veins. They have very thin walls, which allow them to exchange compounds such as carbon dioxide, water, oxygen, waste, and nutrients with surrounding tissues. The heart, blood, and blood vessels make up the circulatory, or cardiovascular, system. Cardiac arrest: When the heart stops The heart is essential to life — if it stops beating, blood will not reach the brain and other organs, and the person can die within minutesTrusted Source. This is called cardiac arrest. If a person experiences cardiac arrest, they will be unable to speak or breathe, and they will have no heartbeat. Anyone nearby should call 911 immediately and start cardiopulmonary resuscitation (CPR), pressing hard and fast with locked hands on the center of the person’s chest. According to the Centers for Disease Control and Prevention (CDC), CPR can double or triple a person’s chance of survival after their heart stops.Heart Conditions Coronary artery disease: Over the years, cholesterol plaques can narrow the arteries supplying blood to the heart. The narrowed arteries are at higher risk for complete blockage from a sudden blood clot (this blockage is called a heart attack). Stable angina pectoris: Narrowed coronary arteries cause predictable chest pain or discomfort with exertion. The blockages prevent the heart from receiving the extra oxygen needed for strenuous activity. Symptoms typically get better with rest. Unstable angina pectoris: Chest pain or discomfort that is new, worsening, or occurs at rest. This is an emergency situation as it can precede a heart attack, serious abnormal heart rhythm, or cardiac arrest. Myocardial infarction (heart attack): A coronary artery is suddenly blocked. Starved of oxygen, part of the heart muscle dies. Arrhythmia (dysrhythmia): An abnormal heart rhythm due to changes in the conduction of electrical impulses through the heart. Some arrhythmias are benign, but others are life-threatening. Congestive heart failure: The heart is either too weak or too stiff to effectively pump blood through the body. Shortness of breath and leg swelling are common symptoms. Cardiomyopathy: A disease of heart muscle in which the heart is abnormally enlarged, thickened, and/or stiffened. As a result, the heart's ability to pump blood is weakened. Myocarditis: Inflammation of the heart muscle, most often due to a viral infection. Pericarditis: Inflammation of the lining of the heart (pericardium). Viral infections, kidney failure, and autoimmune conditions are common causes. Pericardial effusion: Fluid between the lining of the heart (pericardium) and the heart itself. Often, this is due to pericarditis. Atrial fibrillation: Abnormal electrical impulses in the atria cause an irregular heartbeat. Atrial fibrillation is one of the most common arrhythmias. Pulmonary embolism: Typically a blood clot travels through the heart to the lungs. Heart valve disease: There are four heart valves, and each can develop problems. If severe, valve disease can cause congestive heart failure. Heart murmur: An abnormal sound heard when listening to the heart with a stethoscope. Some heart murmurs are benign; others suggest heart disease. Endocarditis: Inflammation of the inner lining or heart valves of the heart. Usually, endocarditis is due to a serious infection of the heart valves. Mitral valve prolapse: The mitral valve is forced backward slightly after blood has passed through the valve. Sudden cardiac death: Death caused by a sudden loss of heart function (cardiac arrest). Cardiac arrest: Sudden loss of heart function.

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