heart
[hahrt]the hollow muscular organ lying slightly to the left of the midline of the chest. The heart serves as a pump controlling the blood flow in two circuits, the pulmonary and the systemic. See also circulatory system, and see Plates.
Divisions of the Heart. The septum, a thick muscular wall, divides the heart into right and left halves. Each half is again divided into upper and lower quarters or chambers. The lower chambers are called ventricles and the upper chambers are called atria. The right side of the heart, consisting of the right atrium and right ventricle, receives deoxygenated blood and sends it into the pulmonary circuit. The left side, consisting of the left atrium and left ventricle, receives oxygenated blood and sends it into the systemic circuit.
Valves of the Heart. The atrioventricular valves connect an atrium and a ventricle: between the right atrium and right ventricle is the tricuspid valve and between the left atrium and left ventricle is the mitral valve. The semilunar valves are valves at the blood's exit points from the heart: the pulmonary valve opens from the right ventricle into the pulmonary artery, and the aortic valve opens from the left ventricle into the aorta. These valves, both within the heart and leading out of it, open and shut in such a way as to keep the blood flowing in one direction through the heart's two separate pairs of chambers: fro atrium to ventricle and out through its appropriate artery.
Layers of the Heart. The heart wall is composed of three layers of tissues. Its chambers are lined by a delicate membrane, the endocardium. The thick muscular wall essential to normal pumping action of the heart is called the myocardium. The thin but sturdy membranous sac surrounding the exterior of the heart is called the pericardium.
The Heart's Pacemaker. The heart is made up of special muscle tissue, capable of continuous rhythmic contraction without tiring. The impulse that starts the contraction of the heart has its origin in an area of the right atrium called the sinoatrial node; it is this special tissue that acts as the normal pacemaker for the heart. The impulse is transmitted in a fraction of a second through the atria to another group of similarly sensitive fibers called the atrioventricular node, through the bundle of his, down the bundle branches, and to the Purkinje fibers, resulting in contraction of the ventricles.
Pumping Action. Although the right and left sides of the heart serve two separate branches of the circulation, each with its distinct function, they are coordinated so that the heart efficiently serves both sides with a single pumping action. The valve action on both sides is also coordinated with the two phases of the pumping action. Thus during diastole, the relaxation phase, oxygen-poor blood returning from the systemic circulation and accumulated in the right atrium pours into the right ventricle. At the same time, the oxygen-rich blood that has accumulated in the left atrium returning from the pulmonary circulation pours into the left ventricle. The walls of both atria contract to press blood into the relaxed ventricles. In the next contraction phase (systole), the valves between the atria and ventricles close and the ventricles contract, forcing the blood through the pulmonary artery and the aorta. At the end of the contraction the pulmonary and aortic valves snap shut, preventing any backward flow of the blood into the ventricles. Diastole follows, the ventricles again filling with the blood from their respective atria, and the cycle is repeated.
Disorders of the Heart. The heart is subject to a variety of disorders. Among them are congenital heart defects, which begin or exist at the time of birth. Disorders of this nature may interfere with the flow of the blood both within the heart and from the heart to the lungs. tetralogy of fallot and patent ductus arteriosus are examples of congenital heart defects. Rheumatic heart disease may be associated with rheumatic fever. Other disorders of the heart include angina pectoris, which is caused by coronary insufficiency; myocardial infarction, which results from formation of a blood clot in a coronary artery and death of myocardial tissue; and heart failure. Cardiac arrhythmias are disturbances in the normal rate and rhythm of the heartbeat.
Diagnostic Tests. Many different diagnostic procedures are available for the examination of the heart. Along with a history and physical examination, an electrocardiogram (ECG) is routinely obtained. It shows a tracing of the electrical excitation that spreads through the heart during each beat. It is the definitive source of information about cardiac arrhythmias, and also gives diagnostic information about myocardial infarctions.
Exercise stress testing is a valuable tool for detecting persons who have some degree of coronary heart disease. The test subject performs maximal exercise while being monitored by ECG. A positive stress test occurs when the subject cannot sustain the exercise for the duration of the test, cannot attain a normal maximal heart rate, or shows ECG changes indicative of ischemia. When stress testing is used for screening purposes, it is not diagnostic. However, persons with a positive stress test are 13 times more likely to develop significant coronary artery or heart disease and should work to reduce their risk factors. Stress testing is also used to evaluate the severity of known coronary disease and to guide the rehabilitation of a patient with coronary disease.
Phonocardiography is the recording of heart sounds and murmurs. It is more precise than auscultation with a stethoscope because it provides a permanent visual record that can be used to obtain precise timing information and can be used as baseline data for comparison with later findings.
Echocardiography is a type of diagnostic ultrasonography that provides information about the structure and function of the heart. It is a comfortable technique for the patient and is capable of establishing a diagnosis for several types of heart disease, especially those involving the valves. Types include M-mode, Doppler, and transesophageal echocardiography.
Several types of radioisotope examination are used to detect heart disease. A radioisotope imaging agent is injected into the patient, and a scintillation camera is then used to make an image of the distribution of radioactivity.
Thallium 201 has an affinity for heart tissue; when injected intravenously, it is carried to areas with adequate perfusion. Myocardial infarcts and areas of acute ischemia or scarring appear as “cold spots” (areas of no uptake of thallium) on the scintigram. When the isotope is injected during maximal exercise in an exercise stress test, the scan shows areas of inadequate perfusion and is a better indicator of coronary disease than a stress test alone.
Radiopharmaceuticals that label the blood pool can be used with a computerized scintillation camera to evaluate ventricular performance. Images of the first pass of the radioisotope through the heart can be used to determine the cardiac output and ejection fraction, the size of the ventricles, and regional wall motion.
The imaging agents used for bone scans, such as technetium 99m pyrophosphate or diphosphonate, also have an affinity for areas of acute ischemic tissue damage. “Hot spots” on the scintigram (areas of isotope uptake) show areas of acute infarction. The scan is usually negative by approximately 6 days after an infarction.
Cardiac catheterization is an invasive technique used when definitive data are required to decide whether heart disease should be treated medically, surgically, or through interventional cardiology techniques such as percutaneous transluminal angioplasty, stents, or valvuloplasty. A catheter is inserted into a vein or artery, usually the brachial artery or the femoral vein or artery, and guided into the heart. Tracings of the pressure pulses within the chambers during the heart cycle are obtained. Cardiac output, pulmonary artery pressures, the orifice area of valves, and the degree of left-to-right shunting can be determined.
Angiocardiography is the x-ray examination of the heart after injection of a radiopaque contrast medium through a catheter at various locations in the heart. The films show the size and motion of the heart chambers and can demonstrate aortic or mitral regurgitation. In coronary arteriography the contrast medium is injected through a catheter into the orifice of each coronary artery. The films show atherosclerotic obstructions of the arteries and are useful in planning coronary bypass surgery, percutaneous transluminal angioplasty, or stents.
Exercise stress testing is a valuable tool for detecting persons who have some degree of coronary heart disease. The test subject performs maximal exercise while being monitored by ECG. A positive stress test occurs when the subject cannot sustain the exercise for the duration of the test, cannot attain a normal maximal heart rate, or shows ECG changes indicative of ischemia. When stress testing is used for screening purposes, it is not diagnostic. However, persons with a positive stress test are 13 times more likely to develop significant coronary artery or heart disease and should work to reduce their risk factors. Stress testing is also used to evaluate the severity of known coronary disease and to guide the rehabilitation of a patient with coronary disease.
Phonocardiography is the recording of heart sounds and murmurs. It is more precise than auscultation with a stethoscope because it provides a permanent visual record that can be used to obtain precise timing information and can be used as baseline data for comparison with later findings.
Echocardiography is a type of diagnostic ultrasonography that provides information about the structure and function of the heart. It is a comfortable technique for the patient and is capable of establishing a diagnosis for several types of heart disease, especially those involving the valves. Types include M-mode, Doppler, and transesophageal echocardiography.
Several types of radioisotope examination are used to detect heart disease. A radioisotope imaging agent is injected into the patient, and a scintillation camera is then used to make an image of the distribution of radioactivity.
Thallium 201 has an affinity for heart tissue; when injected intravenously, it is carried to areas with adequate perfusion. Myocardial infarcts and areas of acute ischemia or scarring appear as “cold spots” (areas of no uptake of thallium) on the scintigram. When the isotope is injected during maximal exercise in an exercise stress test, the scan shows areas of inadequate perfusion and is a better indicator of coronary disease than a stress test alone.
Radiopharmaceuticals that label the blood pool can be used with a computerized scintillation camera to evaluate ventricular performance. Images of the first pass of the radioisotope through the heart can be used to determine the cardiac output and ejection fraction, the size of the ventricles, and regional wall motion.
The imaging agents used for bone scans, such as technetium 99m pyrophosphate or diphosphonate, also have an affinity for areas of acute ischemic tissue damage. “Hot spots” on the scintigram (areas of isotope uptake) show areas of acute infarction. The scan is usually negative by approximately 6 days after an infarction.
Cardiac catheterization is an invasive technique used when definitive data are required to decide whether heart disease should be treated medically, surgically, or through interventional cardiology techniques such as percutaneous transluminal angioplasty, stents, or valvuloplasty. A catheter is inserted into a vein or artery, usually the brachial artery or the femoral vein or artery, and guided into the heart. Tracings of the pressure pulses within the chambers during the heart cycle are obtained. Cardiac output, pulmonary artery pressures, the orifice area of valves, and the degree of left-to-right shunting can be determined.
Angiocardiography is the x-ray examination of the heart after injection of a radiopaque contrast medium through a catheter at various locations in the heart. The films show the size and motion of the heart chambers and can demonstrate aortic or mitral regurgitation. In coronary arteriography the contrast medium is injected through a catheter into the orifice of each coronary artery. The films show atherosclerotic obstructions of the arteries and are useful in planning coronary bypass surgery, percutaneous transluminal angioplasty, or stents.
Prevention of Heart Disease. Although heart disease remains the leading cause of death in industrialized countries, its mortality rate has steadily declined since the early 1970s. A major factor in this decline is the development of more effective preventive measures and modes of treatment for ischemic heart disease. These advances include open heart surgery to repair congenital defects and replace malfunctioning valves; vascular surgery to repair or bypass obstructions in the coronary arteries and aorta; newer and more accurate diagnostic tests and procedures for detecting problems involving the heart and blood vessels; antimicrobial therapy for the treatment of rheumatic fever, syphilis, and other infectious diseases that are damaging to the heart; more sophisticated monitoring equipment and intensive care units; and aggressive medical treatment and management of heart disease and hypertension.
All these contributions to the control and correction of cardiovascular diseases are important in the reduction of mortality rates and improvement in patients' quality of life. Nevertheless, it is also important for prevention that there be an improvement of the general public's awareness of the causes and risk factors of cardiac disorders. Major risk factors that can be avoided, modified, or corrected include cigarette smoking, elevated blood lipids, obesity, habitual dietary excesses, lack of exercise, hypertension, and excessive stress. Health professionals can promote reduction in the incidence of heart disease by educating the public about these risk factors and by encouraging active participation in preventive measures, particularly in those that involve changes in lifestyle.
All these contributions to the control and correction of cardiovascular diseases are important in the reduction of mortality rates and improvement in patients' quality of life. Nevertheless, it is also important for prevention that there be an improvement of the general public's awareness of the causes and risk factors of cardiac disorders. Major risk factors that can be avoided, modified, or corrected include cigarette smoking, elevated blood lipids, obesity, habitual dietary excesses, lack of exercise, hypertension, and excessive stress. Health professionals can promote reduction in the incidence of heart disease by educating the public about these risk factors and by encouraging active participation in preventive measures, particularly in those that involve changes in lifestyle.
Blood enters the right atrium from the body and then passes into the right ventricle, where it is pumped into the lungs. It returns from the lungs into the right atrium. It enters the left ventricle and then is pumped to the body via the aorta.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
heart
(hart), [TA]A hollow muscular organ that receives the blood from the veins and propels it into the arteries. In mammals it is divided by a musculomembranous septum into two halves-right or venous and left or arterial-each of which consists of a receiving chamber (atrium) and an ejecting chamber (ventricle).
[A.S. heorte]
Farlex Partner Medical Dictionary © Farlex 2012
heart
(härt)n.
1. The chambered muscular organ in vertebrates that pumps blood received from the veins into the arteries, thereby maintaining the flow of blood through the entire circulatory system. In humans it has four chambers.
2. A similarly functioning structure in invertebrates.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
heart
See Abiomed implantable heart, Athlete's heart, Baby Fae heart, Bleeding heart, Crisscross heart, Dextroposition heart, Depraved heart, Egg-shaped heart, Flabby heart, Flask-shaped heart, Holiday heart, Left heart, Mongolian heart, Old soldier's heart, Penn State heart, Right heart, Sabot heart, Second heart, Stone heart, Swinging heart, Water bottle heart.HEART
Cardiology A clinical trial–Healing & Early Afterload Reducing TherapyMcGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
heart
(hahrt) [TA]A hollow muscular organ that receives the blood from the veins and propels it into the arteries. It is divided by a musculomembranous septum into two halves (right or venous and left or arterial) each of which consists of a receiving chamber (atrium) and an ejecting chamber (ventricle).
Synonym(s): cor [TA] , coeur.
Synonym(s): cor [TA] , coeur.
[A.S. heorte]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
heart
The twin-sided, four-chambered controlled muscular pump that, by means of regular rhythmical tightening (contractions) of the chambers and the action of valves, maintains the twin circulations of blood to the lungs and to the rest of the body. The right side of the heart pumps blood through the lungs and back to the left side. The left side pumps the blood returning from the lungs through all parts of the body and back to the right side.Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
)
Fig. 189 Heart . Nerve centres in the mammalian heart.
heart
the muscular pump of the BLOOD CIRCULATORY SYSTEM. In those invertebrates that possess a heart (e.g. ARTHROPODS, ANNELIDS, MOLLUSCS, ECHINODERMS) the heart is composed of several chambers and lies dorsal to the gut. In vertebrates the heart is made of special CARDIAC MUSCLE and lies in a ventral position surrounded by the PERICARDIUM. The five classes of vertebrates show an increasing complexity of structure, from the simple S-shaped heart with one ATRIUM and one VENTRICLE (2) found in fish, through the amphibians and most reptiles where the heart is divided into two atria but retains a single ventricle, and on to the birds and mammals where the heart shows complex separation into two sides with two atria and two ventricles. The main features of the human heart are:- the right side pumps blood around the pulmonary (lung) circulation for oxygenation, the left side pumping blood around the systemic (body) circulation where it becomes deoxygenated.
- blood from the body enters the right atrium via the superior vena cava (upper body) and inferior vena cava (lower body). A coronary sinus also drains into the right atrium bringing blood from the heart itself. The right atrium squeezes blood through the atrioventricular (AV) opening into the muscular right ventricle. finally, blood is ejected into the single opening of the pulmonary artery which splits to go to the two lungs.
- blood enters the left atrium from four pulmonary veins and passes through the left AV opening into the left ventricle. This has a much thicker wall than the right ventricle, reflecting its requirement for greater power. Blood leaves the left ventricle by one great vessel, the AORTA, which supplies all parts of the body, including the heart.
- flow of blood through the heart is in one direction only, due to the presence of various valves. Back-flow from ventricles to atria is prevented by AV valves, the tricuspid valve on the right side with three flaps, and the BICUSPID (3) valve on the left side with two flaps, both valves held in place by cords of connective tissue, the ‘chordae tendinae’. Back-flow from arteries to the ventricles is prevented by semilunar valves.
- various nerve areas connected with contraction are located in the heart (see HEART, CARDIAC CYCLE): (i) the sinoatrial node (SAN) or ‘pacemaker’ located in the wall of the right atrium near the entry of the venae cavae; (ii) the atrioventricular node (AVN) at the junction of all four heart chambers; (iii) the atrioventricular bundle, or bundle of His, running down the interventricular septum from the AVN; and (iv) a network of Purkinje tissue and other fibres spreading out from the bundle of His across the walls of both ventricles. See Fig. 189 .
Other nerve areas are situated in or near the heart: (i) baroreceptors in the walls of the heart, in the aortic arch, the carotid sinus, venae cavae and pulmonary veins where they enter the atria. Such sensory receptors are stimulated by stretching of the structure in which they are found, resulting in a decrease in blood pressure. (ii) chemoreceptors sensitive to blood CO2 levels are found in the AORTIC BODY and CAROTID BODY.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
heart
(hahrt) [TA]Hollow muscular organ that receives blood from veins and propels it into the arteries. In mammals, divided by a musculomembranous septum into two halves-right or venous and left or arterial-each of which consists of a receiving chamber (atrium) and an ejecting chamber (ventricle).
[A.S. heorte]
Medical Dictionary for the Dental Professions © Farlex 2012
Patient discussion about heart
Q. how does it feel to heart promblems answer to my question then talk to me
A. Heart problems may manifest as sensation of the heartbeats (called palpitations, as with rhythm problems), chest pain (usually a feeling of tightness or pressure in the chest rather than frank pain), or difficulty breathing (called dyspnea).
Other manifestations may include fainting (called syncope) either spontaneously or after exercise, edema (swelling) of the legs and various other non specific complaints.
The manifestations depend, of course, on the specific disease and the various characteristics of the patient (age, sex etc.)
You may read more here:
www.nlm.nih.gov/medlineplus/heartdiseases.html
Other manifestations may include fainting (called syncope) either spontaneously or after exercise, edema (swelling) of the legs and various other non specific complaints.
The manifestations depend, of course, on the specific disease and the various characteristics of the patient (age, sex etc.)
You may read more here:
www.nlm.nih.gov/medlineplus/heartdiseases.html
Q. What happens to my heart when I exercise? My senior told me that exercise is good for health and especially for heart. What happens to my heart when I exercise?
A. the heart is a muscle that constructs and pump blood through our body. like any muscle it can get bigger and stronger. doing exercise is putting pressure on the heart and the heart start to react by growing.
Q. Is garlic helpful in heart ailments? I have heard that garlic is very good for cardiac health and using in curries or cooked with foods will be helpful. I have also heard that it has anti-inflammatory substances and also helps in weight loss. Is garlic helpful in heart ailments?
A. It acts as antioxidant and reduces the amount of free radicals in your body. It’s helpful once taken raw. But the raw garlic can cause bad breadth and blistering of skin and diarrhea. So, there should be a reduced intake of raw garlic. It’s better to have garlic in a cooked up form like in curries or with vegetables. This will also give the desired benefits of garlic and the side effect of over consumption of garlic will also be reduced.
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