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 Heart: How the Heart Works Main Article |  Glossary |  Heart: How the Heart Works Index 

How the Heart Works Glossary of Terms

The following are health and medical definitions of terms that appear in the How the Heart Works article.

Abdomen: The belly , that part of the body that contains all of the structures between the chest and the pelvis . The abdomen is separated anatomically from the chest by the diaphragm , the powerful muscle spanning the body cavity below the lungs .
See the entire definition of Abdomen

Annulus: A ringlike structure, or any body part that is shaped like a ring. Applied to many small ring-shaped structures.
See the entire definition of Annulus

Anterior: The front, as opposed to the posterior. The anterior surface of the heart is toward the breast bone (the sternum).
See the entire definition of Anterior

Aorta: The largest artery in the body, the aorta arises from the left ventricle of the heart, goes up (ascends) a little ways, bends over (arches), then goes down (descends) through the chest and through the abdomen to where ends by dividing into two arteries called the common iliac arteries that go to the legs.
See the entire definition of Aorta

Aortic: Pertaining to the aorta , the largest artery in the body.
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Aortic valve: One of the four valves in the heart, this valve is situated at exit of the left ventricle of the heart where the aorta (the largest of all arteries) begins.
See the entire definition of Aortic valve

Arms: An appendage in anatomy and in clinical trials. See: Arm.

Artery: A vessel that carries blood high in oxygen content away from the heart to the farthest reaches of the body. Since blood in arteries is usually full of oxygen, the hemoglobin in the red blood cells is oxygenated. The resultant form of hemoglobin (oxyhemoglobin) is what makes arterial blood look bright red.
See the entire definition of Artery

Atria: The plural of atrium. The atria are the two smaller chambers of the heart. Each atrium consists of an open space with recessed walls.
See the entire definition of Atria

Atrioventricular node: The atrioventricular (AV) node is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass through the AV node to reach the ventricles.
See the entire definition of Atrioventricular node

Atrium: One of the two smaller chambers of the heart. Each atrium consists of an open space with recessed walls. The plural of atrium is atria.
See the entire definition of Atrium

AV node: An electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass through the AV node to reach the ventricles.
See the entire definition of AV node

Blood: The familiar red fluid in the body that contains white and red blood cells, platelets, proteins, and other elements. The blood is transported throughout the body by the circulatory system. Blood functions in two directions: arterial and venous. Arterial blood is the means by which oxygen and nutrients are transported to tissues while venous blood is the means by which carbon dioxide and metabolic by-products are transported to the lungs and kidneys, respectively, for removal from the body.

Capillaries: Capillaries are the smallest of blood vessels. They serve to distribute oxygenated blood from arteries to the tissues of the body and to feed deoxygenated blood from the tissues back into the veins. The capillaries are thus a central component in the circulatory system, essentially between the arteries and the veins. When pink areas of skin are compressed, this causes blanching because blood is pressed out of the capillaries. The blood is the fluid in the body that contains, among other elements, the red blood cells (erythrocytes) that carry the oxygen and give the blood its red color.

Capillary: One of the tiny blood vessels that connect the arterioles (the smallest divisions of the arteries) and the venules (the smallest divisions of the veins). The capillaries form a fine network in many parts of the body.
See the entire definition of Capillary back to top

Carbon dioxide: A gas which is the byproduct of cellular metabolism and which collects in the tissues, is cleared from the tissues by the blood within the veins, is carried by the hemoglobin in the red blood cells, and removed from the body via the lungs in the exhaled air. Abbreviated CO2.

Chordae tendineae: Thread-like bands of fibrous tissue which attach on one end to the edges of the tricuspid and mitral valves of the heart and on the other end to the papillary muscles, small muscles within the heart that serve to anchor the valves.

Circulation: The movement of fluid in a regular or circuitous course. Although the noun "circulation" does not necessarily refer to the circulation of the blood, for all practical purposes today it does. Heart failure is an example of a problem with the circulation.

Circulatory: Having to do with the circulation, the movement of fluid in a regular or circuitous course. Although the adjective "circulatory" need not necessarily refer to the circulation of the blood, for all practical purposes today it does. A circulatory problem is taken usually to be a problem with the blood circulation, for example with heart failure.
See the entire definition of Circulatory

Circulatory system: The system that moves blood throughout the body. The circulatory system is composed of the heart, arteries, capillaries, and veins. This remarkable system transports oxygenated blood from the lungs and heart throughout the body via the arteries. The blood goes through the capillaries which are situated between the arteries and veins. And the blood that has been depleted of oxygen by the body is then returned to the lungs and heart via the veins.

Circumflex: Curved like a bow. In anatomy, circumflex describes a structure that bends around like a bow. For example, the circumflex branch of the left coronary artery.
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Cluster: In epidemiology, an aggregation of cases of a disease or another health-related condition, such as a cancer or birth defect, closely grouped in time and place. The number of cases in the cluster may or may not exceed the expected number. This is determined by cluster analysis, a set of statistical methods used to analyze clusters.

Collateral: In anatomy, a collateral is a subordinate or accessory part. A collateral is also a side branch, as of a blood vessel or nerve.
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Coronary arteries: The vessels that supply the heart muscle with blood rich in oxygen. They are called the coronary arteries because they encircle the heart in the manner of a crown. The word "coronary" comes from the Latin "corona" and Greek "koron" meaning crown. Like other arteries, the coronaries may be subject to arteriosclerosis (hardening of the arteries). There are a number of coronary arteries. Those most often bypassed today include the right coronary artery, the posterior descending coronary artery, the left main coronary artery, the left anterior descending coronary artery and the left circumflex coronary artery. Plaques obstructing the coronary arteries may also be treated by balloon angioplasty , stents, and other techniques.
See the entire definition of Coronary arteries

Coronary artery disease: A major cause of illness and death, coronary artery disease (CAD) begins when hard cholesterol substances (plaques) are deposited within a coronary artery.
See the entire definition of Coronary artery disease

Disease: Illness or sickness often characterized by typical patient problems (symptoms) and physical findings (signs). Disruption sequence: The events that occur when a fetus that is developing normally is subjected to a destructive agent such as the rubella (German measles) virus.

Essential: 1. Something that cannot be done without.
2. Required in the diet, because the body cannot make it. As in an essential amino acid or an essential fatty acid.
3. Idiopathic. As in essential hypertension. "Essential" is a hallowed term meaning "We don't know the cause."

Fever : Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.).
See the entire definition of Fever

Health: As officially defined by the World Health Organization, a state of complete physical, mental, and social well-being, not merely the absence of disease or infirmity.

Heart: The muscle that pumps blood received from veins into arteries throughout the body. It is positioned in the chest behind the sternum (breastbone; in front of the trachea, esophagus, and aorta; and above the diaphragm muscle that separates the chest and abdominal cavities. The normal heart is about the size of a closed fist, and weighs about 10.5 ounces. It is cone-shaped, with the point of the cone pointing down to the left. Two-thirds of the heart lies in the left side of the chest with the balance in the right chest.
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Heart disease: Any disorder that affects the heart. Sometimes the term "heart disease" is used narrowly and incorrectly as a synonym for coronary artery disease. Heart disease is synonymous with cardiac disease but not with cardiovascular disease which is any disease of the heart or blood vessels. Among the many types of heart disease, see, for example: Angina; Arrhythmia; Congenital heart disease; Coronary artery disease (CAD); Dilated cardiomyopathy; Heart attack (myocardial infarction); Heart failure; Hypertrophic cardiomyopathy; Mitral regurgitation; Mitral valve prolapse; and Pulmonary stenosis.

Heart muscle: A type of muscle with unique features only found in the heart. The heart muscle, or cardiac muscle, is medically called the myocardium ("myo-" being the prefix denoting muscle).

Heart valves: There are four heart valves. All are one-way valves. Blood entering the heart first passes through the tricuspid valve and then the pulmonary valve. After returning from the lungs, the blood passes through the mitral (bicuspid) valve and exits via the aortic valve.

Inferior: In anatomy, below or toward the feet. As opposed to superior. The liver is inferior to the lungs.
See the entire definition of Inferior

Inferior vena cava: A large vein that receives blood from the lower extremities, pelvis and abdomen and delivers it to the right atrium of the heart.

Injury: Harm or hurt. The term "injury" may be applied in medicine to damage inflicted upon oneself as in a hamstring injury or by an external agent on as in a cold injury. The injury may be accidental or deliberate, as with a needlestick injury. The term "injury" may be synonymous (depending on the context) with a wound or with trauma.

Left atrium: The upper right chamber of the heart. The left atrium receives oxygenated blood from the lungs and pumps it down into the left ventricle which delivers it to the body.

Left ventricle: The left lower chamber of the heart that receives blood from the left atrium and pumps it out under high pressure through the aorta to the body.

Lungs: The lungs are a pair of breathing organs located with the chest which remove carbon dioxide from and bring oxygen to the blood. There is a right and left lung.

Metabolism: The whole range of biochemical processes that occur within us (or any living organism). Metabolism consists both of anabolism and catabolism (the buildup and breakdown of substances, respectively). The term is commonly used to refer specifically to the breakdown of food and its transformation into energy.

Mitral valve: A valve in the heart situated between the left atrium and the left ventricle that permits blood to flow from the left atrium into the left ventricle but not in the reverse direction.
See the entire definition of Mitral valve

Muscle: Muscle is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart muscle is called "cardiac muscle." Muscle that is in the walls of arteries and bowel is called "smooth muscle."

Muscular: Having to do with the muscles. Also, endowed with above average muscle development. Muscular system refers to all of the muscles of the body collectively.

Node: Literally a knot, a node is a collection of tissue. For example a lymph node, is a collection of lymphoid tissue. A nodule is a small node, a little collection of tissue.
See the entire definition of Node

Organ: A relatively independent part of the body that carries out one or more special functions. The organs of the human body include the eye, ear, heart, lungs, and liver.

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Oxygen: A colorless, odorless and tasteless gas that makes up about 20% of the air we breathe (and at least half the weight of the entire solid crust of the earth) and which combines with most of the other elements to form oxides. Oxygen is essential to human, animal and plant life.
See the entire definition of Oxygen

Pacemaker: A system that sends electrical impulses to the heart in order to set the heart rhythm. The pacemaker can be the normal "natural" pacemaker of the heart or it can be an electronic device.
See the entire definition of Pacemaker

Posterior: The back or behind, as opposed to the anterior.
See the entire definition of Posterior

Pulmonary: Having to do with the lungs. (The word comes from the Latin pulmo for lung).

Pulmonary artery: One of the two vessels which are formed as terminal branches of the pulmonary trunk and convey unaerated blood to the lungs. The two pulmonary arteries differ in length and anatomy.
See the entire definition of Pulmonary artery

Pulmonary valve: One of the four valves in the heart, the pulmonary valve stands at the opening from the right ventricle in the pulmonary artery trunk. It lets blood head in the right direction (toward the lungs) and keeps it from sloshing back from the pulmonary artery into the heart.

Pulmonary vein: One of four vessels that carry aerated blood from the lungs to the left atrium of the heart. (The four are the right and left superior and inferior pulmonary veins). The pulmonary veins are the only veins that carry bright red oxygenated blood.

Rest: 1. Repose. Relaxation.
2. A fragment of embryonic tissue that has been retained after the period of embryonic development. Also called an embryonic rest.

Rib: One of the 12 paired arches of bone which form the skeletal structure of the chest wall (the rib cage). The ribs attach to the building blocks of the spine (vertebrae) in the back. The 12 pairs of ribs consist of:

  • True ribs: The first seven ribs attach to the sternum (the breast bone) in the front and are known as true ribs (or sternal ribs).
  • False ribs: The lower five ribs do not directly connect to the sternum and are known as false ribs.

See the entire definition of Rib

Rib cage: The structure formed by the thoracic vertebrae and ribs, the sternum (breastbone), and the costal cartilages (that attach the ribs to the sternum).
See the entire definition of Rib cage

Right atrium: The right upper chamber of the heart. The right atrium receives deoxygenated blood from the body through the vena cava and pumps it into the right ventricle which then sends it to the lungs to be oxygenated.

Right ventricle: The lower right chamber of the heart that receives deoxygenated blood from the right atrium and pumps it under low pressure into the lungs via the pulmonary artery.
See the entire definition of Right ventricle

SA node: The SA node (SA stands for sinoatrial) is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood.
See the entire definition of SA node

Septum: A word borrowed from the Latin "saeptum" meaning a "dividing wall or enclosure."
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Sinoatrial node: The sinoatrial node (the SA node) is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood.
See the entire definition of Sinoatrial node back to top

Sternum: Anatomic name for the breast bone, the long flat bone in the upper middle of the front of the chest.
See the entire definition of Sternum

Superior: In antomy, above or over top of. As opposed to inferior. The heart is superior to the stomach. The superior surface of the tongue rests against the palate.
See the entire definition of Superior

Superior vena cava: A large vein that receives blood from the head, neck, upper extremities, and thorax and delivers it to the right atrium of the heart.


See the entire definition of Superior vena cava

Tissue: A tissue in medicine is not like a piece of tissue paper. It is a broad term that is applied to any group of cells that perform specific functions. A tissue in medicine need not form a layer. Thus,

  • The bone marrow is a tissue;
  • Connective tissue consists of cells that make up fibers in the framework supporting other body tissues; and
  • Lymphoid tissue is the part of the body's immune system that helps protect it from bacteria and other foreign entities.

Tricuspid: Having three flaps or cusps. The valve that is called the tricuspid valve is situated between the right atrium and right ventricle and permits blood to flow only from the atrium into the ventricle. The aortic valve in the heart also has three cusps.
See the entire definition of Tricuspid

Tricuspid valve:One of the four heart valves, the tricuspid valve is the first one that blood encounters as it enters the heart. The tricuspid valve stands between the right atrium and right ventricle and allows blood to flow only from the atrium into the ventricle.

Tubes: The "tubes" are medically known as the Fallopian tubes. There are two Fallopian tubes, one on each side, which transport the egg from the ovary to the uterus (the womb). The Fallopian tubes have small hair-like projections called cilia on the cells of the lining.
See the entire definition of Tubes

Vein: A blood vessel that carries blood low in oxygen content from the body back to the heart. The deoxygenated form of hemoglobin (deoxyhemoglobin) in venous blood makes it appear dark. Veins are part of the afferent wing of the circulatory system which returns blood to the heart.
See the entire definition of Vein

Vena cava: The superior vena cava is the large vein which returns blood to the heart from the head, neck and both upper limbs. The inferior vena cava returns blood to the heart from the lower part of the body.
See the entire definition of Vena cava

Ventricle: A chamber of an organ. For example, the four connected cavities (hollow spaces) in the central portion of the brain and the lower two chambers of the heart are called ventricles.

Ventricles: 1, The right ventricle and the left ventricle, the lower two chambers of the heart. 2. Two or more of the four connected spaces within the central portion of the brain.

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 Heart: How the Heart Works Main Article |  Glossary |  Heart: How the Heart Works Index 




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