6.8: Glossary

Key Terms and Definitions 

• Anastomosis: (plural = anastomoses) area where vessels unite to allow blood to circulate even if there may be partial blockage in another branch.
• Anterior cardiac veins: vessels that parallel the small cardiac arteries and drain the anterior surface of the right ventricle; bypass the coronary sinus and drain directly into the right atrium.
• Anterior interventricular artery: (also, left anterior descending artery or LAD) major branch of the left coronary artery that follows the anterior interventricular sulcus.
• Anterior interventricular sulcus: sulcus located between the left and right ventricles on the anterior surface of the heart.
• Aortic valve: (also, aortic semilunar valve) valve located at the base of the aorta.
• Artificial pacemaker: medical device that transmits electrical signals to the heart to ensure that it contracts and pumps blood to the body.
• Atrioventricular (AV) node: cluster of myocardial cells located in the inferior portion of the right atrium within the atrioventricular septum; receives the impulse from the SA node, pauses, and then transmits it into specialized conducting cells within the interventricular septum.
• Atrioventricular bundle: (also, bundle of His) group of specialized myocardial conductile cells that transmit the impulse from the AV node through the interventricular septum; form the left and right atrioventricular bundle branches.
• Atrioventricular bundle branches: (also, left or right bundle branches) specialized myocardial conductile cells that arise from the bifurcation of the atrioventricular bundle and pass through the interventricular septum; lead to the Purkinje fibers and also to the right papillary muscle via the moderator band.
• Atrioventricular septum: cardiac septum located between the atria and ventricles; atrioventricular valves are located here.
• Atrioventricular valves: one-way valves located between the atria and ventricles; the valve on the right is called the tricuspid valve, and the one on the left is the mitral or bicuspid valve.
• Atrium: (plural = atria) upper or receiving chamber of the heart that pumps blood into the lower chambers just prior to their contraction; the right atrium receives blood from the systemic circuit that flows into the right ventricle; the left atrium receives blood from the pulmonary circuit that flows into the left ventricle.
• Auricle: extension of an atrium visible on the superior surface of the heart.
• Bundle of His: (also, atrioventricular bundle) group of specialized myocardial conductile cells that transmit the impulse from the AV node through the interventricular septum; form the left and right atrioventricular bundle branches.
• Cardiac cycle: period of time between the onset of atrial contraction (atrial systole) and ventricular relaxation (ventricular diastole).
• Cardiac notch: depression in the medial surface of the superior lobe of the left lung where the apex of the heart is located.
• Cardiac skeleton: (also, skeleton of the heart) reinforced connective tissue located within the atrioventricular septum; includes four rings that surround the openings between the atria and ventricles, and the openings to the pulmonary trunk and aorta; the point of attachment for the heart valves.
• Cardiomyocyte: muscle cell of the heart.
• Chordae tendineae: string-like extensions of tough connective tissue that extend from the flaps of the atrioventricular valves to the papillary muscles.
• Circumflex artery: branch of the left coronary artery that follows coronary sulcus.
• Coronary arteries: branches of the ascending aorta that supply blood to the heart; the left coronary artery feeds the left side of the heart, the left atrium and ventricle, and the interventricular septum; the right coronary artery feeds the right atrium, portions of both ventricles, and the heart conduction system.
• Coronary sinus: large, thin-walled vein on the posterior surface of the heart that lies within the atrioventricular sulcus and drains the heart myocardium directly into the right atrium.
• Coronary sulcus: sulcus that marks the boundary between the atria and ventricles.
• Coronary veins: vessels that drain the heart and generally parallel the large surface arteries.
• Electrocardiogram (ECG): surface recording of the electrical activity of the heart that can be used for diagnosis of irregular heart function; also abbreviated as EKG.
• Endocardium: innermost layer of the heart lining the heart chambers and heart valves; composed of endothelium reinforced with a thin layer of connective tissue that binds to the myocardium.
• Epicardium: innermost layer of the serous pericardium and the outermost layer of the heart wall.
• Foramen ovale: opening in the fetal heart that allows blood to flow directly from the right atrium to the left atrium, bypassing the fetal pulmonary circuit.
• Fossa ovalis: oval-shaped depression in the interatrial septum that marks the former location of the foramen ovale.
• Great cardiac vein: vessel that follows the interventricular sulcus on the anterior surface of the heart and flows along the coronary sulcus into the coronary sinus on the posterior surface; parallels the anterior interventricular artery and drains the areas supplied by this vessel.
• Heart rate (HR): number of times the heart contracts (beats) per minute.
• Hypertrophic cardiomyopathy: pathological enlargement of the heart, generally for no known reason.
• Inferior vena cava: large systemic vein that returns blood to the heart from the inferior portion of the body.
• Interatrial septum: cardiac septum located between the two atria; contains the fossa ovalis after birth.
• Intercalated disc: physical junction between adjacent cardiac muscle cells; consisting of desmosomes, specialized linking proteoglycans, and gap junctions that allow passage of ions between the two cells.
• Internodal pathways: specialized conductile cells within the atria that transmit the impulse from the SA node throughout the myocardial cells of the atrium and to the AV node.
• Interventricular septum: cardiac septum located between the two ventricles.
• Left atrioventricular valve: (also, mitral valve or bicuspid valve) valve located between the left atrium and ventricle; consists of two flaps of tissue.
• Marginal arteries: branches of the right coronary artery that supply blood to the superficial portions of the right ventricle.
• Middle cardiac vein: vessel that parallels and drains the areas supplied by the posterior interventricular artery; drains into the great cardiac vein.
• Mitral valve: (also, left atrioventricular valve or bicuspid valve) valve located between the left atrium and ventricle; consists of two flaps of tissue.
• Moderator band: band of myocardium covered by endocardium that arises from the inferior portion of the interventricular septum in the right ventricle and crosses to the anterior papillary muscle; contains conductile fibers that carry electrical signals followed by contraction of the heart.
• Myocardial conducting cells: specialized cells that transmit electrical impulses throughout the heart and trigger contraction by the myocardial contractile cells.
• Myocardial contractile cells: bulk of the cardiac muscle cells in the atria and ventricles that conduct impulses and contract to propel blood.
• Myocardium: thickest layer of the heart composed of cardiac muscle cells built upon a framework of primarily collagenous fibers and blood vessels that supply it and the nervous fibers that help to regulate it.
• P wave: component of the electrocardiogram that represents the depolarization of the atria.
• Pacemaker: cluster of specialized myocardial cells known as the SA node that initiates the sinus rhythm.
• Papillary muscle: extension of the myocardium in the ventricles to which the chordae tendineae attach.
• Pectinate muscles: muscular ridges seen on the anterior surface of the right atrium.
• Pericardial cavity: cavity surrounding the heart filled with a lubricating serous fluid that reduces friction as the heart contracts.
• Pericardial sac: (also, pericardium) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium.
• Pericardium: (also, pericardial sac) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium.
• Posterior cardiac vein: vessel that parallels and drains the areas supplied by the marginal artery branch of the circumflex artery; drains into the great cardiac vein.
• Posterior interventricular artery: (also, posterior descending artery) branch of the right coronary artery that runs along the posterior portion of the interventricular sulcus toward the apex of the heart and gives rise to branches that supply the interventricular septum and portions of both ventricles.
• Posterior interventricular sulcus: sulcus located between the left and right ventricles on the posterior surface of the heart.
• Pulmonary arteries: left and right branches of the pulmonary trunk that carry deoxygenated blood from the heart to each of the lungs.
• Pulmonary capillaries: capillaries surrounding the alveoli of the lungs where gas exchange occurs: carbon dioxide exits the blood and oxygen enters.
• Pulmonary circuit: blood flow to and from the lungs.
• Pulmonary trunk: large arterial vessel that carries blood ejected from the right ventricle; divides into the left and right pulmonary arteries.
• Pulmonary valve: (also, pulmonary semilunar valve, the pulmonic valve, or the right semilunar valve) valve at the base of the pulmonary trunk that prevents backflow of blood into the right ventricle; consists of three flaps.
• Pulmonary veins: veins that carry highly oxygenated blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and to the many branches of the systemic circuit.
• Purkinje fibers: specialized myocardial conduction fibers that arise from the bundle branches and spread the impulse to the myocardial contraction fibers of the ventricles.
• QRS complex: component of the electrocardiogram that represents the depolarization of the ventricles and includes, as a component, the repolarization of the atria.
• Right atrioventricular valve: (also, tricuspid valve) valve located between the right atrium and ventricle; consists of three flaps of tissue.
• Semilunar valves: valves located at the base of the pulmonary trunk and at the base of the aorta.
• Septum: (plural = septa) walls or partitions that divide the heart into chambers.
• Sinoatrial (SA) node: known as the pacemaker, a specialized clump of myocardial conducting cells located in the superior portion of the right atrium that has the highest inherent rate of depolarization that then spreads throughout the heart.
• Sinus rhythm: normal contractile pattern of the heart.
• Small cardiac vein: parallels the right coronary artery and drains blood from the posterior surfaces of the right atrium and ventricle; drains into the coronary sinus, middle cardiac vein, or right atrium.
• Sulcus: (plural = sulci) fat-filled groove visible on the surface of the heart; coronary vessels are also located in these areas.
• Superior vena cava: large systemic vein that returns blood to the heart from the superior portion of the body.
• Systemic circuit: blood flow to and from virtually all of the tissues of the body.
• Systole: period of time when the heart muscle is contracting.
• T wave: component of the electrocardiogram that represents the repolarization of the ventricles.
• Trabeculae carneae: ridges of muscle covered by endocardium located in the ventricles.
• Tricuspid valve: term used most often in clinical settings for the right atrioventricular valve.
• Valve: in the cardiovascular system, a specialized structure located within the heart or vessels that ensures one-way flow of blood.
• Ventricle: one of the primary pumping chambers of the heart located in the lower portion of the heart; the left ventricle is the major pumping chamber on the lower left side of the heart that ejects blood into the systemic circuit via the aorta and receives blood from the left atrium; the right ventricle is the major pumping chamber on the lower right side of the heart that ejects blood into the pulmonary circuit via the pulmonary trunk and receives blood from the right atrium.