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The Heart

Chapter 14 definitions

Mediastinum The space between the lungs and beneath the sternum where the heart resides
Base Broadest part of the heart located in the upper right; where the great vessels enter and leave the heart
Apex The pointed end of the heart located in the lower left; the point of maximum impulse
Pericardium Double-walled sac that surrounds the heart; has 2 layers, fibrous pericardium and serous pericardium
Fibrous pericardium Loose-fitting sac of strong connective tissue; the outer-most layer of the pericardium
Serous pericardium Covers the heart's surface; has 2 layers, the parietal layer and the visceral layer
Parietal layer Layer of the serous pericardium which lines the inside of the fibrous pericardium
Visceral layer Layer of the serous pericardium which covers the heart's surface
Pericardial cavity Cavity between the parietal and visceral layers that contains a small amount of serous fluid, which helps prevent friction as the heart beats
Endocardium Layer of the heart wall consisting of a thin layer of squamous epithelial cells that lines the heart's chambers, covers the valves, and continues into the vessels
Myocardium Forms the midle layer of the heart wall. Composed of cardiac muscle, it's the thickest of the layers and performs the work of the heart
Epicardium Layer of the heart wall that covers the heart's surface; consists of a thin layer of squamous epithelial cells
Atria 2 upper chambers of the heart; recieve blood from the body (right) or the lungs (left)
Ventricles 2 lower chambers of the heart; serve as pumps, receiving blood from the atria and then pumping it to the lungs (right) and the body (left)
Cusps Leaflets; flaps of tissue that form each valve
Atrioventricular valve AV valve; regulates flow between the atria and the ventricles; the heart consists of 2 - the triscuspid and the bicuspid or mitral
Semilunar valve Regulate flow between the ventricles and the great arteries; the heart consists of 2 - the pulmonary and the aortic
Tricuspid valve The right AV valve; consists of 3 leaflets; prevents backflow from the right ventricle to the atria
Mitral valve Bicuspid valve; the left AV valve; consists of 2 leaflets; prevents backflow from the left ventricle to the left atria
Pulmonary valve Semilumar valve that prevents backflow from the pulmonary artery to the right ventricle
Aortic valve Semilunar valve that prevents backflow from the aorta to the left ventricle
Skeleton of the heart Semi-rigid, fibrous, connective tissue that encircles each valve; offers support for the heart; keeps the valves from stretching; acts as an insulating barrier between the atria and the ventricles
Valvular insufficiency Occurs when a heart valve fails to prevent backflow of blood during contraction; allowing the blood to regurgitate
Stenotic valve A valve that has become narroed forcing the heart to work harder
Heart murmur Abnormal heart sound which can be heard through a stethoscope
Chordae tendineae Strands of fibrous connective tissue that extend from conical papillary muscles on the floor of the ventricle to the valve cusps
Coronary arteries Deliver oxygenated blood to the myocardium
Atherosclerosis Coronary arteries become blocked or narrowed by a buildup of cholesterol and fatty deposits
Ischemia Depriving the heart tissue of oxygen
Angina pectoris A partially blocked vessel spasms or the heart demands more oxygen than the narrowed vessel can supply resulting in ischemia and chest pain
Coronary sinus Large transverse vein on the heart's exterior, which returns blood to the right atrium; where most cardiac veins empty
Automaticity The heart contracts spontaneously
Rhythmicity The heart beats regularly
Sinoatrial node SA node; in the wall of the right atrium just below the opening of the superior vena cava where normal cardiac impulses arise; the heart's primary pacemaker
Atrioventricular node AV node; located near the right AV valve at the lower end of the interatrial septum; ectopic pacemaker
Atrioventricular bundle Bundle of His; where impulse picks up speed after passing through the AV node
Purkinje fibers Conduct impulses throughout the muscle of both ventricles, causing them to contract simultaneously; ectopic pacemaker
Arrhythmia Irregular heartbeat
P wave Represents atrial depolarization; occurs right before the atria contract
PR interval Represents the time it takes for the cardiac impulse to travel from the atria to the ventricles
QRS complex Represents ventricular depolarization
ST segment Represents the end of ventricular depolarization and the beginning of repolarization
T wave Represents ventricular repolarization
Atrial flutter Occurs when an ectopic focus in the atria fires rapidly, causing the atria to contract between 200 & 400 times per minute; not usually life-threatening
Ventricular fibrillation Causes the heart to quiver rather than contract; cardiac output plummets and cardiac arrest may quickly follow; life-threatening emergency
Systole Phase of the cardiac cycle in which the heart contracts
Diastole Phase of the cardia cycle in which the heart relaxes
Isovolumetric Something having the same or equal volume
Cardiac output The amount of blood the heart pumps in 1 minute; to determine, multiply heart rate by stroke volume
Heart rate The number of times the heart beats in 1 minute
Stroke volume The amount of blood ejected with each heart beat; 60-80% of the blood volume of the ventricles
Bradycardia A persistant pulse rate slower than 60 bpm; commonly occurs during sleep or in athletes
Tachycardia A persistant resting heart rate greater than 100 bpm
Proprioceptors In the muscles and joints; signal the cardiac center of changes in physical activity
Chemoreceptors Found in the aortic arch, carotid arteries, and medulla; detects increases in CO2, decreases in oxygen, and decreases in pH
Baroreceptors Pressoreceptors; pressure sensors in the aorta and internal carotid arteries; detect changes in blood pressure
Ejection fraction The percentage of blood volume the ventricles eject
Preload The amount of tension, or stretch, in the ventricular muscle just before it contracts
Contractility The force with which ventricular ejection occurs
Afterload The forces the heart must work against to eject its volume of blood
Starling's law of the heart The more the ventricle is stretched (within limits), the more forcefully it will contract
Inotropic agents Factors that affect contractility; positive agents include excess calcium and epinephrine; negative agents include calcium deficiency and potassium excess
Chronotropic agents Factors that influence heart rate; positive agents include epinephrine and low levels of calcium; negative agents include acetylcholine and excess levels of potassium
Congestive heart failure CHF; either ventricle fails to pump blood effectively due to being weakened
Created by: cbooher16



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