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The Heart
Chapter 14 definitions
| Term | Definition |
|---|---|
| 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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