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Anatomy & Physiology: The Cardiovascular System - The Heart

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Terms in this set (22)

  • Pulmonary and Systemic Circuits

    The heart has two side-by-side pumps: the right side pumps oxygen-poor blood to the lungs via the pulmonary circuit, and the left side pumps oxygenated blood to body tissues via the systemic circuit.

  • Location and Size of the Heart

    The heart is roughly fist-sized, located in the mediastinum between the second rib and fifth intercostal space, with about two-thirds left of the midsternal line.

  • Pericardium Layers

    The pericardium is a double-walled sac with a superficial fibrous layer and a deep serous layer (parietal and visceral layers) separated by a fluid-filled cavity to reduce friction.

  • Heart Wall Layers

    Three layers: epicardium (visceral serous pericardium), myocardium (cardiac muscle with fibrous skeleton), and endocardium (endothelial lining of chambers and valves).

  • Heart Chambers and Great Vessels

    Four chambers: two atria (receiving chambers) and two ventricles (pumping chambers). Great vessels include the aorta, pulmonary trunk, venae cavae, and pulmonary veins.

  • Atrioventricular (AV) Valves

    Prevent backflow into atria during ventricular contraction. Right AV valve is tricuspid (3 cusps), left AV valve is mitral/bicuspid (2 cusps). Chordae tendineae anchor valve cusps to papillary muscles.

  • Semilunar (SL) Valves

    Prevent backflow from arteries into ventricles during relaxation. Pulmonary valve between right ventricle and pulmonary trunk; aortic valve between left ventricle and aorta. Each has three crescent-shaped cusps.

  • Differences Between Right and Left Ventricles

    Right ventricle pumps to low-pressure pulmonary circuit; left ventricle pumps to high-pressure systemic circuit and has walls 3 times thicker.

  • Coronary Circulation

    Supplies blood to heart muscle itself via coronary arteries from the aorta; cardiac veins drain into coronary sinus and then right atrium.

  • Cardiac Muscle Microscopic Anatomy

    Cardiac myocytes are short, branched, interconnected by intercalated discs containing desmosomes and gap junctions, allowing the heart to function as a syncytium.

  • Differences Between Skeletal and Cardiac Muscle

    Cardiac muscle has autorhythmic pacemaker cells, contracts as a unit, has longer refractory periods preventing tetanus, and relies mainly on aerobic respiration.

  • Intrinsic Cardiac Conduction System

    Network of autorhythmic cells including SA node, AV node, AV bundle, bundle branches, and Purkinje fibers that coordinate heartbeat.

  • Sequence of Cardiac Excitation

    Impulse starts at SA node → AV node → AV bundle → bundle branches → Purkinje fibers, completing ventricular depolarization in ~0.22 seconds.

  • Heart Rate Regulation by Autonomic Nervous System

    Sympathetic stimulation increases heart rate and contractility; parasympathetic stimulation decreases heart rate via vagus nerve.

  • Action Potential in Contractile Cardiac Muscle Cells

    Rapid depolarization by Na+ influx, plateau phase due to Ca2+ influx, and repolarization by K+ efflux; long action potential prevents tetanus.

  • Electrocardiogram (ECG) Components

    P wave: atrial depolarization; QRS complex: ventricular depolarization; T wave: ventricular repolarization.

  • Phases of the Cardiac Cycle

    Includes ventricular filling, isovolumic contraction, ventricular ejection, and isovolumic relaxation, coordinated with valve opening and closing.

  • Heart Sounds

    First sound (lub) is AV valves closing at ventricular systole start; second sound (dup) is SL valves closing at ventricular diastole start.

  • Cardiac Output (CO)

    CO = Heart Rate (HR) × Stroke Volume (SV); average adult CO is about 5.25 L/min at rest.

  • Factors Affecting Stroke Volume

    Preload (degree of muscle stretch), contractility (strength of contraction), and afterload (arterial pressure opposing ejection).

  • Regulation of Heart Rate

    Influenced by autonomic nervous system, hormones (epinephrine, thyroxine), ions, age, sex, exercise, and body temperature.

  • Common Cardiac Disorders

    Includes arrhythmias, fibrillation, heart block, congestive heart failure, and congenital defects like patent foramen ovale and tetralogy of Fallot.