Glossary for the Heart

Heart Anatomy & Function

• Atria: The two upper chambers of the heart that receive blood (right atrium receives deoxygenated blood, left atrium receives oxygenated blood).
• Ventricles: The two lower chambers of the heart that pump blood (right ventricle to the lungs, left ventricle to the body).
• Atrioventricular (AV) Valves: The heart valves that separate the atria from the ventricles (tricuspid valve on the right, bicuspid/mitral valve on the left).
• Bicuspid (Mitral) Valve: The left AV valve, allowing blood flow from the left atrium to the left ventricle while preventing backflow.
• Tricuspid Valve: The right AV valve, preventing backflow from the right ventricle to the right atrium.
• Semilunar Valves: Valves located at the exits of the ventricles (pulmonary and aortic valves) that prevent blood backflow.
• Pulmonary Valve: The valve between the right ventricle and the pulmonary artery, preventing backflow into the right ventricle.
• Coronary Arteries: Arteries that supply oxygenated blood to the heart muscle itself.
• Endocardium: The thin inner layer of the heart lining the chambers and valves.
• Myocardium: The thick muscular layer of the heart responsible for contraction.
• Pericardium: The protective double-layered membrane surrounding the heart.

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Heart Electrical System

• Sinoatrial (SA) Node: The heart’s natural pacemaker located in the right atrium, initiating electrical impulses for heartbeat.
• Atrioventricular (AV) Node: A secondary pacemaker that slows electrical conductionThe transmission of nerve impulses along neurons. between the atria and ventricles, ensuring proper contraction timing.
• AV Bundle (Bundle of His): A pathway for electrical signals between the AV node and ventricles.
• AV Branches: The right and left branches of the AV bundle, directing signals to each ventricle.
• Purkinje Fibers: Fibers that rapidly distribute electrical impulses throughout the ventricles, causing contraction.
• Autorhythmic Cells: Specialized cardiac muscle cellsThe basic structural and functional units of life. that generate and conduct electrical impulses without external stimulation.
• Gap Junctions: Protein channelsProtein passages in the cell membrane that allow specific molecules to pass through. in cardiac muscle cells allowing ionsCharged atoms or molecules. and electrical impulses to pass between cells.
• Desmosomes: Structures within intercalated discs Structures in cardiac muscle that allow electrical connectivity. that connect cardiac muscle cells and prevent separation during contraction.
• Intercalated Discs: Specialized connections between cardiac muscle cells, facilitating coordinated contraction.
• Junctional Rhythm: A heart rhythm originating from the AV node due to SA node failure.

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Cardiac Cycle & Blood Flow

• Atrial Contraction: The contraction of the atria, pushing blood into the ventricles.
• Ventricular Filling: The phase when the ventricles fill with blood from the atria.
• Ventricular Ejection: The phase when the ventricles contract, pushing blood into the aorta and pulmonary artery.
• Diastole: The relaxation phase of the heart when chambers fill with blood.
• Isovolumetric Contraction: The phase when the ventricles contract but no blood is ejected because all valves are closed.
• Isovolumetric Relaxation: The phase after ventricular contraction when pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. drops but no blood enters because valves remain closed.
• Preload: The amount of stretch in the ventricles before contraction, determined by the volume of blood filling the heart.
• Afterload: The resistanceThe opposition to airflow in the respiratory tract, influenced by airway diameter. the ventricles must overcome to eject blood (higher resistance means harder work for the heart).
• Contractility: The strength of ventricular contraction, independent of preload.

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Cardiac Output & Hemodynamics

• Cardiac Output (CO): The amount of blood pumped by the heart per minute, calculated as:
  CO=Heart Rate×Stroke VolumeCO = \text{Heart Rate} \times \text{Stroke Volume}CO=Heart Rate×Stroke Volume
• Stroke Volume (SV): The amount of blood ejected by a ventricle per beat.
• Ejection Fraction: The percentage of blood ejected from a ventricle per beat, indicating heart efficiency.
• End-Diastolic Volume (EDV): The volume of blood in a ventricle at the end of diastole (before contraction).
• End-Systolic Volume (ESV): The volume of blood left in a ventricle after contraction.

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Heart Sounds & Blood Pressure

• Pulse Pressure: The difference between systolic and diastolic blood pressure, indicating the force of each heartbeat.
• Hypertension: High blood pressure, increasing the heart’s workload.

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Heart Defects & Conditions

• Ventricular Septal Defect (VSD): A hole in the septum separating the ventricles, causing abnormal blood flow.
• Foramen Ovale: A fetal heart opening between the atria, allowing blood to bypass the lungs before birth.
• Fossa Ovalis: The remnant of the foramen ovale in the adult heart.
• Ductus Arteriosum: A fetal blood vessel connecting the pulmonary artery to the aorta, bypassing the lungs.
• Ligamentum Arteriosum: The remnant of the ductus arteriosum after birth.

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Cardiac Electrical Activity (ECG Waves)

• P Wave: Represents atrial depolarizationThe loss of electrical charge across a membrane, triggering an action potential. (atrial contraction).
• QRS Wave (Complex): Represents ventricular depolarization (ventricular contraction).
• Plateau Phase: A period in cardiac muscle contraction when calcium influx balances potassium(K⁺): Major ICF cation; essential for muscle and nerve function. efflux, prolonging depolarization.
• Sinus Rhythm: The normal heart rhythm initiated by the SA node.

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Heart Rate Conditions

• Bradycardia: Abnormally slow heart rate (<60 bpm).
• Tachycardia: Abnormally fast heart rate (>100 bpm).

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Circulatory Disorders & Congestion

• Peripheral Congestion: Blood pooling in the systemic circuitThe part of the circulatory system that carries oxygenated blood from the heart to the body and retu due to right heart failure, causing swelling in limbs.
• Pulmonary Congestion: Fluid accumulation in the lungs due to left heart failure, leading to breathing difficulties.
• Edema: Swelling caused by excess fluid in tissues, often due to poor circulation.