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Anatomy of the Heart

Structure and Function of the Heart

  • Heart Chambers: Consists of four chambers: right atrium, right ventricle, left atrium, left ventricle.

    • Right atrium receives deoxygenated blood from the body via the superior and inferior vena cava.

    • Right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery for gas exchange.

    • Left atrium receives oxygenated blood from the lungs via the pulmonary veins.

    • Left ventricle pumps oxygenated blood to the body through the aorta.

Coronary Arteries

  • Right Coronary Artery (RCA): Supplies blood to the heart muscle, originating from the base of the aorta.

  • Left Coronary Artery (LCA): Divided into:

    • Anterior Interventricular Artery: Supplies the anterior wall of the left ventricle.

    • Circumflex Branch: Supplies the lateral wall of the left ventricle.

  • Coronary arteries provide oxygenated blood specifically to the cardiac tissue.

Heart Valves

  • Aortic Valve: Located between the left ventricle and aorta, opens to allow blood flow into the aorta.

  • Pulmonary Valve: Located between the right ventricle and pulmonary artery, regulates blood flow to the lungs.

  • Bicuspid Valve (Mitral Valve): Located between the left atrium and left ventricle, allows blood to flow from atrium to ventricle.

  • Tricuspid Valve: Located between the right atrium and right ventricle, prevents backflow into the atrium.

Blood Flow Dynamics

  • Deoxygenated Blood Return: Blood returns to the heart through the superior and inferior vena cavae into the right atrium.

  • Blood Flow Pathway:

    1. Right atrium contracts, pushing blood through the tricuspid valve into the right ventricle.

    2. Right ventricle contracts, sending blood through the pulmonary valve into the pulmonary arteries leading to the lungs.

    3. Oxygenated blood returns via the pulmonary veins to the left atrium.

    4. Left atrium contracts, allowing blood to flow through the bicuspid valve into the left ventricle.

    5. Left ventricle contracts, sending blood into the aorta for distribution to the body.

Cardiac Cycle

  • Phases of the cardiac cycle:

    • Atrial Systole: Contraction of atria fills ventricles, increasing pressure and opening atrioventricular valves.

    • Ventricular Systole: Contraction of ventricles elevates pressure, closing atrioventricular valves and opening aortic and pulmonary valves, ejecting blood.

    • Diastole: Relaxation phase where the heart chambers refill with blood.

Electrical Activity of the Heart

  • Myogenic Nature: Cardiac muscle is myogenic, meaning it generates its own electrical impulses for contraction.

  • Pacemaker Mechanism:

    1. Sinoatrial Node (SAN) initiates heartbeat and spreads excitation across atria (atria contract).

    2. Atrioventricular Node (AVN) receives and relays signal to the ventricles, leading to contraction from the apex upwards.

  • Electrocardiogram (ECG): A tool for measuring electrical activity; detects arrhythmias and other heart abnormalities.

Blood Pressure and Flow

  • Arterial Pressure: Highest in aorta and arteries, falls progressively in arterioles and capillaries due to resistance.

  • Capillary Exchange: Thin-walled capillaries allow for exchange of oxygen, carbon dioxide, nutrients, and wastes. Hydrostatic pressure drives formation of tissue fluid.

  • Lymphatic System: Excess tissue fluid is drained into lymphatic vessels, eventually returned to blood circulation through the thoracic duct.

Summary

  • The heart functions as a dual pump maintaining circulation, utilizing a structured network of chambers, valves, and a comprehensive electrical control system. The cardiac cycle, influenced by pressure variations, is vital for efficient blood circulation through the lungs and body tissues. Understanding the heart's anatomy, blood flow, and electrical conduction is crucial for identifying cardiovascular diseases and their management.