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    Related Topics

    From Cardiovascular System

    Right Pulmonary Artery
    Carries blood to right lung.
    Chordae Tendineae
    Tendon-like cords attaching valve leaflets to papillary muscles.
    Brachiocephalic Veins
    Formed by the union of subclavian and internal jugular veins.
    Dorsal Venous Arch
    Superficial venous network on the dorsum of the foot.
    External Iliac Arteries
    Continue into the legs as femoral arteries.
    Internal Iliac Veins
    Drain pelvic organs.
    Right Superior Pulmonary Vein
    Returns oxygenated blood from right lung.
    External Iliac Veins
    Drain lower limbs and join internal iliac veins.
    Common Iliac Arteries
    Branch from abdominal aorta to supply the lower limbs.
    Internal Jugular Veins
    Drain blood from the brain and deep structures of the head.
    Left Pulmonary Artery
    Carries blood to left lung.
    Fibrous Pericardium
    Outer layer of the pericardium made of dense connective tissue.
    Internal Carotid Artery
    Supplies blood to the brain.
    Moderator Band
    Muscular band of heart tissue found in the right ventricle.
    Left Common Carotid Artery
    Supplies the head and neck.
    Popliteal Arteries
    Continuation of femoral arteries behind the knee.
    Circumflex Branch
    Curves around to the posterior heart.
    Right Ventricle
    Pumps blood to the lungs via pulmonary artery.
    Right Atrium
    Receives deoxygenated blood from the body.
    Superior Vena Cava
    Returns deoxygenated blood from upper body.
    Thoracic Aorta
    Part of descending aorta within the chest.
    Median Cubital Vein
    Connects cephalic and basilic veins at the elbow.
    Small Cardiac Vein
    Drains right atrium and ventricle.
    Coronary Sinus
    Collects blood from coronary veins.
    Pulmonary Valve
    Valve between right ventricle and pulmonary trunk.

    Visceral Layer (Epicardium)

    Reviewed by our medical team

    Covers the external surface of the heart.

    Overview

    The visceral layer of the serous pericardium, also known as the epicardium, is the innermost layer of the pericardium and forms the outermost layer of the heart wall. It plays a protective role, produces pericardial fluid, and contributes structurally to the coronary vasculature and fat deposition. As part of both the pericardial sac and the heart wall itself, the epicardium is essential for cardiac function, lubrication, and immune defense.

    Location

    The epicardium is located:

    • Directly on the outer surface of the heart, covering the myocardium

    • Continuous with the parietal layer of the serous pericardium at the root of the great vessels (where the serous layer reflects back)

    • In direct contact with the pericardial cavity, which contains serous fluid for frictionless cardiac motion

    It envelops all four chambers of the heart and extends over the roots of the great arteries and veins before reflecting to form the parietal layer.

    Structure

    The epicardium is a thin, transparent layer composed of:

    • Mesothelium: A single layer of flattened epithelial cells that secretes serous fluid

    • Submesothelial connective tissue: Contains fibroblasts, fat, nerves, lymphatics, and the coronary blood vessels

    • Fat deposits: Especially over the atrioventricular and interventricular grooves, where major coronary arteries and veins lie

    Unlike the fibrous pericardium, the epicardium is delicate and smooth, enabling it to move freely with each heartbeat.

    Function

    The visceral pericardium (epicardium) serves several essential functions:

    • Protection: Shields the myocardium and coronary vessels from mechanical injury and external irritation

    • Secretion: Produces pericardial fluid in conjunction with the parietal layer, reducing friction during cardiac movement

    • Structural support: Provides a matrix for coronary vessels and nerves to travel through

    • Immunological activity: Houses immune cells capable of responding to cardiac injury or infection

    Physiological Role(s)

    The epicardium plays multiple dynamic roles in cardiovascular physiology:

    • Lubrication: Serous fluid secreted by mesothelial cells allows for smooth, frictionless movement of the heart within the pericardial sac

    • Vascular development: During embryogenesis, the epicardium contributes to the formation of coronary vessels and fibroblasts

    • Fat storage and energy support: Adipose tissue within the epicardium may support energy demands of the myocardium and insulate coronary arteries

    • Endocrine signaling: Epicardial fat produces cytokines and adipokines that influence local inflammation and myocardial metabolism

    Clinical Significance

    The visceral layer of the pericardium (epicardium) is involved in various physiological and pathological processes:

    • Epicarditis: Inflammation of the epicardium, often accompanying myocarditis or pericarditis, resulting in chest pain, pericardial effusion, or arrhythmias

    • Pericardial Effusion: When inflamed, the epicardium may overproduce fluid, leading to accumulation in the pericardial space, which can compress the heart (tamponade)

    • Coronary Artery Disease: The epicardium houses the coronary arteries; atherosclerotic changes can occur within these vessels, leading to myocardial ischemia

    • Epicardial Fat Dysfunction: Excess epicardial adipose tissue is associated with obesity, metabolic syndrome, atrial fibrillation, and coronary artery disease due to pro-inflammatory cytokine release

    • Surgical Access: During cardiac surgery (e.g., coronary artery bypass grafting), the epicardium is incised to access the coronary vessels or implant devices

    • Imaging: Epicardial thickness and fat distribution can be evaluated using echocardiography, cardiac MRI, and CT scans for cardiovascular risk assessment

    Understanding the structure and function of the epicardium is crucial for interpreting pericardial diseases, guiding cardiac surgery, and managing metabolic contributions to cardiovascular pathology.

    Did you know? Oxygenated blood is carried to the heart via the pulmonary veins.