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    Related Topics

    From Cardiovascular System

    Heart
    Muscular organ responsible for pumping blood throughout the body.
    Subclavian Veins
    Carry blood from the upper limbs to the heart.
    Great Saphenous Vein
    Longest vein in the body, running along the leg.
    Thoracic Aorta
    Part of descending aorta within the chest.
    Radial Arteries
    Supply the lateral aspect of the forearm and hand.
    Basilic Veins
    Superficial veins of the medial upper limb.
    Marginal Branch
    Supplies right ventricle along the margin.
    External Carotid Artery
    Supplies blood to the face and scalp.
    Ulnar Arteries
    Supply the medial aspect of the forearm and hand.
    Dorsal Venous Arch
    Superficial venous network on the dorsum of the foot.
    Femoral Veins
    Major deep veins of the thigh.
    Pulmonary Trunk
    Carries deoxygenated blood from right ventricle to lungs.
    Subclavian Arteries
    Supply blood to the arms and part of the brain.
    Brachial Arteries
    Major artery of the upper arm.
    Posterior Tibial Arteries
    Supply posterior compartment of the leg.
    Ascending Aorta
    Initial portion of the aorta emerging from the heart.
    Right Pulmonary Artery
    Carries blood to right lung.
    Middle Cardiac Vein
    Drains the posterior heart.
    Anterior Tibial Arteries
    Supply anterior compartment of the leg.
    Circumflex Branch
    Curves around to the posterior heart.
    Small Saphenous Vein
    Superficial vein of the posterior leg.
    Left Atrium
    Receives oxygenated blood from the lungs.
    Crista Terminalis
    Smooth muscular ridge in the right atrium.
    External Iliac Arteries
    Continue into the legs as femoral arteries.
    Right Superior Pulmonary Vein
    Returns oxygenated blood from right lung.

    Superior Vena Cava

    Reviewed by our medical team

    Returns deoxygenated blood from upper body.

    Overview

    The superior vena cava (SVC) is a large, valveless vein that returns deoxygenated blood from the upper half of the body to the right atrium of the heart. It is a major component of the systemic venous circulation and plays a vital role in maintaining central venous return. Formed by the union of the left and right brachiocephalic veins, the SVC is essential for draining the head, neck, upper limbs, and upper thorax.

    Location

    The superior vena cava is located in the superior and middle mediastinum. Key anatomical relationships include:

    • Posterior to the right first and second intercostal spaces

    • Anterior and lateral to the trachea

    • Medial to the right lung and pleura

    • Right of the ascending aorta and the pulmonary trunk

    It extends from the junction of the brachiocephalic veins (at the level of the right first costal cartilage) and descends vertically to terminate in the upper portion of the right atrium (at the level of the third costal cartilage).

    Structure

    The superior vena cava is a short (approximately 7 cm), wide-diameter vessel with a thin wall. Key structural features include:

    • Length: 6–8 cm

    • Diameter: 2–2.5 cm in adults

    • Wall composition: Tunica intima (endothelium), thin tunica media (smooth muscle), and adventitia (connective tissue)

    • Tributaries:

      • Right and left brachiocephalic veins (main contributors)

      • Azygos vein (joins posteriorly before entering the right atrium)

    The SVC is a valveless vessel, which allows continuous low-resistance blood flow into the right atrium.

    Function

    The primary function of the superior vena cava is to:

    • Return deoxygenated blood from the upper body — including the head, neck, upper limbs, and chest wall — to the right atrium

    This blood is then pumped into the right ventricle and subsequently to the lungs for oxygenation.

    Physiological Role(s)

    The superior vena cava is crucial for:

    • Maintaining venous return from the upper body: Ensures balanced systemic circulation and cardiac preload

    • Central venous pressure (CVP) monitoring: Pressure within the SVC reflects right atrial pressure and is commonly measured via central venous catheterization

    • Conduit for medical interventions: Catheters, pacemaker leads, and central lines are frequently inserted via tributary veins (e.g., subclavian or internal jugular) into the SVC

    Clinical Significance

    The superior vena cava is clinically significant in multiple scenarios:

    • Superior Vena Cava Syndrome (SVCS): Compression or obstruction of the SVC leads to impaired venous drainage, resulting in facial swelling, venous distention, cyanosis, and dyspnea. Common causes include mediastinal tumors (e.g., lung cancer, lymphoma), thrombosis from central lines, or fibrosis.

    • Central Venous Access: The SVC is the preferred target for central venous catheter placement via the internal jugular or subclavian veins, especially in critical care and chemotherapy administration.

    • Pacemaker and Defibrillator Lead Placement: Leads traverse through the SVC to reach the right atrium or ventricle.

    • Thrombosis and Embolism: Indwelling catheters can predispose to SVC thrombosis, which may propagate and lead to pulmonary embolism.

    • SVC Aneurysm or Malformations: Rare congenital or acquired dilations may result in turbulent flow or thrombus formation.

    • Surgical Considerations: Injury to the SVC during thoracic procedures can lead to massive hemorrhage due to its high flow and thin walls.

    Imaging studies such as CT angiography, MRI, venography, and echocardiography are critical for evaluating SVC patency, compression, and thrombosis. Recognition and treatment of SVC-related conditions are crucial for maintaining effective venous return and preventing cardiopulmonary complications.

    Did you know? The human heart pumps about 70 milliliters of blood with each beat.