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    From Cardiovascular System

    Femoral Veins
    Major deep veins of the thigh.
    Internal Iliac Arteries
    Supply blood to pelvic organs.
    Superior Vena Cava
    Returns deoxygenated blood from upper body.
    External Jugular Veins
    Drain blood from the face and scalp.
    Common Iliac Arteries
    Branch from abdominal aorta to supply the lower limbs.
    Femoral Arteries
    Main arteries supplying the thighs.
    Parietal Layer
    Lines the internal surface of the fibrous pericardium.
    Papillary Muscles
    Muscles that anchor the heart valves via chordae tendineae.
    Marginal Branch
    Supplies right ventricle along the margin.
    External Carotid Artery
    Supplies blood to the face and scalp.
    Thoracic Aorta
    Part of descending aorta within the chest.
    Right Ventricle
    Pumps blood to the lungs via pulmonary artery.
    Serous Pericardium
    Inner layer of the pericardium consisting of parietal and visceral layers.
    External Iliac Veins
    Drain lower limbs and join internal iliac veins.
    Abdominal Aorta
    Part of descending aorta within the abdomen.
    Aortic Valve
    Valve between left ventricle and aorta.
    Internal Jugular Veins
    Drain blood from the brain and deep structures of the head.
    Anterior Cardiac Veins
    Drain directly into the right atrium.
    Radial Arteries
    Supply the lateral aspect of the forearm and hand.
    Fibrous Pericardium
    Outer layer of the pericardium made of dense connective tissue.
    Anterior Interventricular Branch
    Supplies anterior interventricular septum (LAD).
    Subclavian Veins
    Carry blood from the upper limbs to the heart.
    Posterior Tibial Arteries
    Supply posterior compartment of the leg.
    Left Coronary Artery
    Supplies blood to left side of heart.
    External Iliac Arteries
    Continue into the legs as femoral arteries.

    Pulmonary Trunk

    Reviewed by our medical team

    Carries deoxygenated blood from right ventricle to lungs.

    Overview

    The pulmonary trunk is a large arterial vessel that emerges from the right ventricle of the heart and serves as the main conduit for deoxygenated blood being transported to the lungs for oxygenation. It is the first component of the pulmonary circulation and quickly bifurcates into the right and left pulmonary arteries. Unlike most arteries that carry oxygen-rich blood, the pulmonary trunk and its branches carry oxygen-poor blood — a unique feature of the pulmonary vascular system.

    Location

    The pulmonary trunk originates from the right ventricle of the heart and ascends slightly posteriorly and to the left. It lies:

    • Anterior to the ascending aorta at its origin

    • Left of the aorta as it ascends

    • Below the aortic arch before it bifurcates

    At the level of the T5–T6 vertebrae (around the sternal angle), it bifurcates into:

    • Right pulmonary artery – passes horizontally across the midline to the right lung

    • Left pulmonary artery – passes horizontally to the left lung

    Structure

    The pulmonary trunk is a thick-walled, elastic artery designed to accommodate large volumes of blood ejected from the right ventricle during systole. Key structural features include:

    • Origin: Conus arteriosus (infundibulum) of the right ventricle

    • Length: Approximately 5 cm

    • Diameter: Roughly 3 cm in adults

    • Wall layers: Tunica intima (endothelium), tunica media (smooth muscle and elastic fibers), and tunica adventitia (connective tissue)

    • Pulmonary valve: A semilunar valve located at the origin of the trunk, preventing backflow into the right ventricle during diastole

    Function

    The primary function of the pulmonary trunk is to:

    • Transport deoxygenated blood from the right ventricle to the lungs via the pulmonary arteries

    • Serve as the starting point of the pulmonary circulation

    This ensures that blood is directed toward the alveolar capillaries in the lungs, where gas exchange occurs — carbon dioxide is released, and oxygen is absorbed.

    Physiological Role(s)

    The pulmonary trunk plays multiple vital roles in cardiovascular physiology:

    • Manages low-pressure, high-volume flow: Unlike systemic arteries, the pulmonary trunk operates under lower pressure (normally 15–25 mmHg systolic) to protect the delicate pulmonary capillaries.

    • Supports gas exchange: It ensures timely delivery of blood to the lungs for continuous oxygenation and carbon dioxide removal.

    • Coordinates with cardiac cycle: The pulmonary valve and elastic nature of the trunk allow smooth systolic ejection and diastolic closure, minimizing energy loss.

    Clinical Significance

    The pulmonary trunk is involved in various congenital, structural, and hemodynamic disorders:

    • Pulmonary Hypertension: Elevated pressure in the pulmonary trunk and its branches can result from chronic lung disease, left heart disease, or idiopathic causes. Leads to right ventricular strain and eventual failure.

    • Pulmonary Embolism: A life-threatening condition where a thrombus lodges in the pulmonary trunk or its branches, causing acute right heart failure, hypoxia, or death.

    • Truncus Arteriosus: A rare congenital defect where the pulmonary trunk and aorta fail to separate during development, resulting in a single outflow tract — requires early surgical correction.

    • Transposition of the Great Arteries (TGA): A condition in which the pulmonary trunk arises from the left ventricle instead of the right, disrupting normal circulation and requiring neonatal intervention.

    • Dilation or Aneurysm: Pulmonary trunk dilatation may occur in pulmonary hypertension or connective tissue disorders and is visible on imaging studies (CT, MRI, echocardiography).

    • Valve Disorders: Pulmonary valve stenosis or regurgitation affects flow through the trunk and may lead to post-stenotic dilation or backward flow into the right ventricle.

    Assessment of the pulmonary trunk is routinely performed using echocardiography, CT angiography, and cardiac MRI. Early recognition of abnormalities is critical for preventing right-sided heart failure and improving outcomes in cardiopulmonary disease.

    Did you know? The heart is about the size of your fist and weighs less than a pound.