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    From Cardiovascular System

    Left Subclavian Artery
    Supplies the left upper limb.
    Radial Arteries
    Supply the lateral aspect of the forearm and hand.
    Brachial Arteries
    Major artery of the upper arm.
    Interventricular Septum
    Wall separating the left and right ventricles.
    Crista Terminalis
    Smooth muscular ridge in the right atrium.
    Common Iliac Veins
    Drain blood from the pelvis and lower limbs.
    Anterior Cardiac Veins
    Drain directly into the right atrium.
    Chordae Tendineae
    Tendon-like cords attaching valve leaflets to papillary muscles.
    Right Ventricle
    Pumps blood to the lungs via pulmonary artery.
    Auricles
    Small muscular pouches of each atrium.
    Ulnar Arteries
    Supply the medial aspect of the forearm and hand.
    Femoral Arteries
    Main arteries supplying the thighs.
    Small Cardiac Vein
    Drains right atrium and ventricle.
    Left Atrium
    Receives oxygenated blood from the lungs.
    Marginal Branch
    Supplies right ventricle along the margin.
    Common Iliac Arteries
    Branch from abdominal aorta to supply the lower limbs.
    Dorsal Venous Arch
    Superficial venous network on the dorsum of the foot.
    Trabeculae Carneae
    Irregular muscular columns on the walls of the ventricles.
    Parietal Layer
    Lines the internal surface of the fibrous pericardium.
    Fossa Ovalis
    Remnant of the fetal foramen ovale.
    Median Cubital Vein
    Connects cephalic and basilic veins at the elbow.
    Left Coronary Artery
    Supplies blood to left side of heart.
    External Carotid Artery
    Supplies blood to the face and scalp.
    Left Common Carotid Artery
    Supplies the head and neck.
    Descending Aorta
    Portion of the aorta descending through thorax and abdomen.

    Left Pulmonary Artery

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    Carries blood to left lung.

    Overview

    The left pulmonary artery is one of the two main branches of the pulmonary trunk and plays a vital role in pulmonary circulation. It carries deoxygenated blood from the right ventricle of the heart to the left lung for oxygenation. Despite being an artery, it uniquely carries oxygen-poor blood — a distinguishing characteristic of pulmonary arteries compared to systemic arteries. Its function is critical in maintaining proper gas exchange and supporting systemic oxygen delivery.

    Location

    The left pulmonary artery arises from the pulmonary trunk, which exits the right ventricle of the heart. It originates just after the bifurcation of the pulmonary trunk, at approximately the level of the T5 vertebra. From there, it travels horizontally to the left, passing anterior to the descending aorta and posterior to the left atrial appendage. It enters the hilum of the left lung superior to the main bronchus and divides into branches that supply the superior and inferior lobes of the lung.

    Structure

    The left pulmonary artery is a large, elastic blood vessel designed to handle the output of the right ventricle. Its structure includes:

    • Origin: Arises from the bifurcation of the pulmonary trunk.

    • Course: Shorter and more horizontal than the right pulmonary artery, coursing to the left lung hilum.

    • Hilum Entry: Enters the lung at the hilum, where it lies superior to the pulmonary veins and anterior to the left main bronchus.

    • Branches: Divides into the left superior pulmonary artery and left inferior pulmonary artery, each of which further branches into segmental arteries supplying the bronchopulmonary segments of the left lung.

    The walls of the artery contain elastic tissue and smooth muscle, allowing it to stretch with the pulsatile flow of blood and help regulate pulmonary vascular resistance.

    Function

    The primary function of the left pulmonary artery is to transport deoxygenated blood from the right side of the heart to the alveoli of the left lung. Within the lung, this blood undergoes gas exchange, releasing carbon dioxide and absorbing oxygen. The oxygenated blood then returns to the heart via the left pulmonary veins, ready to be pumped into the systemic circulation.

    This function is essential for maintaining oxygen levels in the bloodstream and removing metabolic waste in the form of carbon dioxide.

    Physiological Role(s)

    The left pulmonary artery contributes to multiple physiological processes beyond simple blood transport:

    • Gas Exchange Facilitation: Delivers deoxygenated blood directly to the alveolar capillaries of the left lung, enabling rapid and efficient gas exchange.

    • V/Q Matching: Plays a key role in ventilation-perfusion (V/Q) matching, which ensures blood flow is directed to the most ventilated areas of the lung, maximizing respiratory efficiency.

    • Pulmonary Vascular Resistance Regulation: The artery participates in vasomotor responses such as hypoxic pulmonary vasoconstriction, adjusting blood flow based on oxygen availability.

    • Developmental Circulation (Fetal Life): In the fetus, the left pulmonary artery is connected to the descending aorta via the ductus arteriosus, allowing most of the right ventricular output to bypass the non-functioning fetal lungs.

    Clinical Significance

    The left pulmonary artery is involved in numerous clinical conditions and is an important structure in both diagnostic and surgical contexts:

    • Pulmonary Embolism (PE): A thrombus may lodge in the left pulmonary artery, blocking blood flow to the left lung and impairing gas exchange. CT pulmonary angiography is the gold standard for diagnosis.

    • Pulmonary Hypertension: Chronic pressure overload in the pulmonary arteries, including the left, can lead to right ventricular hypertrophy and heart failure.

    • Congenital Heart Defects: Abnormal development of the left pulmonary artery may occur in conditions such as pulmonary atresia or truncus arteriosus. In rare cases, pulmonary artery sling may result from anomalous origin and course, causing airway compression.

    • Surgical Relevance: The left pulmonary artery must be carefully preserved or ligated during lung resections (e.g., pneumonectomy or lobectomy). Inadequate management can lead to life-threatening hemorrhage or infarction.

    • Pulmonary Artery Catheterization: Invasive monitoring via a Swan-Ganz catheter involves navigating through the pulmonary arteries, including the left, to assess pulmonary artery pressures and cardiac output.

    • Post-Ablation Pulmonary Vein Stenosis: Though this primarily affects pulmonary veins, anatomical proximity means the left pulmonary artery may be visualized during ablation planning and should be preserved.

    Imaging modalities such as chest X-ray, CT, MRI, echocardiography, and angiography are essential for evaluating left pulmonary artery anatomy, patency, and pathology. Treatment depends on the underlying condition and may include anticoagulation, surgical repair, or targeted pulmonary vasodilator therapy.

    Did you know? The right side of the heart pumps oxygen-poor blood to the lungs, while the left side pumps oxygen-rich blood to the rest of the body.