The subclavian vein is a major blood vessel situated in the upper chest, playing a significant role in the body’s circulatory system. There are two veins, one on each side, located just beneath the collarbone. They return deoxygenated blood from the upper extremities, head, and neck to the heart. Their consistent anatomical position and relatively large diameter make them important in both normal physiological function and various medical procedures.
Precise Anatomical Placement
Each subclavian vein originates as a continuation of the axillary vein in the armpit. This transition occurs at the outer border of the first rib. From this point, the subclavian vein arches upward and then curves downward, running beneath the clavicle. It passes over the first rib in a groove and lies anterior to the anterior scalene muscle.
The subclavian vein is separated from the subclavian artery by the anterior scalene muscle; the vein is anterior to this muscle, while the artery is posterior. This relationship forms the scalene triangle. The vein continues towards the sternal notch, until it reaches the medial border of the anterior scalene muscle.
At this junction, it unites with the internal jugular vein, which descends from the neck, to form the brachiocephalic vein. This union, often termed the venous angle, is also where lymphatic ducts drain into the bloodstream, with the thoracic duct joining the left subclavian vein and the right lymphatic duct joining the right subclavian vein.
Functional Role in the Body
The primary function of the subclavian veins is to collect deoxygenated blood from the upper parts of the body and transport it back to the heart. They receive blood from the axillary veins, which drain the arms and hands. They also receive blood from other veins in the neck and shoulder region, including the external jugular vein.
Once blood flows into the subclavian veins, it empties into the brachiocephalic veins, formed by the union of the subclavian and internal jugular veins. These brachiocephalic veins then merge to form the superior vena cava, which is a large vein that delivers deoxygenated blood directly into the right atrium of the heart.
Importance in Medical Procedures
The subclavian vein’s anatomical position makes it a frequent site for various medical interventions. It is commonly used for central venous catheterization, where a catheter is inserted into a large vein to administer medications, fluids, or for monitoring central venous pressure. Its relatively large diameter and consistent location contribute to its suitability for these procedures.
Healthcare providers also use the subclavian vein for inserting pacemaker leads to regulate heart rhythm. It can also be accessed for dialysis, particularly when other sites are unavailable, though this use is restricted due to stenosis risk. While its location offers accessibility, considerations like proximity to the lung can lead to complications such as pneumothorax (collapsed lung) during catheter insertion. There is also a risk of injuring the subclavian artery or brachial plexus due to their close proximity. To minimize these risks, precise anatomical knowledge and techniques like ultrasound guidance are used.