The human circulatory system is a vast network of vessels responsible for transporting blood throughout the body. Arteries carry oxygen-rich blood away from the heart, delivering it to tissues and organs. Veins, conversely, collect oxygen-poor blood and waste products, returning this blood to the heart to be re-oxygenated in the lungs.
Its Anatomical Location
The subclavian vein is a paired vessel, located on each side of the body, just beneath the clavicle. Its name, “subclavian,” literally means “under the clavicle,” reflecting its position. This vein begins as a continuation of the axillary vein, which transitions into the subclavian vein at the outer border of the first rib.
From this point, the subclavian vein follows a course medially, passing between the clavicle and the first rib. It lies anterior to the anterior scalene muscle, which separates it from the subclavian artery that runs behind the same muscle. Each subclavian vein then joins with the internal jugular vein on its respective side, forming a larger vessel called the brachiocephalic vein. This junction, often referred to as the venous angle, marks the subclavian vein’s termination. The diameter of the subclavian veins is typically about 1 to 2 centimeters, or roughly the size of a person’s little finger.
Its Role in Circulation
The subclavian vein collects deoxygenated blood from the upper regions of the body. It drains blood primarily from the upper limbs, including the arms and hands, as well as portions of the head and neck. The axillary vein, which collects blood from the upper extremities, flows directly into the subclavian vein. Similarly, the internal and external jugular veins, which gather blood from the head and neck, contribute to the flow into the subclavian vein.
These brachiocephalic veins then unite to create the superior vena cava. The superior vena cava is a large vein that empties directly into the right atrium of the heart, completing the return of deoxygenated blood from the upper body. The left subclavian vein also uniquely receives lymphatic fluid from the thoracic duct, which transports fats and other substances from the digestive system into the bloodstream.
Medical Importance
The subclavian vein is a frequent site for central venous catheters, often called central lines. Healthcare providers use these catheters to deliver medications, administer fluids, or monitor central venous pressure. Its relatively large diameter and predictable anatomical course make it a suitable access point for these interventions.
One common method for accessing this vein is the infraclavicular approach, where the catheter is inserted below the clavicle. While generally effective, procedures involving the subclavian vein require careful attention due to its proximity to the lung, which presents a small possibility of a pneumothorax (collapsed lung). Despite this consideration, subclavian central lines are often associated with a lower risk of infection compared to other central line insertion sites.