Subclavian Vein

The subclavian vein is a major vein of the upper thorax that drains blood from the upper limb, shoulder, and part of the head and neck. It is a continuation of the axillary vein and becomes the brachiocephalic vein after joining with the internal jugular vein. Located anterior to the subclavian artery, it plays a vital role in venous return from the upper body.

Origin and Course

The subclavian vein begins as a continuation of the axillary vein at the lateral border of the first rib. It courses medially, arching slightly over the first rib, and ends behind the medial end of the clavicle, where it unites with the internal jugular vein to form the brachiocephalic vein.

Length and Location

Length: Approximately 6–7 cm
Location: Runs anterior and inferior to the subclavian artery, across the first rib

Relations

Clavicle
Sternocleidomastoid muscle (lower part)
Subclavius muscle and clavipectoral fascia

Posterior

Anterior scalene muscle (separates it from the subclavian artery)
First rib

Inferior

First rib and pleura

Superior

Lower part of the neck structures including nerves and lymphatics

Tributaries

External jugular vein (usually joins near the middle of its course)
Thoracic duct (on the left side)
Right lymphatic duct (on the right side)
Occasional small muscular and thoracic wall veins

Course Relative to Scalene Muscles

The subclavian vein lies anterior to the anterior scalene muscle, while the subclavian artery lies posterior to it. This anatomical relationship is important in both clinical procedures and understanding thoracic outlet anatomy.

Function

The subclavian vein drains blood from:

Upper limb (via axillary vein)
Lateral chest wall
External jugular region
Lymphatic return from thoracic duct (left) or right lymphatic duct (right)

Histological Structure

Like other large veins, the subclavian vein has a thin wall and large lumen. Its structure includes:

Tunica intima: Endothelium with a thin subendothelial layer
Tunica media: Thin smooth muscle layer
Tunica adventitia: Thick connective tissue with vasa vasorum

Clinical Significance

Central venous access: The subclavian vein is commonly used for central line placement, but care is required to avoid pneumothorax or arterial puncture
Thoracic outlet syndrome: Compression between the clavicle and first rib can affect venous flow, leading to swelling and cyanosis of the upper limb
Venous thrombosis: Can lead to effort thrombosis (Paget-Schroetter syndrome), especially in athletes or after catheterization

Topographic Summary

Origin: Continuation of axillary vein at lateral border of first rib
Termination: Joins internal jugular vein to form brachiocephalic vein
Side branches: External jugular vein, thoracic duct (left), right lymphatic duct (right)
Location: Anterior to anterior scalene muscle, superior to first rib