The superior thoracic artery is a small blood vessel that typically arises from the first part of the axillary artery. It is often one of the first branches of the axillary artery, though its origin can sometimes vary slightly. This artery supplies blood to the upper thoracic wall and portions of the pectoral muscles.
Location
The superior thoracic artery is located near the upper chest and shoulder region. It originates from the first section of the axillary artery, which is located in the axilla (armpit) area. The artery runs along the anterior aspect of the thoracic cage and extends towards the first and second intercostal spaces.
Structure and Anatomy
Origin
The superior thoracic artery arises from the first part of the axillary artery, which is a continuation of the subclavian artery as it passes the lateral border of the first rib. It is typically the first branch of the axillary artery but can sometimes vary in its point of origin, either arising directly from the axillary artery or, less commonly, from nearby arteries.
Course
Once it originates from the axillary artery, the superior thoracic artery descends medially and inferiorly along the upper part of the thoracic wall. It courses forward along the border of the first rib and clavicle, traveling deep to the pectoralis major and superficial to the second intercostal space.
Relations
- Superiorly: It lies near the clavicle and the first rib.
- Inferiorly: It passes over the upper two intercostal spaces.
- Medially: It runs close to the lateral border of the sternum and the upper portion of the thoracic wall.
- Laterally: It is in proximity to the axillary vein and other branches of the axillary artery.
Branches
The superior thoracic artery may give off small branches to the upper intercostal muscles, particularly those in the first and second intercostal spaces. It also sends branches to the pectoralis muscles and occasionally anastomoses (connects) with intercostal arteries or other thoracic vessels.
Termination
The superior thoracic artery terminates by dividing into several smaller branches that supply the pectoral muscles and portions of the upper thoracic wall. These branches sometimes create anastomoses with the internal thoracic artery or other nearby vessels.
Anastomoses
Though not extensively involved in major anastomoses, the superior thoracic artery may occasionally connect with the internal thoracic artery, lateral thoracic artery, or the intercostal arteries in the upper thoracic region, ensuring blood supply continuity to the region.
Function
Blood Supply to the Pectoral Muscles
The primary function of the superior thoracic artery is to supply blood to the pectoral muscles, specifically the pectoralis major and minor. These muscles are essential for movements of the shoulder, such as flexion, adduction, and medial rotation of the humerus. The superior thoracic artery provides oxygenated blood to these muscles, ensuring their proper function and endurance during physical activities.
Supply to the Thoracic Wall
The superior thoracic artery also plays a role in supplying blood to the upper part of the thoracic wall, particularly the first and second intercostal spaces. These spaces contain intercostal muscles that assist in breathing by supporting the expansion and contraction of the rib cage during inhalation and exhalation. The artery’s branches ensure adequate oxygenation of these muscles, aiding in respiration.
Support to Subcutaneous Tissue and Skin
The superior thoracic artery also delivers blood to the subcutaneous tissues and skin overlying the upper thoracic region. These tissues are important for providing a protective layer over the chest and for sensation. The blood flow from the superior thoracic artery helps nourish these tissues, promoting skin health and wound healing when necessary.
Anastomoses and Collateral Circulation
Though relatively small, the superior thoracic artery contributes to anastomoses with other nearby arteries such as the internal thoracic artery and intercostal arteries. These connections help establish collateral circulation in the event of arterial occlusion or injury, ensuring that the surrounding muscles, skin, and thoracic wall maintain an adequate blood supply.
Clinical Significance
The superior thoracic artery, though small, plays an important role in surgical procedures and trauma management involving the upper chest and axillary region. It provides critical blood supply to the pectoral muscles and upper thoracic wall, making it essential for the vitality of these tissues. In surgical procedures, such as mastectomies, axillary lymph node dissections, or pectoral muscle surgeries, care must be taken to avoid damage to the artery to prevent excessive bleeding or compromise of blood flow to the region.
In cases of trauma, such as fractures to the first rib or clavicle, the artery can be at risk of injury. This can lead to hemorrhage, hematoma formation, or compromised blood flow to the chest wall and muscles. Additionally, understanding its anastomoses with the internal thoracic and intercostal arteries is crucial for maintaining collateral circulation during vascular surgeries or in cases of arterial blockage.
Due to its small size, the superior thoracic artery is less commonly involved in pathological conditions like aneurysms or atherosclerosis, but its role in supplying blood to the surrounding musculature and tissue makes it clinically relevant in thoracic and reconstructive surgeries.
