Thoraco-acromial artery

The thoraco-acromial artery is a short but important branch of the axillary artery, which supplies blood to several muscles and structures in the upper chest, shoulder, and deltoid region. It branches into four key divisions: the pectoral, acromial, clavicular, and deltoid branches, which provide vascularization to their respective areas.

Location

The thoraco-acromial artery arises from the second part of the axillary artery, typically just posterior to the pectoralis minor muscle. It pierces the clavipectoral fascia, a dense layer of connective tissue located between the pectoralis major and minor muscles, and divides into its four branches. The artery extends upward and outward, supplying the shoulder region, including the pectoralis muscles, acromion, clavicle, and deltoid muscle. Each branch travels to its specific target area, ensuring that the thoracic and acromial regions receive adequate blood supply.

Structure and Anatomy

The thoraco-acromial artery is a significant branch of the axillary artery, providing blood supply to multiple structures in the chest, shoulder, and upper arm. Below is a detailed description of its anatomy, including its origin, course, branches, and relationships with surrounding structures.

Origin

The thoraco-acromial artery originates from the second part of the axillary artery, which is a continuation of the subclavian artery. The second part of the axillary artery lies deep to the pectoralis minor muscle, and the thoraco-acromial artery arises just posterior to the lower border of this muscle. It is one of several branches of the axillary artery that supplies blood to the chest and shoulder regions.

Course

After originating from the axillary artery, the thoraco-acromial artery quickly pierces the clavipectoral fascia—a layer of connective tissue that extends between the clavicle and the pectoralis minor. Once it passes through this fascia, it branches into its four main divisions: the pectoral, acromial, clavicular, and deltoid branches. These branches extend in various directions to supply different parts of the shoulder, chest, and upper arm.

Piercing the Clavipectoral Fascia

As the thoraco-acromial artery emerges from the axillary artery, it pierces the clavipectoral fascia, which lies beneath the pectoralis major muscle. This fascia is an important landmark for surgeons because it forms a barrier between the pectoralis minor and major muscles. The artery then becomes more superficial, dividing into its four distinct branches.

Distribution Across the Shoulder and Thoracic Region

After piercing the clavipectoral fascia, the thoraco-acromial artery divides into its branches, each taking a specific course to its target area. Each branch is named according to the area it supplies.

Branches

The thoraco-acromial artery has four main branches: the pectoral, acromial, clavicular, and deltoid branches. Each branch supplies different structures in the chest, shoulder, and upper arm.

Pectoral Branch

The pectoral branch is typically the largest of the thoraco-acromial artery’s branches and descends toward the pectoralis major and pectoralis minor muscles.

• Course: The pectoral branch runs downward between the pectoralis major and pectoralis minor muscles, providing numerous branches to both muscles.
• Supplied Structures: It supplies blood to the pectoralis major and minor muscles and may also give small branches to the breast, especially in females, contributing to the blood supply of the breast tissue.

Acromial Branch

The acromial branch travels laterally and superiorly toward the acromion, a bony process of the scapula that forms the highest point of the shoulder.

• Course: The acromial branch runs laterally over the coracoid process and toward the acromion. It courses across the upper part of the deltoid muscle, sometimes forming an anastomosis with branches of the suprascapular artery and the posterior circumflex humeral artery.
• Supplied Structures: This branch supplies blood to the acromion, the upper part of the deltoid muscle, and the shoulder joint.

Clavicular Branch

The clavicular branch is the smallest branch of the thoraco-acromial artery and ascends toward the clavicle and the sternoclavicular joint.

• Course: This branch runs upward, traveling along the inferior surface of the clavicle.
• Supplied Structures: The clavicular branch supplies blood to the sternoclavicular joint, the nearby fascia, and the subclavius muscle, which lies just below the clavicle.

Deltoid Branch

The deltoid branch runs laterally toward the deltoid muscle, following the cephalic vein in the deltopectoral groove (the space between the deltoid and pectoralis major muscles).

• Course: This branch runs along the deltopectoral groove, which lies between the deltoid and pectoralis major muscles, often accompanying the cephalic vein.
• Supplied Structures: The deltoid branch supplies blood to the deltoid muscle and parts of the pectoralis major muscle.

Relationships to Surrounding Structures

The thoraco-acromial artery is closely related to several important anatomical structures in the chest and shoulder region. These relationships are important to consider during surgeries and medical procedures involving the axillary region.

Axillary Artery

The thoraco-acromial artery is a branch of the axillary artery, arising from its second part, which is located deep to the pectoralis minor muscle. The axillary artery is the primary vessel that supplies the upper limb and is divided into three parts by the pectoralis minor muscle. The thoraco-acromial artery is one of several branches from the second part of the axillary artery.

Clavipectoral Fascia

The thoraco-acromial artery passes through the clavipectoral fascia, a dense layer of connective tissue that lies between the pectoralis major and minor muscles. This fascia is a key anatomical landmark and forms a barrier that the artery must penetrate to reach its target areas. The fascia serves as an important reference point during surgical procedures in the axillary region.

Pectoralis Major and Minor Muscles

The thoraco-acromial artery provides blood to the pectoralis major and pectoralis minor muscles via its pectoral branch. These muscles are involved in shoulder movement, and their vascular supply is crucial for their function. The artery runs between these two muscles before dividing into its branches.

Cephalic Vein

The deltoid branch of the thoraco-acromial artery follows the cephalic vein in the deltopectoral groove. This close relationship is important because the cephalic vein is a key superficial vein often used in venous access or during surgical procedures.

Acromion and Shoulder Joint

The acromial branch of the thoraco-acromial artery supplies the acromion and parts of the shoulder joint. It travels over the coracoid process of the scapula and forms anastomoses with other arteries supplying the shoulder joint, such as the suprascapular artery and posterior circumflex humeral artery.

Anastomoses

The thoraco-acromial artery forms several important anastomoses (connections) with other arteries in the shoulder and chest regions, ensuring a continuous blood supply to these areas.

• Acromial Branch Anastomoses: The acromial branch of the thoraco-acromial artery often forms anastomoses with the suprascapular artery and the posterior circumflex humeral artery, which help supply the acromion and shoulder joint.
• Deltoid Branch Anastomoses: The deltoid branch may form anastomoses with branches of the brachial artery or posterior circumflex humeral artery, providing an alternative blood supply to the deltoid muscle.

Variations

Anatomical variations in the thoraco-acromial artery are relatively common. Some of the most notable variations include:

• Branching Pattern: The number of branches and their distribution can vary. For example, in some individuals, the pectoral branch may be more prominent, while in others, the deltoid or acromial branches may be larger.
• Point of Origin: The point of origin of the thoraco-acromial artery can vary slightly. In some cases, it may arise higher or lower along the axillary artery, or it may share a common trunk with other nearby arteries.

Function

The thoraco-acromial artery plays a critical role in supplying blood to the structures of the upper chest, shoulder, and upper arm. Its branches provide vital oxygen and nutrients to muscles, bones, joints, and skin in these regions. Below is a detailed description of the specific functions of each branch of the thoraco-acromial artery.

Blood Supply to the Pectoral Muscles

The pectoral branch of the thoraco-acromial artery is responsible for supplying blood to both the pectoralis major and pectoralis minor muscles.

• Nourishment of the Pectoralis Major Muscle: The pectoral branch delivers oxygenated blood to the pectoralis major, which is a large, superficial muscle involved in adduction, internal rotation, and flexion of the arm. This blood supply is essential for the muscle’s function during movements such as pushing or lifting.
• Nourishment of the Pectoralis Minor Muscle: The pectoralis minor, located beneath the pectoralis major, helps stabilize the scapula by drawing it anteriorly and inferiorly. The pectoral branch ensures that this muscle remains functional by providing a continuous blood supply, which is crucial for shoulder stability.

Blood Supply to the Acromion and Shoulder Joint

The acromial branch of the thoraco-acromial artery is responsible for vascularizing the acromion and the surrounding shoulder region.

• Nourishment of the Acromion and Deltoid Muscle: The acromion, a bony process of the scapula, plays a significant role in shoulder stability. The acromial branch supplies blood to this bony structure and the surrounding soft tissues, including the deltoid muscle, which covers the shoulder. The deltoid is involved in abduction, flexion, and extension of the arm, and its blood supply is critical for maintaining shoulder mobility and strength.
• Contribution to the Shoulder Joint: The acromial branch also contributes to the vascularization of the shoulder joint, ensuring that the connective tissues and cartilage in the joint receive adequate oxygen and nutrients. This helps maintain joint health and flexibility.

Blood Supply to the Clavicle and Sternoclavicular Joint

The clavicular branch of the thoraco-acromial artery provides blood to the clavicle and sternoclavicular joint.

• Nourishment of the Clavicle: The clavicular branch supplies the clavicle (collarbone), an important bone for shoulder stability and upper limb movements. The clavicle acts as a strut between the scapula and sternum, and its blood supply is essential for maintaining bone strength and supporting its function during shoulder movements.
• Sternoclavicular Joint: The clavicular branch also vascularizes the sternoclavicular joint, where the clavicle meets the sternum. This joint allows movement of the clavicle, which is critical for the mobility of the shoulder girdle. Adequate blood flow to this joint helps maintain its function and prevent degeneration.

Blood Supply to the Deltoid Muscle

The deltoid branch of the thoraco-acromial artery supplies the deltoid muscle, which covers the shoulder and is involved in various arm movements.

• Nourishment of the Deltoid Muscle: The deltoid branch follows the cephalic vein in the deltopectoral groove and provides oxygenated blood to the deltoid muscle. The deltoid is responsible for abducting the arm, as well as assisting in flexion, extension, and rotation of the shoulder. The continuous blood supply from the deltoid branch supports these functions and ensures that the muscle has the energy it needs for movement.
• Support for Shoulder Movement: By delivering blood to the deltoid muscle, the deltoid branch enables movements such as lifting the arm away from the body and performing overhead tasks, which are crucial for everyday activities.

Oxygen and Nutrient Delivery to Surrounding Tissues

Like all arteries, the thoraco-acromial artery delivers essential oxygen and nutrients to the tissues it supplies. This function is fundamental for maintaining the health, repair, and regeneration of muscles, bones, joints, and skin.

• Muscle Function and Endurance: The oxygenated blood supplied by the thoraco-acromial artery ensures that the muscles in the chest and shoulder region, including the pectoralis major, pectoralis minor, and deltoid, can maintain their strength and endurance during physical activities.
• Tissue Repair and Healing: After injury, surgery, or muscle strain, the branches of the thoraco-acromial artery provide the necessary nutrients for tissue repair and healing. This blood flow is crucial for muscle recovery, joint health, and skin regeneration.

Collateral Circulation and Anastomoses

The branches of the thoraco-acromial artery contribute to collateral circulation in the chest and shoulder regions. Collateral circulation ensures that blood flow continues even if one artery is compromised, preventing ischemia in the muscles and bones.

• Anastomoses with Other Arteries: The acromial branch of the thoraco-acromial artery forms anastomoses with the suprascapular artery and the posterior circumflex humeral artery. These connections provide alternative routes for blood flow to the acromion and shoulder joint, ensuring that these areas remain well-supplied with blood during movement or injury.
• Anastomoses in the Deltoid Region: The deltoid branch may anastomose with branches of the brachial artery or posterior circumflex humeral artery, providing additional blood flow to the deltoid muscle. This ensures that the muscle can function properly during shoulder and arm movements, even if one of the primary vessels is blocked.

Clinical Significance

The thoraco-acromial artery is clinically significant due to its role in supplying critical blood flow to the shoulder and chest regions, particularly the pectoral and deltoid muscles, the acromion, and the clavicle.

• Surgical Importance: The thoraco-acromial artery is often encountered in surgical procedures involving the shoulder, such as shoulder arthroscopy, breast surgery, or clavicle repair. Its proximity to key structures means that surgeons must be careful to avoid damaging the artery to prevent bleeding or impaired blood supply to surrounding tissues.
• Trauma and Injury: Injuries to the shoulder or chest, such as fractures of the clavicle or acromion, can potentially damage the branches of the thoraco-acromial artery, leading to hematomas or compromised blood flow to muscles like the pectoralis major and deltoid.
• Collateral Circulation: The artery’s branches form important anastomoses with other arteries in the region, such as the suprascapular and posterior circumflex humeral arteries, providing crucial collateral circulation to the shoulder and chest. This is particularly significant in cases where primary arteries are compromised.