Thoracodorsal artery

The thoracodorsal artery is a branch of the subscapular artery, which itself arises from the third part of the axillary artery. It is an important artery that supplies blood to the latissimus dorsi muscle, parts of the serratus anterior, and other structures in the lateral and posterior thoracic wall. It plays a key role in the vascular supply of muscles that are involved in movements of the upper limb, especially during actions like pulling or lifting.

Location

The thoracodorsal artery originates from the subscapular artery, usually at the level of the inferior border of the subscapularis muscle. It descends along the lateral thoracic wall, running deep to the latissimus dorsi muscle. The artery follows the path of the thoracodorsal nerve as it travels toward the inferior angle of the scapula, supplying blood to the latissimus dorsi and nearby structures. It terminates near the lateral edge of the thoracic wall, where it provides branches to the surrounding muscles and tissues.

Structure and Anatomy

The thoracodorsal artery is an important vessel in the vascular supply of the posterior and lateral thoracic wall and the muscles associated with the scapula and upper limb. Below is a detailed description of the origin, course, branches, and relationships of the thoracodorsal artery with surrounding structures.

Origin

The thoracodorsal artery arises from the subscapular artery, which is a major branch of the axillary artery. The subscapular artery arises from the third part of the axillary artery and supplies blood to the scapular and thoracic regions. The thoracodorsal artery originates from the distal portion of the subscapular artery, near the lower margin of the subscapularis muscle. It is one of two major branches of the subscapular artery, the other being the circumflex scapular artery.

Course

After originating from the subscapular artery, the thoracodorsal artery travels downward along the lateral aspect of the thoracic wall. Its course takes it close to the muscles and structures of the posterior axilla and the lower scapular region.

Descent Along the Lateral Thoracic Wall

The thoracodorsal artery descends along the lateral edge of the thoracic wall, running deep to the latissimus dorsi muscle. The artery typically follows the path of the thoracodorsal nerve, which innervates the latissimus dorsi. As the artery descends, it remains lateral to the rib cage and is closely associated with the axillary structures.

Relationship with the Thoracodorsal Nerve: The artery runs in close proximity to the thoracodorsal nerve, which arises from the posterior cord of the brachial plexus. Together, the artery and nerve travel to the latissimus dorsi muscle to supply both vascular and nervous input.

Approaching the Inferior Angle of the Scapula

As the thoracodorsal artery approaches the lower portion of the scapula, near the inferior angle, it continues to supply blood to the latissimus dorsi and surrounding muscles. The artery is located deep within the thoracic wall and terminates by providing branches to various muscles and tissues in the area.

Branches

The thoracodorsal artery gives off several small branches that supply nearby muscles and structures, ensuring that the posterior and lateral thoracic regions receive an adequate blood supply.

Muscular Branches

The thoracodorsal artery provides numerous muscular branches to the following muscles:

• Latissimus Dorsi: The main muscle supplied by the thoracodorsal artery, the latissimus dorsi is involved in the movement of the upper limb, particularly in actions such as pulling, extension, adduction, and internal rotation of the shoulder.
• Subscapularis: The thoracodorsal artery provides branches to the subscapularis muscle, which is part of the rotator cuff group and functions in internal rotation of the shoulder.
• Serratus Anterior: The artery also supplies parts of the serratus anterior, a muscle that helps in protracting the scapula and stabilizing it during arm movements.

Cutaneous Branches

In addition to supplying the deep muscles, the thoracodorsal artery gives off small cutaneous branches that supply the skin over the lateral thoracic wall. These branches help vascularize the skin and subcutaneous tissues in the axillary and scapular regions.

Termination

The thoracodorsal artery continues its course toward the inferior angle of the scapula, where it provides terminal branches that supply the lower part of the latissimus dorsi muscle and surrounding tissues. It eventually anastomoses with other arteries in the region to form part of the collateral circulation of the thoracic and scapular areas.

Relationship to Surrounding Structures

The thoracodorsal artery is closely related to several important anatomical structures, particularly muscles and nerves of the thoracic wall and axillary region.

• Thoracodorsal Nerve: The thoracodorsal artery runs alongside the thoracodorsal nerve, which is a branch of the posterior cord of the brachial plexus. This nerve innervates the latissimus dorsi muscle, and its close proximity to the artery ensures that both vascular and nervous supplies reach the muscle simultaneously.
• Axillary Structures: The thoracodorsal artery is closely associated with the structures of the axilla, including the axillary artery, veins, and nerves. It originates from the subscapular artery, a major branch of the axillary artery, and runs through the posterior axillary wall.
• Scapula: The thoracodorsal artery’s course brings it close to the scapula, particularly the inferior angle. Its branches help supply the muscles that attach to the scapula, including the latissimus dorsi and serratus anterior.

Anastomoses

The thoracodorsal artery forms important anastomoses with other arteries that supply the thoracic and scapular regions. These anastomotic connections ensure adequate blood flow to the muscles and skin of the lateral and posterior thoracic wall, even if one artery is compromised.

• Circumflex Scapular Artery: One of the key anastomotic connections is with the circumflex scapular artery, another branch of the subscapular artery. This anastomosis helps maintain blood flow to the scapular region and provides collateral circulation.
• Intercostal Arteries: The thoracodorsal artery may also form small anastomoses with the posterior intercostal arteries, which supply blood to the thoracic wall. These connections help provide additional blood flow to the muscles and skin over the ribs and thorax.

Variations

Anatomical variations in the thoracodorsal artery are uncommon, but some individuals may exhibit minor differences in the size or course of the artery. In rare cases, the artery may arise directly from the axillary artery or may have additional branches that supply more extensive areas of the thoracic wall.

Function

The thoracodorsal artery plays a crucial role in supplying blood to the muscles and tissues in the posterior axillary and thoracic regions. Its function is essential for maintaining the health and function of the muscles involved in shoulder and upper limb movements, as well as providing oxygen and nutrients to the skin and subcutaneous tissues. Below is a detailed description of its functions.

Blood Supply to the Latissimus Dorsi Muscle

The primary function of the thoracodorsal artery is to supply oxygenated blood to the latissimus dorsi muscle, one of the largest muscles in the back, which plays a vital role in upper limb movement.

• Nourishment of the Latissimus Dorsi: The thoracodorsal artery provides the main blood supply to the latissimus dorsi muscle. This muscle is responsible for shoulder movements such as extension, adduction, and internal rotation of the arm. The artery ensures that the latissimus dorsi receives enough oxygen and nutrients to perform these movements efficiently.
• Support for Upper Limb Movement: The artery’s blood supply enables the latissimus dorsi to function properly during activities that involve pulling or lifting, such as climbing, pulling objects toward the body, and swimming. The muscle’s ability to exert strong force is dependent on the continuous blood flow provided by the thoracodorsal artery.

Blood Supply to the Subscapularis Muscle

The thoracodorsal artery also supplies blood to the subscapularis muscle, a key component of the rotator cuff group that helps stabilize the shoulder joint and assists in the internal rotation of the arm.

• Nourishment of the Subscapularis: The subscapularis muscle is located on the anterior surface of the scapula and is involved in the internal rotation of the shoulder. The thoracodorsal artery provides important branches that deliver oxygenated blood to this muscle, ensuring its proper function and health.
• Support for Shoulder Stability: By maintaining the blood supply to the subscapularis, the thoracodorsal artery helps support the stability of the shoulder joint, especially during activities that require rotation or stabilization of the arm.

Blood Supply to the Serratus Anterior Muscle

Another important function of the thoracodorsal artery is to supply the serratus anterior muscle, which plays a critical role in the movement and stabilization of the scapula (shoulder blade).

• Scapular Stabilization: The serratus anterior muscle is essential for protracting the scapula, meaning it helps move the scapula forward and stabilize it against the rib cage. The thoracodorsal artery delivers the necessary blood flow to the lower fibers of the serratus anterior, allowing it to perform this function.
• Support for Overhead Movements: The artery’s blood supply to the serratus anterior is crucial for movements that involve lifting the arms overhead, such as pushing, pulling, or lifting objects. The stability of the scapula, ensured by the serratus anterior, depends on the muscle’s proper blood supply.

Blood Supply to the Skin and Superficial Tissues

The thoracodorsal artery provides cutaneous branches that supply the skin and subcutaneous tissues over the lateral thoracic wall and the axillary region.

• Nourishment of the Skin: The artery delivers blood to the skin over the lateral thoracic wall and posterior axillary region, ensuring that the skin remains healthy, well-nourished, and capable of healing. This blood flow is essential for maintaining the elasticity, hydration, and integrity of the skin in these areas.
• Support for Wound Healing: In cases of injury, surgery, or trauma to the skin and subcutaneous tissues of the axillary or thoracic regions, the blood supply from the thoracodorsal artery plays a critical role in tissue repair and wound healing.

Contribution to Collateral Circulation

The thoracodorsal artery contributes to the collateral circulation in the scapular and thoracic regions, forming important anastomoses with other arteries to maintain continuous blood flow to these areas.

• Anastomosis with Circumflex Scapular Artery: One of the primary anastomotic connections formed by the thoracodorsal artery is with the circumflex scapular artery, another branch of the subscapular artery. This anastomosis ensures that the muscles and tissues in the scapular region, particularly the latissimus dorsi and serratus anterior, receive a robust blood supply even if one artery is compromised.
• Support During Movement: The anastomotic network involving the thoracodorsal artery helps maintain adequate blood flow to the muscles and tissues during shoulder and upper limb movements, which could otherwise compress or temporarily obstruct blood flow in certain arteries. This collateral circulation is vital for preventing ischemia (lack of blood flow) in the muscles and skin.

Oxygen and Nutrient Delivery

Like all arteries, the fundamental role of the thoracodorsal artery is to deliver oxygen and essential nutrients to the tissues it supplies. This function is critical for maintaining the health, function, and repair of muscles, skin, and bones in the scapular and thoracic regions.

• Muscle Function and Endurance: The continuous delivery of oxygen and nutrients to the latissimus dorsi, subscapularis, and serratus anterior muscles ensures that they can maintain their strength, endurance, and ability to contract during physical activity. Without adequate blood flow, these muscles would become fatigued and unable to perform their roles in shoulder and upper limb movement.
• Tissue Repair and Maintenance: The blood supply from the thoracodorsal artery is essential for tissue repair, particularly after muscle strain, injury, or surgery. The oxygen and nutrients delivered by the artery support tissue regeneration and healing in the affected muscles and skin.

Support for Surgical and Reconstructive Procedures

The thoracodorsal artery is often used in reconstructive surgery, particularly in procedures that require vascularized tissue grafts, such as the latissimus dorsi flap.

Vascularization of Tissue Flaps: During reconstructive surgeries, such as breast reconstruction or covering large tissue defects, the thoracodorsal artery is used to supply blood to the latissimus dorsi muscle, which is transferred as a flap to other parts of the body. The artery’s ability to maintain vascularization of the muscle ensures the survival and integration of the tissue graft.

Clinical Significance

The thoracodorsal artery is clinically significant due to its vital role in supplying blood to the latissimus dorsi muscle and its involvement in several surgical procedures. Key points include:

• Reconstructive Surgery: The thoracodorsal artery is commonly used in latissimus dorsi flap procedures, where the latissimus dorsi muscle, along with its blood supply, is transferred to other parts of the body for reconstruction. This is particularly important in breast reconstruction following mastectomy and in repairing large tissue defects. The artery’s ability to maintain blood flow to the muscle flap ensures the success of these procedures.
• Shoulder and Thoracic Injuries: Injury to the thoracodorsal artery, such as from trauma or during axillary surgeries, can compromise blood flow to the latissimus dorsi and surrounding muscles, leading to impaired function or muscle ischemia.
• Axillary Lymph Node Dissection: During surgical procedures for breast cancer, such as axillary lymph node dissection, the thoracodorsal artery and its accompanying nerve (thoracodorsal nerve) must be preserved to prevent damage to the latissimus dorsi muscle, which could result in functional deficits in shoulder and arm movement.