Lateral thoracic artery

The lateral thoracic artery is a branch of the second part of the axillary artery. It provides blood to the lateral and anterior thoracic walls, as well as the axillary region. It primarily supplies the serratus anterior muscle, parts of the pectoralis major and minor muscles, and the lateral portion of the breast in females.

Location

The lateral thoracic artery arises from the second part of the axillary artery, near the lower border of the pectoralis minor muscle. It descends along the lateral side of the thorax, following the surface of the serratus anterior muscle. The artery travels along the chest wall, supplying the lateral thoracic region and accompanying the long thoracic nerve. In females, it also provides blood to the lateral aspect of the breast. It lies in close proximity to the axillary lymph nodes and vessels.

Structure and Anatomy

The lateral thoracic artery is an important blood vessel that arises from the axillary artery and supplies the lateral thoracic wall and structures in the axillary region. Below is a detailed description of the lateral thoracic artery’s origin, course, branches, and relationship with surrounding structures.

Origin

The lateral thoracic artery typically originates from the second part of the axillary artery, although its point of origin can vary. It arises near or under the lower border of the pectoralis minor muscle, which crosses over the axillary artery at this level. The axillary artery is divided into three parts, with the lateral thoracic artery originating from the second part, between the first and third parts of the axillary artery.

Variant Origins: In some cases, the lateral thoracic artery may originate from other vessels, such as the thoracoacromial artery, subscapular artery, or even directly from the subclavian artery.

Course

The lateral thoracic artery takes a downward and slightly lateral course along the thoracic wall. It follows the contour of the serratus anterior muscle and is closely associated with the thoracic wall and axillary region.

Descent Along the Thoracic Wall

After arising from the axillary artery, the lateral thoracic artery descends along the lateral aspect of the thoracic wall. It courses over the surface of the serratus anterior muscle, running parallel to the long thoracic nerve, which innervates the serratus anterior muscle.

Relationship with Long Thoracic Nerve: The artery and nerve travel together along the lateral thoracic wall, supplying blood to and innervating the serratus anterior muscle. This proximity is important for ensuring adequate oxygenation and nerve function in this region.

Thoracic and Axillary Course

As the artery continues its descent, it remains closely associated with the pectoralis major and pectoralis minor muscles, supplying their lateral portions. In females, it also gives off branches to supply the lateral aspect of the breast.

Breast Supply in Females: In females, the lateral thoracic artery provides significant vascularization to the lateral portion of the breast, contributing to the overall blood supply along with the internal thoracic artery.

Branches

The lateral thoracic artery gives off several small branches that supply various structures in the lateral thoracic and axillary regions.

Muscular Branches

The lateral thoracic artery provides muscular branches to the following muscles:

• Serratus Anterior: The artery supplies the serratus anterior muscle, which is responsible for the protraction and upward rotation of the scapula. The blood flow provided by the lateral thoracic artery supports the function of this muscle.
• Pectoralis Major and Pectoralis Minor: The artery also supplies the lateral portions of both the pectoralis major and pectoralis minor muscles, which play roles in arm adduction and shoulder stabilization.

Cutaneous Branches

The lateral thoracic artery provides cutaneous branches that supply the skin and superficial tissues of the lateral thoracic wall. These branches help nourish the skin, particularly in the axillary region and lateral chest wall.

Breast Branches (in Females)

In females, the lateral thoracic artery sends branches to the lateral portion of the breast. This contribution to the vascularization of the breast is particularly important for the external areas of the glandular tissue, supporting breast development and function.

Anastomoses with Internal Thoracic Artery: The lateral thoracic artery’s branches to the breast may form anastomoses with branches of the internal thoracic artery, which supplies the medial portion of the breast.

Relationship to Surrounding Structures

The lateral thoracic artery is closely related to several important anatomical structures in the axillary and thoracic regions.

Serratus Anterior Muscle

The lateral thoracic artery runs along the surface of the serratus anterior muscle, which it supplies with blood. The muscle is critical for scapular protraction and stabilization, and its relationship with the artery is essential for maintaining its function.

Long Thoracic Nerve

The artery courses alongside the long thoracic nerve, which innervates the serratus anterior muscle. This close anatomical relationship is important because injury to one structure (such as during trauma or surgery) may affect the other, leading to complications such as winged scapula if the nerve is damaged.

Axillary Lymph Nodes

The lateral thoracic artery is situated near the axillary lymph nodes, which are located within the axilla. These lymph nodes are critical for immune function and drainage of the upper limb and thoracic region. The artery’s proximity to these lymph nodes is important during breast surgeries and axillary lymph node dissections, where preserving the artery is necessary to prevent complications.

Pectoral Muscles

The lateral thoracic artery runs near the pectoralis major and pectoralis minor muscles, supplying their lateral portions with blood. These muscles are involved in various upper limb movements, including shoulder adduction and internal rotation.

Variations

Anatomical variations in the lateral thoracic artery are not uncommon. Some of these variations include:

• Origin Variations: As mentioned, the lateral thoracic artery may arise from different points other than the second part of the axillary artery. It may originate from the thoracoacromial artery, subscapular artery, or directly from the subclavian artery.
• Course Variations: In some individuals, the lateral thoracic artery may take a slightly different course, traveling closer to or farther from the thoracic wall.
• Size and Branching: The size and number of branches of the lateral thoracic artery can vary. In some cases, the artery may be larger, supplying a more extensive area of the thoracic wall, while in others, it may be smaller or have fewer branches.

Function

The lateral thoracic artery plays a critical role in the vascular supply of the lateral thoracic wall, axillary region, and, in females, the breast. Its primary function is to deliver oxygenated blood to muscles, skin, and other soft tissues in these areas. Below is a detailed breakdown of the specific functions of the lateral thoracic artery.

Blood Supply to the Serratus Anterior Muscle

One of the main functions of the lateral thoracic artery is to supply blood to the serratus anterior muscle.

• Nourishment of the Serratus Anterior: The serratus anterior is responsible for protracting the scapula (pulling the shoulder blade forward) and upward rotation of the scapula, which is essential for lifting the arms above the head. The lateral thoracic artery supplies oxygen and nutrients to this muscle, enabling it to perform its functions effectively.
• Support for Shoulder Movement: By providing a steady blood supply to the serratus anterior, the lateral thoracic artery helps maintain proper scapular movement and stability during activities such as pushing or lifting.

Blood Supply to the Pectoralis Major and Minor Muscles

The lateral thoracic artery also provides blood to the pectoralis major and pectoralis minor muscles, particularly their lateral portions.

• Pectoralis Major: This muscle is involved in movements such as adduction (bringing the arm closer to the body), internal rotation, and flexion of the shoulder. The lateral thoracic artery contributes to the blood supply of the lateral portion of this large muscle, supporting its function during arm and shoulder movements.
• Pectoralis Minor: The pectoralis minor is a smaller muscle located beneath the pectoralis major, and it helps stabilize the scapula by pulling it anteriorly and inferiorly. The lateral thoracic artery provides blood to the lateral portion of this muscle, ensuring its ability to stabilize the shoulder during movement.

Blood Supply to the Breast (in Females)

In females, the lateral thoracic artery plays an important role in the vascularization of the lateral portion of the breast.

• Nourishment of the Breast: The artery supplies oxygenated blood to the lateral aspect of the breast, contributing to the overall blood supply along with the internal thoracic artery and other smaller arteries. This blood flow is essential for the maintenance and function of the breast tissue, including the glandular and connective tissue.
• Support for Breast Development and Function: During periods of growth or physiological changes, such as puberty, pregnancy, or lactation, the blood supplied by the lateral thoracic artery helps nourish the developing breast tissue and supports the production of breast milk.
• Anastomoses with Other Arteries: The lateral thoracic artery forms anastomoses with the internal thoracic artery, which supplies the medial portion of the breast. These connections ensure a continuous blood flow to the entire breast, especially during periods of increased metabolic demand.

Blood Supply to the Axillary and Thoracic Skin

The lateral thoracic artery provides branches that supply blood to the skin and subcutaneous tissues of the lateral thoracic wall and axillary region.

• Nourishment of the Skin: The artery supplies the skin of the lateral chest wall and the axillary region, providing oxygen and nutrients necessary for maintaining the health and elasticity of the skin. This blood flow is critical for keeping the skin hydrated and ensuring proper wound healing in case of injury.
• Support for Cutaneous Function: The skin over the thoracic and axillary regions plays an important role in temperature regulation, sensation, and protection from external injuries. The blood supplied by the lateral thoracic artery helps maintain these essential skin functions by delivering nutrients and oxygen.

Blood Supply to the Axillary Lymph Nodes

The lateral thoracic artery provides small branches that contribute to the vascular supply of the axillary lymph nodes, which are located in the axilla (armpit region).

Lymph Node Nourishment: These lymph nodes are essential for the immune response and the drainage of lymphatic fluid from the upper limb, breast, and thoracic wall. The blood supplied by the lateral thoracic artery helps nourish the lymph nodes, ensuring that they function properly in filtering lymph and mounting an immune response to infections or foreign materials.

Support for Collateral Circulation

The lateral thoracic artery contributes to the collateral circulation in the lateral thoracic region. This network of vessels ensures that blood supply is maintained even if other nearby arteries are compromised.

Anastomoses with Other Arteries: The lateral thoracic artery forms anastomoses with other arteries in the axillary and thoracic regions, including the internal thoracic artery and thoracoacromial artery. These connections are important for maintaining continuous blood flow, especially during periods of increased demand, such as physical exertion or injury.

Oxygen and Nutrient Delivery

As with all arteries, the primary role of the lateral thoracic artery is to deliver oxygen and nutrients to the tissues it supplies.

• Muscle Function and Endurance: The oxygen and nutrients provided by the lateral thoracic artery are essential for maintaining the strength and endurance of the muscles it supplies, including the serratus anterior and pectoral muscles. Without proper blood flow, these muscles would fatigue quickly, leading to weakness or impaired movement.
• Tissue Repair and Maintenance: The lateral thoracic artery supports the maintenance and repair of the skin, muscles, and other tissues in the thoracic and axillary regions. Its blood supply is critical for healing after injury, surgery, or strain.

Clinical Significance

The lateral thoracic artery is clinically significant due to its role in supplying blood to key structures in the thoracic wall, axillary region, and, in females, the breast.

• Breast Surgery: The lateral thoracic artery plays a critical role in breast surgeries, including mastectomy and breast reconstruction procedures. Surgeons must be mindful of this artery to avoid excessive bleeding or compromised blood supply to the breast tissue. It also contributes to the vascular supply during flap-based reconstructions.
• Axillary Lymph Node Dissection: During procedures like axillary lymph node dissections for breast cancer, the lateral thoracic artery is important due to its proximity to the axillary lymph nodes. Care must be taken to avoid damaging this artery, which could result in hemorrhage or inadequate blood supply to surrounding tissues.
• Thoracic Trauma: In cases of thoracic or axillary trauma, injury to the lateral thoracic artery can lead to significant bleeding or compromise the blood flow to muscles like the serratus anterior, pectoralis major, and pectoralis minor, potentially affecting shoulder and arm movement.