The subclavian artery is a major artery that supplies blood to the arms, neck, thorax, and brain. There are two subclavian arteries, one on each side of the body: the
right subclavian artery arises from the
brachiocephalic trunk, while the
left subclavian artery originates directly from the
aortic arch.
Location
The subclavian artery is located deep in the upper thoracic region, running beneath the clavicle (collarbone). It arches laterally over the first rib, passing between the
anterior and
middle scalene muscles before descending into the axillary region to become the
axillary artery. Along its course, the subclavian artery gives rise to important branches, including the
vertebral artery,
internal thoracic artery, and
thyrocervical trunk, which supply the brain, chest wall, and upper limbs. The artery lies close to the brachial plexus, a network of nerves that innervates the upper limb.
Anatomy
The subclavian artery is a large vessel that supplies blood to the upper limbs, neck, and head, and it is divided into three parts based on its relationship to the
anterior scalene muscle. Each part gives rise to specific branches that supply various regions of the body. Below is a detailed description of the anatomy of the subclavian artery.
Origin
The origin of the subclavian artery differs between the right and left sides of the body:
- Right Subclavian Artery: The right subclavian artery originates from the brachiocephalic trunk, which is the first branch off the aortic arch. It arises posterior to the right sternoclavicular joint.
- Left Subclavian Artery: The left subclavian artery arises directly from the aortic arch, to the left of the trachea. Its origin is slightly more distal and posterior compared to the right subclavian artery.
Course and Segments
The subclavian artery is divided into three parts based on its location relative to the
anterior scalene muscle:
- First Part: The first part of the subclavian artery extends from its origin to the medial border of the anterior scalene muscle. This section lies deep to the sternocleidomastoid muscle and is positioned superior to the first rib. It gives rise to several major branches in this region, including the vertebral artery, internal thoracic artery, and thyrocervical trunk.
- Second Part: The second part of the subclavian artery lies posterior to the anterior scalene muscle, which separates it from the subclavian vein. In this segment, the artery lies more deeply in the neck and is closely related to the brachial plexus. It gives rise to the costocervical trunk.
- Third Part: The third part of the subclavian artery extends from the lateral border of the anterior scalene muscle to the outer border of the first rib, where it becomes the axillary artery. This section is relatively short and passes through the space between the clavicle and the first rib, known as the scalene triangle.
Relations
- Anteriorly: In the first part, the subclavian artery is covered by the sternocleidomastoid muscle and is crossed by the vagus nerve and phrenic nerve. It lies posterior to the subclavian vein and is separated from it by the anterior scalene muscle. The subclavius muscle and the clavicle are also positioned anterior to the artery.
- Posteriorly: The artery is closely related to the brachial plexus, especially in the second and third parts. The middle scalene muscle lies posterior to the artery as it passes between the scalene muscles.
- Medially: The artery is related medially to the trachea, esophagus, and thoracic duct on the left side.
- Laterally: The third part of the artery is related to the axillary artery and the structures of the upper limb.[7]
Branches
The subclavian artery gives rise to several key branches that supply blood to the brain, neck, chest wall, and upper limbs. These branches arise primarily from the first and second parts of the artery.
From the First Part:
- Vertebral Artery: This artery arises from the first part of the subclavian artery and ascends through the transverse foramina of the cervical vertebrae to supply the posterior part of the brain, including the brainstem and cerebellum.
- Internal Thoracic Artery: This artery descends along the inner aspect of the thoracic wall and supplies the anterior chest wall and diaphragm.[5]
- Thyrocervical Trunk: This is a short trunk that gives rise to the inferior thyroid artery, transverse cervical artery, and suprascapular artery, which supply the thyroid gland, neck muscles, and scapular region.
From the Second Part: 4.
Costocervical Trunk: The costocervical trunk arises from the second part of the subclavian artery and divides into the
deep cervical artery, which supplies the deep muscles of the neck, and the
supreme intercostal artery, which supplies the first two intercostal spaces.
From the Third Part: 5.
Dorsal Scapular Artery: In some individuals, the dorsal scapular artery arises from the third part of the subclavian artery. It supplies the rhomboid muscles and the medial border of the scapula. In other cases, it may originate from the thyrocervical trunk.
Termination
The subclavian artery terminates at the lateral border of the first rib, where it becomes the
axillary artery. The axillary artery supplies the upper limb and continues as the
brachial artery further down the arm.
Anastomoses
The subclavian artery forms several important anastomoses with other arteries:
- The vertebral artery anastomoses with the internal carotid system via the Circle of Willis, ensuring collateral circulation to the brain.
- The internal thoracic artery forms anastomoses with the intercostal arteries and superior epigastric artery.[3]
- The branches of the thyrocervical trunk anastomose with arteries supplying the scapular and neck regions, providing collateral circulation to the shoulder and neck.
Variations
Anatomical variations in the origin and course of the subclavian artery are relatively common. For example, the
right subclavian artery can arise directly from the aortic arch in cases where the brachiocephalic trunk is absent. The branches of the subclavian artery can also vary, with the
dorsal scapular artery sometimes arising from the thyrocervical trunk rather than the third part of the subclavian artery.
Function
The subclavian artery serves as the primary artery supplying oxygenated blood to the upper limbs, neck, thorax, and parts of the brain.
[1] Through its various branches, it ensures that critical regions receive the blood supply necessary for proper function. Below is a detailed explanation of its specific functions.
Blood Supply to the Upper Limb
One of the main functions of the subclavian artery is to provide blood to the
upper limb. As the artery continues beyond the lateral border of the first rib, it becomes the
axillary artery, which supplies the shoulder and arm with oxygenated blood. From the axillary artery, the blood flows into the
brachial artery to supply the forearm, wrist, and hand.
Axillary Artery: The transition of the subclavian artery into the axillary artery marks its major role in upper limb perfusion. The axillary artery and its branches nourish the muscles, bones, and connective tissues of the shoulder, arm, and hand.
Blood Supply to the Brain (via Vertebral Artery)
Another key function of the subclavian artery is to provide blood to the
posterior part of the brain, including the brainstem, cerebellum, and occipital lobes, through its branch, the
vertebral artery.
Vertebral Artery: The vertebral artery is a major branch of the subclavian artery. It ascends through the transverse foramina of the cervical vertebrae and enters the cranial cavity through the foramen magnum. The vertebral arteries from both sides merge to form the
basilar artery, which supplies the posterior circulation of the brain, including the brainstem and cerebellum. The vertebral artery's contribution to the
Circle of Willis also ensures collateral circulation, providing an alternative route for blood to reach the brain if other pathways are compromised.
Blood Supply to the Thoracic Wall and Diaphragm (via Internal Thoracic Artery)
The subclavian artery provides blood to the
anterior thoracic wall and the
diaphragm through the
internal thoracic artery, which descends along the inner surface of the thoracic wall.
[8]
Internal Thoracic Artery: This artery supplies the intercostal muscles, sternum, and thoracic wall. It also gives off branches, such as the
anterior intercostal arteries, which provide blood to the muscles and skin of the chest. Additionally, the internal thoracic artery continues downward to supply the diaphragm through its branches, the
musculophrenic artery and
superior epigastric artery. These arteries are essential for supporting the diaphragm’s function in respiration.
Blood Supply to the Neck and Thyroid Gland (via Thyrocervical Trunk)
The subclavian artery supplies blood to the
neck,
thyroid gland, and
scapular region via the
thyrocervical trunk.
Thyrocervical Trunk: This trunk gives rise to several arteries that supply the neck and thyroid gland. The
inferior thyroid artery is a major branch of the thyrocervical trunk, which supplies the thyroid gland and the parathyroid glands.
[6] The
transverse cervical artery and
suprascapular artery are other branches that supply muscles in the neck and upper back, including the trapezius and the muscles around the scapula.
Blood Supply to the Deep Neck and Upper Intercostal Spaces (via Costocervical Trunk)
The subclavian artery, through its
costocervical trunk, provides blood to the deep structures of the neck and the upper intercostal spaces.
Costocervical Trunk: The costocervical trunk arises from the second part of the subclavian artery and branches into the
deep cervical artery, which supplies the deep muscles of the neck, and the
supreme intercostal artery, which provides blood to the first two intercostal spaces. These arteries ensure that the neck muscles and upper chest receive an adequate blood supply, supporting activities such as breathing, posture, and movement.
Blood Supply to the Scapular Region (via Dorsal Scapular Artery)
In some individuals, the subclavian artery gives rise to the
dorsal scapular artery, which supplies blood to the
scapular region.
[4]
Dorsal Scapular Artery: This artery supplies the
rhomboid muscles and the
levator scapulae. It travels along the medial border of the scapula and helps form anastomoses with other arteries in the shoulder and back, such as the suprascapular artery and circumflex scapular artery. This blood supply is critical for maintaining the function and strength of the muscles that move and stabilize the shoulder blade.
Contribution to Collateral Circulation
The subclavian artery plays a significant role in
collateral circulation by forming important anastomoses between its branches and other arteries, ensuring that blood flow can be rerouted in the event of blockages or arterial damage.
- Vertebral Artery and Circle of Willis: The vertebral artery, as part of the Circle of Willis, ensures collateral circulation to the brain, allowing blood to flow between the anterior and posterior circulations of the brain. This is crucial in preventing ischemic events in the brain.
- Scapular Anastomoses: The dorsal scapular artery and suprascapular artery form part of the scapular anastomotic network, providing collateral blood flow to the shoulder and upper back.
Support for Thoracic and Abdominal Structures
Through its branches, such as the
internal thoracic artery and
superior epigastric artery, the subclavian artery ensures blood supply to thoracic and upper abdominal structures.
Anterior Thoracic Wall and Diaphragm: The internal thoracic artery and its branches, the musculophrenic and superior epigastric arteries, supply the anterior thoracic wall and diaphragm.
[2] This is important for breathing, chest wall movement, and overall thoracic stability.
Clinical Significance
The subclavian artery is of great clinical significance because it supplies blood to the upper limbs, neck, brain, and parts of the thoracic region. Its branches, such as the
vertebral artery and
internal thoracic artery, are crucial for providing oxygenated blood to the brain and chest. Any obstruction, injury, or disease affecting the subclavian artery can have severe consequences, such as
subclavian steal syndrome, where blood flow is redirected from the brain to the arm due to a blockage. This can cause symptoms like dizziness, visual disturbances, and arm weakness.
The subclavian artery is also involved in conditions such as
thoracic outlet syndrome, where compression of the artery between the scalene muscles and first rib results in reduced blood flow to the arm. It is important in surgical procedures, including
coronary artery bypass grafting (CABG), where the
internal thoracic artery (a branch of the subclavian) is often used to bypass blocked coronary arteries. Understanding its anatomy is vital for interventions in trauma, vascular surgeries, and diagnosis of vascular disorders.