Understanding the Subclavian Artery

The human body is a marvel of intricate design, and nowhere is this more evident than in the cardiovascular system. The subclavian artery, a vital blood vessel in the upper torso, plays a crucial role in delivering oxygenated blood to various parts of the body. In this article, we will embark on a journey through the subclavian artery, exploring its anatomy, branches, and functions. So, let's dive in!

A Quick Overview

Before we delve into the depths of the subclavian artery, let's start with a brief overview of its origins and connections. The subclavian artery arises directly from the aorta on the left side, while on the right side, it branches off from the brachiocephalic trunk. This distinction arises from the fact that the aorta curves to the left before descending, eliminating the need for additional length provided by the brachiocephalic trunk. It is important to note that although we will primarily focus on the right subclavian artery, most of the information discussed applies to the left subclavian artery as well, with the only significant difference being the length of the left artery, which is approximately four centimeters longer.

Divisions and Landmarks

As the subclavian artery progresses, it runs beneath the clavicle and over the first rib. This portion of its course is commonly referred to as the "first part." From a topographical perspective, we divide the subclavian artery into three parts, using the anterior scalene muscle as a landmark. The first part extends from the origin to the medial border of the anterior scalene muscle. The second part lies behind the anterior scalene muscle, and finally, the third part spans from the lateral border of the anterior scalene muscle to the outer border of the first rib, where it transitions into the axillary artery.

Exploring the Branches: VITCD - Vitamin CD

To better understand the branches of the subclavian artery, let's employ a mnemonic: VITZ, or "Vitamin CD." Each letter represents a different set of branches associated with specific topographical parts of the artery.

Summarising the Origin and Branches of The Upper Limbs. Source: Wikimedia Commons

V - Vertebral Artery

The vertebral artery ascends through the neck, passing through the transverse foramina of the cervical vertebrae (C1 to C7). Upon exiting the transverse foramen of C1, it traverses the foramen magnum and enters the posterior cranial fossa. Here, it joins the vertebral artery of the opposite side, forming the basilar artery. The basilar artery is located behind the fossa turcica and contributes to the formation of the Circle of Willis through the posterior cerebral arteries. The vertebral artery has three parts: the pre-vertebral part, the transverse part with its side branches, and the intracranial part.

• The pre-vertebral part does not give rise to any branches.
• The transverse part has two side branches:
  • Muscular branches, which supply the deep muscles of the neck, including the longest colli, the longest capitis, and the rectus capitis muscles.
  • Spinal branches, which traverse the intervertebral foramina and provide blood supply to the upper cervical segments (C5-C6).
• The intracranial part of the vertebral artery gives rise to the following branches:
  • Anterior spinal artery and posterior spinal arteries, which supply the spinal cord.
  • Inferior posterior cerebellar artery, which nourishes the inferior surface of the cerebellum.
  • Meningeal branch, supplying the meninges of the posterior cranium.

I - Internal Thoracic Artery

The internal thoracic artery descends along the anterior wall of the thoracic cavity. Upon reaching the seventh rib, it divides into two terminal branches: the superior epigastric artery and the muscular phrenic artery. Additionally, the internal thoracic artery gives rise to several side branches, which we can remember using the mnemonic "BPMS" (Beats Per Minute).

• P - Pericardial Phrenic: Supplies the pericardium, diaphragm, and mediastinal structures.
• A - Anterior Intercostal Arteries: Provides blood supply to the upper five or six intercostal spaces, connecting with the posterior intercostal arteries of the thoracic aorta.
• S - Sternal: Supplies the sternum.
• T - Timeik: Nourishes the timeik muscle.
• B - Bronchial: Supplies the lower part of the bronchial tree.
• P - Perforating: Feeds the mammary glands.
• M - Mediastinal: Supplies the mediastinal structures.

T - Thyrocervical Trunk

The thyrocervical trunk is a short arterial trunk that arises in close proximity to the first rib. It further divides into four arteries:

• Inferior Thyroid Artery: Ascends and terminates at the thyroid gland, supplying structures such as the larynx, trachea, pharynx, and esophagus in its vicinity.
• Ascending Cervical Artery: Shares similar side branches with the transverse part of the vertebral artery, providing blood supply to the deep and lateral neck muscles.
• Transverse Cervical Artery: Extends to the superior angle of the scapula and subsequently divides into the superficial cervical artery, which supplies the superficial muscles like the trapezius and levator scapulae, and the dorsal scapular artery, which descends along the medial margin of the scapula and nourishes muscles such as the rhomboids.
• Suprascapular Artery: Courses towards the scapula, providing blood supply to the supraspinous and infraspinous regions. It communicates with the circumflex scapular artery, a branch of the axillary artery.

C - Costo Cervical Trunk

Costo Cervical Trunk, a small trunk originating from the second part of the subclavian artery. It branches into two arteries, each with its own distinct role and significance. Let's explore them further.

1. Deep Cervical Artery: This artery journeys into the depths of the neck, supplying the intricate structures within. It also gives rise to branches that provide nourishment to the spinal cord, ensuring its optimal functioning.
2. Supreme Intercostal Artery: Descending gracefully, this artery divides into posterior intercostal arteries, which intricately supply the muscles of the first and second intercostal spaces. These arteries play a crucial role in maintaining the strength and functionality of these muscles.

The Costo Cervical Trunk, with its branches, contributes significantly to the overall blood supply within the neck and thoracic region, supporting the vital structures and promoting their harmonious function.

D - Dorsal Scapular Artery

The dorsal scapular artery is of particular interest as it demonstrates variations in its origin. In some individuals, it branches off from the transverse cervical artery, as mentioned earlier. However, in others, it arises directly from the subclavian artery itself, along the lateral border of the anterior scalene muscle.

Conclusion

The subclavian artery is a remarkable vessel, intricately connected to various structures and organs of the upper torso. By understanding its branches and their functions, we gain valuable insights into the blood supply of the neck, brain, spinal cord, thoracic wall, and upper limb. Hopefully, this article has provided a comprehensive overview of the subclavian artery, shedding light on its anatomy and enlightening the mnemonic "VITCD - Vitamin CD" for easy recall. 

Author Footnotes

Applied Anatomy - Subclavian Steal Syndrome: In this syndrome, there is a significant blockage or narrowing of the subclavian artery, usually on one side, that leads to reduced blood flow to the affected arm.

The term "steal" refers to the redirected blood flow that occurs in this condition. When there is a blockage in the subclavian artery, blood may flow in the reverse direction from the vertebral artery, which is another artery that branches off from the subclavian artery. This reversed blood flow is referred to as "stealing" blood from the brain, as it diverts blood away from its normal path to supply the arm.

Subclavian Steal Syndrome. Source: Wikimedia Commons

The reversal of blood flow in the vertebral artery can lead to a decrease in blood supply to the brain, which may cause symptoms such as dizziness, lightheadedness, and even fainting in some cases. However, many individuals with subclavian steal syndrome may not experience any symptoms.

Most Common Cause: Atherosclerosis

References:

1. Tubbs, R. S., Shoja, M. M., & Loukas, M. (2021). Subclavian Artery. In StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK546678/
2. Stone, T. A., & Shuman, B. R. (2021). Anatomy, Shoulder and Upper Limb, Subclavian Artery. In StatPearls [Internet]. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532911/
3. Singh, S., & Tiwari, S. (2022). Subclavian Artery Anatomy. In Treasure Island (FL): StatPearls Publishing.