Simplifying the Anatomy of the upper limb: Arterial Supply of the shoulder Region

Introduction

As we go about our daily lives, we often don't think about thebnetwork of blood vessels that keep our bodies functioning properly. However, when it comes to the axillary region, understanding the anatomy of the arterial supply is crucial. The axillary region is a complex area of the body located beneath the shoulder joint, and it plays a vital role in the movement and function of our arms.

In this essay, we will explore the anatomy of the arterial supply of the axillary region. By delving into this topic, we can gain a better understanding of how blood flows through this area, supplying oxygen and nutrients to the surrounding tissues. So, let's take a closer look at the arteries that make up the arterial supply of the axillary region and the important role they play in keeping our bodies healthy and functioning properly.

Subclavian Artery

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The course of the subclavian artery from its origin to the point where it transitions into the axillary artery is a critical pathway that involves several key anatomical landmarks and structures. Let's explore this journey in detail:

Origin: The subclavian artery originates on the right side of the body from the brachiocephalic trunk, the first branch of the aortic arch. On the left side, the subclavian artery stems directly from the aortic arch. It ascends superiorly and laterally, passing behind the sternoclavicular joint.

First Part (Proximal): The first part of the subclavian artery extends from its origin to the medial border of the scalenus anterior muscle. This segment is relatively short and is located deep in the neck, running posterior to the sternoclavicular joint. It gives off important branches such as the vertebral artery, internal thoracic artery, and thyrocervical trunk.

Second Part (Medial): The second part of the subclavian artery is situated between the anterior and middle scalene muscles. It runs posterior to the scalenus anterior muscle and is relatively fixed in its position. Branches originating from this segment include the costocervical trunk and the dorsal scapular artery.

Third Part (Distal): The third part of the subclavian artery extends from the lateral border of the scalenus anterior muscle to the outer border of the first rib. At this point, the subclavian artery transitions into the axillary artery. This segment gives off branches like the subscapular artery, which further divides into the circumflex scapular artery and thoracodorsal artery, as well as the anterior and posterior humeral circumflex arteries.

Passage under the Clavicle: As the subclavian artery transitions into the axillary artery, it passes beneath the clavicle. This passage under the clavicle exposes the artery to potential compression and other mechanical stresses, especially in cases of trauma or repetitive movements of the shoulder joint.

Relation to Brachial Plexus: Throughout its course, the subclavian artery is closely related to the brachial plexus, which is a network of nerves that innervate the upper extremities. The roots of the brachial plexus lie in close proximity to the subclavian artery in the neck, and variations in the course of the artery can impact the surrounding nerve structures.

Collateral Circulation

The subclavian artery provides a pathway for collateral circulation, especially in cases where there is occlusion or stenosis of other major arteries in the upper extremities. The collateral circulation via branches of the subclavian artery helps maintain blood flow to the arm even when there are blockages in other arteries.

Clinical Relevance
The knowledge course of the subclavian artery is important for healthcare professionals in diagnosing and treating various conditions affecting the upper extremities. In conditions such as thoracic outlet syndrome or subclavian steal syndrome, where there is compression or occlusion of the subclavian artery, knowledge of the artery's course is essential for proper management.

The Axillary artery

The axillary artery is a crucial blood vessel located in the upper extremity, serving as a major conduit for blood flow from the subclavian artery to the brachial artery.

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Origin and Course

The axillary artery begins at the lateral border of the first rib as a continuation of the subclavian artery. It extends to the lower border of the teres major muscle, where it transitions into the brachial artery. The axillary artery runs through the axilla or armpit region, giving off several branches along its course.

Segments

The axillary artery can be divided into three segments based on its relationship to the pectoralis minor muscle:

• First (proximal) part: Superior to the pectoralis minor muscle, it gives off branches like the superior thoracic artery.
• Second (deep) part: Posterior to the pectoralis minor muscle, it gives rise to the thoracoacromial artery, lateral thoracic artery, and subscapular artery.
• Third (distal) part: Lateral to the pectoralis minor muscle, it continues as the brachial artery and gives off branches like the circumflex humeral arteries.

Branches

• Superior Thoracic Artery: Arises from the first part of the axillary artery and supplies the first and second intercostal spaces.
• Thoracoacromial Artery: Divides into branches that supply the deltoid, acromial, clavicular, and pectoral regions.
• Lateral Thoracic Artery: Runs along the lateral border of the pectoralis minor muscle, supplying the serratus anterior muscle and nearby tissues.
• Subscapular Artery: Largest branch of the axillary artery, it divides into the circumflex scapular artery and thoracodorsal artery that supply the scapula and surrounding structures.

Relationships

• Veins: The axillary vein accompanies the axillary artery, forming the axillary sheath together. The close proximity of these structures allows for easy access for vascular procedures and catheterizations.
• Nerves: The axillary artery and its branches are closely associated with the brachial plexus, a network of nerves that innervate the shoulder and upper extremity. Understanding the neurovascular relationships in this region is essential for surgical and diagnostic procedures.
• Muscles: The axillary artery runs deep to various muscles in the shoulder region, including the deltoid, teres major, and pectoralis major, highlighting its importance in supplying oxygenated blood to these muscles.

Clinical Significance

Pulse Examination: The axillary artery pulse is an important clinical indicator used to assess blood flow in the upper extremity.
Thoracic Outlet Syndrome: Compression of the axillary artery, often in the context of thoracic outlet syndrome, can lead to symptoms like arm pain, numbness, and weakness.
Arterial Injuries: Trauma to the axillary artery can result in significant bleeding and compromise blood flow to the arm, requiring prompt medical intervention.
Vascular Access: The axillary artery can serve as a site for arterial catheterization, especially in cases where radial or brachial access is not feasible.

In conclusion, the axillary artery is a critical vascular structure in the upper extremity, playing a key role in supplying oxygenated blood to the shoulder, arm, and surrounding tissues. Its branching pattern, relationships with adjacent structures, and clinical relevance make it an essential component of the circulatory system. Understanding the anatomy and function of the axillary artery is paramount for healthcare providers involved in the evaluation and treatment of vascular disorders affecting the upper limb.

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Please consult your Atlas textbooks while reading this topic for easy and fast understanding

References

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(5) Arterial Supply to the Upper Limb - Subclavian - TeachMeAnatomy. https://teachmeanatomy.info/upper-limb/vessels/arteries/.
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