Common ways the question is asked

• "Describe the arterial anastomosis around the scapula."
• "Name the arteries taking part in the anastomosis around the scapula."
• "Draw a labeled diagram of the scapular anastomosis."

• "What is the clinical importance of the anastomosis around the scapula?"
• "If the subclavian artery is ligated proximal to the thyrocervical trunk, how is the limb supplied with blood?"
• "How is collateral circulation established after ligation/occlusion of the third part of the axillary artery?"
• "A patient needs axillary artery ligation for trauma/aneurysm - which anastomosis maintains blood flow to the upper limb, and why is ligation only safe distal to the subscapular artery?"

• "Enumerate the arteries participating in the scapular arcade."
• "Which artery connects the thyrocervical trunk system to the axillary artery system around the scapula?"

• Given a diagram of the scapula with arteries labeled, "identify the vessels forming the anastomosis" or "trace the anastomotic pathway."

The core answer you need for all these variants

• Suprascapular artery - branch of the thyrocervical trunk (from subclavian artery). Passes over the superior transverse ligament of the scapula into the supraspinous fossa, runs past the neck of the scapula under the (often absent) inferior transverse ligament, and enters the infraspinous fossa.
• Deep branch (dorsal scapular artery) of the transverse cervical artery - also from the thyrocervical trunk (or directly from subclavian artery in some individuals). Descends along the medial border of the scapula.
• Circumflex scapular artery - branch of the subscapular artery, which itself arises from the third part of the axillary artery. It passes through the triangular space (between teres major and teres minor) to reach the infraspinous fossa.

How this topic is typically asked

• "Describe the anastomosis over/around the acromion process."
• "Name the arteries that form the acromial anastomosis (rete acromiale)."

• "Why is the acromial anastomosis surgically important?"
• "Which vessel is at risk during resection of the coracoacromial ligament or during shoulder arthroscopy/rotator cuff surgery?"
• "What is the clinical significance of the acromial branch of the thoracoacromial artery in the deltopectoral or deltoid-splitting approach to the shoulder?"

• "Enumerate the contributors to the arterial network near the acromion."

The core answer

• Acromial branch of the thoracoacromial artery - the thoracoacromial artery arises as a short trunk from the axillary artery (deep to pectoralis minor) and divides into acromial, clavicular, deltoid, and pectoral branches; the acromial branch spreads out "in all directions" to help form this network near the acromion (Color Atlas of Human Anatomy Vol. 2, p. 105-106; THIEME Atlas of Anatomy, Branches of the axillary artery).
• Acromial branch of the suprascapular artery - the suprascapular artery (from the thyrocervical trunk of the subclavian artery) gives an acromial branch that pierces the trapezius/crosses the acromion to join this network (Gray's Anatomy for Students, Trapezius blood supply).
• A contribution from the posterior circumflex humeral artery (branch of the third part of the axillary artery) is classically described as the third participant in most standard anatomy teaching, completing the network around the acromion and greater tubercle region.

• The acromial branch of the thoracoacromial (coracoacromial) artery runs on the medial aspect of the coracoacromial ligament and lies within it - surgeons must identify and often cauterize/ligate it during arthroscopic subacromial decompression or resection of the coracoacromial ligament, since it is easily transected during these procedures (Campbell's Operative Orthopaedics 15th ed.; Miller's Review of Orthopaedics 9th ed.).
• Like the scapular arcade, this network helps maintain collateral blood flow to the shoulder region and is a landmark orthopedic surgeons watch for to avoid bleeding complications during shoulder surgery.

Origin and Insertion

• Origin: Upper two-thirds of a flattened strip of bone on the posterior surface of the scapula, immediately adjacent to the lateral border of the scapula
• Insertion: Inferior facet on the posterior surface of the greater tubercle of the humerus
• Innervation: Axillary nerve (C5, C6)
• Action: Lateral (external) rotation of the arm at the glenohumeral joint; stabilizes the joint (it's a rotator cuff muscle)

• Origin: Elongated oval area on the posterior surface of the inferior angle of the scapula
• Insertion: Medial lip of the intertubercular (bicipital) sulcus on the anterior surface of the humerus
• Innervation: Lower (inferior) subscapular nerve (C6, C7)
• Action: Medial (internal) rotation and extension of the arm at the glenohumeral joint; stabilizes the joint

• Origin: Infraglenoid tubercle of the scapula (just below the glenoid cavity)
• Insertion: Joins the common triceps tendon (with the medial and lateral heads) onto the olecranon process of the ulna
• Innervation: Radial nerve (C6, C7, C8)
• Action: Extends the forearm at the elbow; as it crosses the shoulder, it also assists in extension and adduction of the arm at the glenohumeral joint