Blood supply and innervation only deltoid and scapula region

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Here is a comprehensive breakdown of the blood supply and innervation of the deltoid and posterior scapular region, sourced from Gray's Anatomy for Students and the THIEME Atlas of Anatomy.

DELTOID REGION

Innervation

Axillary nerve (C5, C6) — branch of the posterior cord of the brachial plexus
- Exits the axilla through the quadrangular space, passing posteriorly around the surgical neck of the humerus
- Innervates the deltoid (all three parts) and the teres minor
- Gives off the superior lateral cutaneous nerve of the arm — carries sensation from skin over the inferior part of the deltoid

Blood Supply

Posterior circumflex humeral artery — arises from the 3rd part of the axillary artery
- Travels with the axillary nerve through the quadrangular space
- Supplies the deltoid, related muscles, and the glenohumeral joint
Anterior circumflex humeral artery — also from the 3rd part of the axillary artery; smaller contribution, anastomoses around the surgical neck

Fig. 7.36 — Neurovascular supply of the deltoid (posterior view):

Neurovascular supply of trapezius and deltoid, posterior view

POSTERIOR SCAPULAR REGION

This region lies deep to the trapezius and deltoid, containing the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, teres major) and the long head of triceps.

Nerves

1. Suprascapular Nerve (C5, C6)

Originates from the superior trunk of the brachial plexus
Passes through the suprascapular foramen (beneath the superior transverse scapular ligament)
Innervates supraspinatus, then passes through the greater scapular (spinoglenoid) notch to innervate infraspinatus
No cutaneous branches

2. Axillary Nerve (C5, C6)

Enters the posterior scapular region via the quadrangular space
Innervates deltoid and teres minor
Cutaneous branch: superior lateral cutaneous nerve of the arm (skin over inferior deltoid)

Other muscles in the region (for completeness):

Teres major → Inferior subscapular nerve (C6, C7)

Rhomboids → Dorsal scapular nerve

Levator scapulae → Dorsal scapular nerve + C3, C4 directly

Long head of triceps → Radial nerve (C6–C8) — passes via triangular interval

Blood Supply — Three Major Arteries

1. Suprascapular Artery

Branch of the thyrocervical trunk (from subclavian artery), occasionally directly from the 3rd part of subclavian
Enters the posterior scapular region superior to the suprascapular foramen (the nerve goes through the foramen; the artery goes over the ligament — mnemonic: "Army goes under the bridge, Navy goes over")
Supplies supraspinatus, infraspinatus, and multiple structures along its course

2. Posterior Circumflex Humeral Artery

Branch of the 3rd part of the axillary artery
Passes through the quadrangular space with the axillary nerve
Supplies deltoid, teres minor, glenohumeral joint

3. Circumflex Scapular Artery

Branch of the subscapular artery (which itself branches from the 3rd part of the axillary artery)
Leaves the axilla through the triangular space
Passes through the origin of teres minor
Forms an anastomotic network around the scapula with the suprascapular and posterior circumflex humeral arteries

Veins follow the named arteries and connect with vessels in the neck, back, arm, and axilla.

Fig. 7.38 — Nerves and arteries of the posterior scapular region (posterior view):

Nerves and arteries of the posterior scapular region — axillary nerve, suprascapular nerve, posterior circumflex humeral artery, circumflex scapular artery

Fig. 7.39 — Scapular arterial anastomotic network:

Scapular arterial anastomosis — suprascapular, circumflex scapular, posterior circumflex humeral arteries from thyrocervical trunk and axillary artery

Key Gateways (Spaces) Summary

Space	Boundaries	Contents
Suprascapular foramen	Suprascapular notch + superior transverse ligament	Suprascapular nerve (through); suprascapular artery (over ligament)
Quadrangular space	Teres minor (sup), teres major (inf), long head of triceps (med), surgical neck of humerus (lat)	Axillary nerve + posterior circumflex humeral artery
Triangular space	Teres minor (sup), teres major (inf), long head of triceps (lat)	Circumflex scapular artery
Triangular interval	Teres major (sup), long head of triceps (med), humerus (lat)	Radial nerve + profunda brachii artery

Clinical note — Quadrangular Space Syndrome: Hypertrophy or fibrosis of the quadrangular space muscles can compress the axillary nerve, causing teres minor atrophy and weakness/altered deltoid function.

— Gray's Anatomy for Students, pp. 834–840

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