CorpusHuman Anatomy
SkeletalBone

Scapula

Scapula

Also known as: shoulder blade, acromion, coracoid process, glenoid cavity

A flat, triangular bone on the posterolateral chest wall (ribs 2–7) that forms the posterior pectoral girdle, the socket of the shoulder joint and the attachment for 17 muscles.

Show on body map Muscles — Posterior View

Overview

The scapula has three borders (superior, medial/vertebral and lateral/axillary), three angles (superior at T2, inferior at T7, and lateral bearing the glenoid) and two surfaces. The concave costal (anterior) surface forms the subscapular fossa (subscapularis). The posterior surface is divided by the spine into a small supraspinous fossa (supraspinatus) and a larger infraspinous fossa (infraspinatus). The spine continues laterally as the flat acromion, which forms the point of the shoulder and articulates with the clavicle.

The glenoid cavity — a shallow, pear-shaped fossa deepened by the glenoid labrum — articulates with the humeral head; above and below it lie the supraglenoid tubercle (long head of biceps) and infraglenoid tubercle (long head of triceps). The hook-like coracoid process projects anteriorly from the upper border and anchors pectoralis minor, coracobrachialis, the short head of biceps and the coracoclavicular, coracoacromial and coracohumeral ligaments. Medial to the coracoid, the suprascapular notch is bridged by the superior transverse scapular ligament: the suprascapular nerve passes below and the artery above.

The scapula glides on the thoracic wall (the scapulothoracic "joint"), contributing about one-third of arm elevation (scapulohumeral rhythm ≈2:1 glenohumeral to scapular movement).

Location

Posterolateral thoracic wall, overlying ribs 2–7.

Parts & subdivisions

  1. Glenoid cavity
    Shallow socket for the humeral head; deepened by the labrum.
  2. Acromion
    Lateral continuation of the spine; forms the roof of the shoulder.
  3. Coracoid process
    Anterior hook; pectoralis minor, coracobrachialis, short head of biceps.
  4. Spine
    Posterior ridge; trapezius and deltoid attach.
  5. Supraspinous and infraspinous fossae
    Origins of supraspinatus and infraspinatus (rotator cuff).
  6. Subscapular fossa
    Origin of subscapularis.
  7. Supraglenoid and infraglenoid tubercles
    Long heads of biceps and triceps respectively.
  8. Suprascapular notch
    Suprascapular nerve beneath the transverse scapular ligament, artery above.
  9. Inferior angle
    Overlies the 7th rib/T7; landmark for counting ribs posteriorly.

Anatomy

Arterial supply

Suprascapular, dorsal scapular and circumflex scapular arteries — the scapular anastomosis, a collateral route between the subclavian and axillary arteries.

Articulations

Humerus (glenohumeral joint), clavicle (acromioclavicular joint); scapulothoracic gliding articulation (functional, not anatomical).

Ligaments

Coracoclavicular, coracoacromial (forms the coracoacromial arch), coracohumeral, glenohumeral, superior and inferior transverse scapular ligaments.

Ossification

Primary centre in the body ≈week 8; coracoid centre ≈1st year (fuses ≈15 years); several secondary centres at puberty (acromion, inferior angle, medial border, glenoid) fuse by ≈20–25 years. Unfused acromial centre = os acromiale (≈8%).

Function

  • Forms the socket of the shoulder joint
  • Provides a mobile base that orients the glenoid for arm movement
  • Attachment for the rotator cuff, deltoid, trapezius, serratus anterior, rhomboids, levator scapulae and others (17 muscles)

Clinical significance

Winged scapula

Damage to the long thoracic nerve (C5–C7; e.g. axillary surgery, carrying heavy loads) paralyses serratus anterior: the medial border lifts off the chest wall when pushing against a wall, and abduction above 90° is weak.

Scapular fracture

Uncommon because of thick muscle cover; implies high-energy trauma and associated chest injuries.

Mnemonics

Suprascapular notch

"Army over the bridge, Navy under the bridge": suprascapular artery passes above the transverse scapular ligament, the nerve below.

Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.