Scapula

Posterior View

Shoulder girdle & thoracic cage

Definition: scapula is a flat bone that connects the trunk to the upper limb. It is the posterior bone of shoulder girdle. It is also known as shoulder blade.

Shape: triangular in outline.

Site: lies on the postero-lateral aspect of the chest wall extending from the 2nd to 7th rib.

Side determination:

1. Glenoid cavity: is directed laterally & upwards.
2. Spine is directed backwards.
3. Subscapular fossa: is directed fowards.

Posterior, anterior & lateral sides of scapula

General features: It is consist of 2 surfaces, 3 angles, 3 borders, 3 processes

• Surfaces:

Costal (anterior) surface	Dorsal (posterior) surface
- It is directed forwards & medially - Facing the ribs - It carries subscapular fossa	- It is directed backwards & laterally - Palpated from back - Spinous process, divides it into two fossae: infraspinous fossa & supraspinous fossa

• Angles:

Superior angle	Lateral angle (head)	Inferior angle (apex)
- Thin, smooth & rounded - Right angle - Between superior & medial borders - Opposite the 2nd rib	- Thickest part of the bone - Glenoid cavity - Articulate with head of humerus - Supra & infraglenoid tubercles	- Thick & rough - Acute angle - Between medial & lateral borders - Opposite the 7th rib

• Borders:

Superior border	Lateral (axillary) border	Medial (vertebral) border
- Thinnest & shortest - Extend from the superior angle to coracoids process - Near the root of coracoids process, there is suprascapular notch	- Thickest - Extend from the glenoid cavity to the inferior angle - At the upper end, there is infraglenoid tubercle	- Average thickness & longest - Extend from the superior angle to the inferior angle - Presents anterior lip, posterior lip & an intermediate narrow area

• Processes:

Spinous process	Acromion process	Coracoid process
- A triangular plate of bone - Divides the dorsal surface into 2 fossae - It has 2 ends: §  Lateral end- continuous with acromion process §  Medial end- forms the root of the spine - It has 2 surfaces: §  Upper surface §  Lower surface - It has 3 borders: §  Anterior border- attached to scapula §  Posterior border- free, subcutaneous (crest of spine), has upper &lower lips §  Lateral border- free, bounds the spinoglenoid notch	- A projecting forwards from the lateral end of the spine making right angle - It has 2 surfaces: §  Upper surface §  Lower surface - It has 2 borders: §  Medial border- continuous with upper lip of crest of spine, carries small articular facet for articulation with clavicle (acromioclavicular joint) §  Lateral border- continuous with lower lip of the crest of spine at the acromial angle	- A projection from the upper border of the head (glenoid cavity - Directed fowards & slightly laterally - Root of process is related medially to the supraglenoid tubercle & laterally to the suprascapular notch - It has 2 surfaces: §  Upper surface- carries a rough area for muscle attachment §  Lower surface - It has 2 borders: §  Medial border §  Lateral border

Anterior surface of scapula (click at the image to enlarge)

Posterior surface of scapula (click at the image to enlarge)

Lateral border of scapula (click at the image to enlarge)