SCAPULA ANATOMY

GENERAL CHARACTERISTICS

• Large, flat, triangular bone forming part of the shoulder girdle
• Features two surfaces, three processes, three borders, and three angles
• The lateral angle houses the glenoid cavity, which articulates with the head of the humerus
• The costal surface faces the ribs, while the posterior surface features a prominent spinal ridge
• The acromion extends from the spine, protruding sideways, bending forward and upward

COSTAL SURFACE OF THE SCAPULA

• Front surface facing the ribs
• Accommodates and provides attachment for the Subscapularis muscle

Subscapular Fossa

• Large, concave depression located on the costal (anterior) side
• Structure:
  • Marked by oblique ridges
  • Medial two-thirds: Ridged, providing attachment for the Subscapularis muscle
  • Lateral one-third: Smooth, in contact with the muscle

POSTERIOR SURFACE OF THE SCAPULA (DORSAL SURFACE)

• The posterior surface is arched and divided by the spine into two regions
• Supraspinous fossa above and infraspinous fossa below
• Key features include the deltoid tubercle, spinoglenoid notch, and multiple muscle attachment points

Spine of the Scapula

• Structure:
  • Prominent, triangular plate running obliquely across the dorsal surface
  • Divides scapula into supraspinous and infraspinous fossae
• Lateral End:
  • Elevates and forms the acromion

Deltoid Tubercle

• Location: Medial portion of the superior lip of the posterior border of the spine
• Function: Attachment point for the lower Trapezius and Deltoideus muscles

Spinoglenoid Notch

• Location: Lateral border or base of the spine
• Function: Passageway between the supraspinous and infraspinous fossae

Supraspinous Fossa

• Location: Above the spine on the dorsal surface
• Features: Smooth and concave
• Function: Gives origin to the Supraspinatus muscle

Infraspinous Fossa

• Location: Below the spine on the dorsal surface
• Features: Larger and more extensive than the supraspinous fossa
• Function: Gives origin to the Infraspinatus muscle

BORDERS OF THE SCAPULA

Medial (Vertebral) Border

• Features:
  • Longest edge, extending from medial to inferior angle
  • Above the spine forms an obtuse angle with the portion below
• Function: Provides insertion for various muscles

Superior Border

• Features:
  • Shortest and thinnest of the three borders
  • Concave, extending from medial angle to base of the coracoid process
  • Includes the scapular notch at its lateral part
• Scapular Notch:
  • Located along the superior border
  • Partly formed by the base of the coracoid process
  • Becomes a foramen when bridged by a ligament for nerve passage

Lateral (Axillary) Border

• Features:
  • Thickest part of the bone
  • Runs from lower margin of the glenoid cavity to the inferior angle
• Function: Provides origin for muscles

Lateral Features of the Scapula

Glenoid Cavity (Glenoid Process)

• Location: At the lateral angle
• Features:
  • Shallow cavity, wider at the bottom
  • Rimmed by fibrocartilage (glenoid labrum) for joint stabilization
• Function: Articulates with the arm bone, forming the shoulder joint

Coracoid Process

• Features:
  • Hook-like projection, starts broad and curves up and forward
  • Located above the glenoid cavity
• Function: Attachment point for various muscles and ligaments

Supraglenoid Tubercle

• Location: Apex of the glenoid cavity
• Function: Origin point for the long head of the Biceps brachii muscle

Infraglenoid Tubercle

• Location: Below the glenoid cavity, measures about 2.5 cm in length
• Function: Origin point for the long head of the Triceps brachii muscle

Neck of the Scapula

• Location: Between the body and the head of the bone
• Features: Corresponds with scapular notch above and upper end of infraglenoid tubercle below

ANGLES OF THE SCAPULA

Superior Angle

• Located at the junction of the superior and medial borders
• Thin and smooth
• Provides attachment to a few muscle fibers

Inferior Angle

• Located at the junction of vertebral and axillary borders
• Thick and rough
• Serves as an origin point for muscles

Lateral Angle (Head of the Scapula)

• Features:
  • Thickest part of the bone
  • Supports the coracoid process
  • Contains the glenoid cavity
• Function: Articulates with the head of the humerus