Anatomy Lecture: Scapula

Introduction

• Today's topic: Scapula
• Alternative name: Shoulder blade
• Characteristics: Flat, triangular bone
• Location: Posterior aspect of the thoracic cage, across the 2nd to 7th ribs

Determination of Side

• Three main points to determine the side:
  1. Anterior vs. Posterior
  2. Medial vs. Lateral
  3. Superior vs. Inferior
• Key indicators:
  • Coracoid process facing anteriorly
  • Large glenoid cavity facing laterally
  • Thick lateral border from glenoid cavity above to inferior angle below
• Conclusion: Given scapula is the right side

Features and Attachments of the Scapula

Surfaces

1. Costal Surface (Concave, facing anteriorly):
   • Fits with ribs
   • Marked by 3-4 oblique ridges for muscular attachment (Subscapularis)
2. Dorsal Surface (Convex):
   • Divided into smaller supraspinous fossa and larger infraspinous fossa by the spine of the scapula
   • Supraspinous fossa: Origin for Supraspinatus muscle
   • Infraspinous fossa: Origin for Infraspinatus muscle
   • Structures passing through the spinoglenoid notch: Suprascapular nerve and vessels

Borders

1. Superior Border:
   • Thin and small
   • Suprascapular notch located near the root of the coracoid process
   • Suprascapular ligament attachment; suprascapular nerve passes below, artery and vein pass above
   • Origin for the inferior belly of Omohyoid muscle
2. Medial Border (Longest):
   • Extends from the superior to inferior angle
   • Coastal aspect: Insertion for Serratus anterior muscle
   • Dorsal aspect: Insertion for Levator scapulae, Rhomboid minor, Rhomboid major muscles
3. Lateral Border (Thickest):
   • Extends from glenoid cavity to inferior angle
   • Dorsal aspect gives origin to Teres minor (upper 2/3) and Teres major (lower 1/3) muscles

Angles

1. Superior Angle:
   • Junction of superior and medial borders
2. Inferior Angle:
   • Junction of medial and lateral borders
3. Lateral Angle (Head of the Scapula):
   • Contains the glenoid cavity
   • Articulates with the head of the humerus to form the shoulder joint
   • Attachment for glenoid labrum to deepen the glenoid cavity
   • Supraglenoid tubercle: Origin for the long head of Biceps brachii
   • Infraglenoid tubercle: Origin for the long head of Triceps brachii
   • Glenoid cavity: Pressure epiphysis type

Processes

1. Spine of Scapula (Spinous Process):
   • Triangular plate dividing dorsal surface
   • Superior surface: Origin for part of Supraspinatus
   • Inferior surface: Origin for part of Infraspinatus
   • Posterior border (thick): Crest of spine; insertion for Trapezius (upper lip) and origin for Deltoid (lower lip)
2. Acromion Process:
   • Flattened process, continuous with spine
   • Superior surface: Subcutaneous
   • Inferior surface: Related to subacromial bursa
   • Medial border: Oval facet for articulation with clavicle forming acromioclavicular joint; insertion for Trapezius
   • Lateral border: Deltoid tubercle for origin of Deltoid muscle
   • Example of traction epiphysis
3. Coracoid Process:
   • Directs forward and laterally
   • T-process is atavistic epiphysis
   • Superior and inferior surfaces, medial and lateral borders
   • Attachments:
     • Short head of Biceps brachii, Coracobrachialis (tip)
     • Pectoralis minor (medial border and superior surface)
     • Coracoacromial ligament (lateral border)
     • Coracohumeral ligament (root)
     • Coracoclavicular ligament (superior surface and root)

Applied Anatomy

1. Winging of the Scapula:
   • Paralysis of Serratus anterior muscle due to long thoracic nerve injury
   • Medial border becomes prominent during pushing or punching movements
2. Scaphoid Scapula:
   • Medial border becomes concave laterally (abnormal)
3. Arterial Anastomosis Around Scapula:
   • Due to blockage between subclavian artery and axillary artery
   • Visible pulsation in the scapular area

Summary

• Surfaces: Costal and dorsal surfaces
• Borders: Superior, medial, and lateral borders
• Angles: Superior, inferior, and lateral angles
• Processes: Spine, acromion, and coracoid processes
• Types of Epiphyses:
  • Glenoid cavity: Pressure type
  • Acromion process: Traction type
  • Tip of coracoid process: Atavistic type

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