Anatomy of the Scapula: A Comprehensive Guide

The scapula, commonly known as the shoulder blade, is a fascinating bone that plays a vital role in the functioning of the shoulder region. This blog provides an in-depth exploration of its anatomy, from its structure to its articulations, and the various muscles and ligaments attached to it.

Introduction

• The scapula is a bone located in the shoulder region.

• It contributes to the formation of the shoulder girdle.

• This thin, flat bone has a triangular shape and is positioned in the posterolateral aspect of the thoracic cage.

• It extends from the 2nd to the 7th rib and has two major articulations:

  • Glenohumeral Articulation: Between the glenoid cavity of the scapula and the head of the humerus.

  • Acromioclavicular Articulation: Between the medial border of the acromion process and the lateral end of the clavicle.

Anatomical Position and Side Determination

• The coracoid process is directed forward.

• The spinous process points backward.

• The inferior angle is directed downward.

• The glenoid cavity is oriented forward, laterally, and slightly upward.

• The side of the scapula can be determined by observing the direction of the glenoid cavity (e.g., if it faces left, it is the left scapula).

Structures of the Scapula

Surfaces

1. Costal Surface (Subscapular Fossa)

   • Concave and directed anteromedially.

   • Contains three longitudinal ridges.

2. Dorsal Surface

   • Convex and gives rise to the spinous process.

   • Divided into two parts by the spinous process:

     • Upper smaller part: Supraspinous fossa.

     • Lower larger part: Infraspinous fossa.

Borders

1. Superior Border

   • Thinnest and smallest of all borders.

   • Extends from the superior angle to the root of the coracoid process.

   • Features the suprascapular notch.

2. Medial Border (Vertebral Border)

   • Longest border, extending from the superior to the inferior angle.

3. Lateral Border (Axillary Border)

   • Thickest border, extending from the lower end of the glenoid cavity to the inferior angle.

Angles

1. Superior Angle

   • Formed at the junction of the superior and medial borders.

   • Covered by the trapezius muscle.

2. Inferior Angle

   • Formed at the junction of the medial and lateral borders.

   • Positioned opposite the 7th rib.

3. Lateral Angle (Glenoid Angle)

   • Formed at the junction of the superior and lateral borders.

   • Contains the glenoid cavity and the supraglenoid tubercle.

Processes

1. Spinous Process (Spine of Scapula)

   • Located on the dorsal surface.

   • Divided into an apex and three borders (anterior, posterior, lateral) with two surfaces (superior and inferior).

   • The posterior border, also known as the crest of the spine, features upper and lower lips.

   • The lateral border forms the medial boundary of the spinoglenoidal notch.

2. Acromion Process

   • Projects forward from the lateral end of the spinous process.

   • Contains two borders (medial and lateral) and two surfaces (superior and inferior).

   • The medial border articulates with the clavicle to form the acromioclavicular joint.

3. Coracoid Process

   • Arises from the upper part of the glenoid cavity.

Fossae

1. Supraspinous Fossa: Above the spinous process.

2. Infraspinous Fossa: Below the spinous process.

Neck

• Anatomical Neck: A constricted part of the bone located medial to the glenoid margin.

Tubercles

1. Supraglenoid Tubercle: Above the glenoid cavity.

2. Infraglenoid Tubercle: Below the glenoid cavity.

Notches

1. Suprascapular Notch

   • Located on the superior border.

   • The suprascapular ligament converts it into a foramen, providing a pathway for the suprascapular nerve.

2. Spinoglenoidal Notch

   • Located between the spinous process and the glenoid cavity.

Attachments

Muscles (17)

Insertions (6)

1. Serratus Anterior: Anterior aspect of the medial border.

2. Levator Scapulae: Posterior aspect of the medial border.

3. Rhomboid Minor: Posterior aspect of the medial border.

4. Rhomboid Major: Posterior aspect of the medial border.

5. Trapezius: Posterior border of the clavicle, medial margin of the acromion, and medial end of the spinous process.

6. Pectoralis Minor: Tip of the coracoid process.

Origins (11)

1. Subscapularis: Costal surface of the scapula.

2. Supraspinatus: Supraspinous fossa.

3. Infraspinatus: Infraspinous fossa.

4. Deltoid:

   • Anterior fiber: Anterior border of the clavicle.

   • Middle fiber: Lateral border of the acromion process.

   • Posterior fiber: Lower lip of the spinous process.

5. Biceps Brachii:

   • Long head: Supraglenoid tubercle.

   • Short head: Tip of the coracoid process.

6. Triceps Brachii:

   • Long head: Infraglenoid tubercle.

   • Medial and lateral heads: Posterior surface of the humerus.

7. Teres Minor: Lateral border (posterior aspect).

8. Teres Major: Lateral border (posterior aspect, below teres minor).

9. Latissimus Dorsi: Inferior angle (posterior aspect).

10. Coracobrachialis: Tip of the coracoid process.

11. Omohyoid:

    • Superior belly: Superior border.

    • Inferior belly: Intermediate tendon.

Ligaments

1. Superior, Middle, and Inferior Glenohumeral Ligaments.

2. Coracohumeral Ligament.

3. Transverse Humeral Ligament.

4. Ulnar and Radial Collateral Ligaments.

This detailed overview of the scapula provides essential insights for understanding its structure, functions, and clinical significance. For any queries or further learning, stay connected with Sedative Physio!