Scapula Bone
Anatomy Lesson
Introduction to the Scapula
The scapula bone joins with the clavicle to form the shoulder (pectoral) girdle, which connects the humerus (upper arm bone) with the thorax.
Because much of the scapula is relatively flat, it is commonly known as the shoulder blade. Scapulae is the Latin word for the “shoulder blades.” This term was likely modified from the Greek verb “skaptein,” meaning to dig, because the bone’s flattened shape resembles a trowel or small shovel.
There are several prominent anatomical landmarks on the scapula. Most provide surface area for the 17 muscles that attach to the scapula.
Location of the Scapula Bone
Borders and Angles
The triangular scapula has three edges called the superior, medial, and lateral borders (or margins). The three corners of the scapula, where the edges converge, are called angles. The superior angle is the corner where the superior and lateral borders converge. This area provides attachment for muscles that move the neck. The inferior angle is the corner where the medial and lateral borders converge. The bone in this region is thick because it is the attachment site for several powerful muscles that move the shoulder and upper limb. The remaining corner of the scapula, the lateral angle, is where the superior and lateral borders intersect.
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Tubercles, Notches, and Cavities
A shallow depression called the glenoid cavity (or glenoid fossa) is present along the edge of the lateral angle. This area articulates with the humerus bone to form the glenohumeral joint (shoulder joint).
A small bump-like projection, the supraglenoid tubercle, is located above the glenoid cavity and can be most easily observed from a lateral view. A second bump-like projection, the infraglenoid tubercle, is below the glenoid cavity. The supraglenoid tubercle is an attachment site for the biceps brachii muscle, and the infraglenoid tubercle is an attachment site for the triceps brachii. Both of these muscles contribute to moving the arm and forearm.
An indentation called the suprascapular notch appears on the superior border medial to the base of the coracoid process. The superior transverse scapular ligament converts the notch into a foramen, which passes the suprascapular nerve.
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Projections, Ridges, and Depressions
A prominent projection, the coracoid process, emerges from the lateral end of the scapula’s superior border, inferior to the clavicle. It is hook-like in shape, extending anteriorly and curving laterally. Coracoid is a Greek word for crow or raven because the process resembles a crow’s beak. The coracoid process is anchored to the underside of the clavicle by ligaments that reinforce the acromioclavicular joint. The surface of the process is also the attachment site for muscles that move the scapula, arm, and forearm.
On the posterior side of the scapula is a prominent ridge called the scapular spine, which runs obliquely across the upper part of the bone. It primarily serves as an attachment point for several muscles that move the scapula (shoulder).
The acromion (acromial process) is a flattened and expanded lateral projection from the spine. It articulates with the lateral end of the clavicle at the acromioclavicular joint and provides a protective bony cover over the top of the shoulder joint. It is also the attachment site for the deltoid muscle that passes across the shoulder joint to move the arm.
The scapula has three depressions, each called a fossa (plural = fossae). Two are on the posterior scapula, above and below the scapular spine. Superior to the spine is the narrow supraspinous fossa, and inferior to the spine is the broad infraspinous fossa. The scapula’s anterior (deep) surface forms the broad subscapular fossa. These fossae are the attachment sites for muscles that cross the shoulder joint to act on the humerus.
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References and Attributions
NIH: National Library of Medicine – “Anatomy, Back, Scapula.”
NIH: National Library of Medicine – “Anatomy, Thorax, Scapula.”
OpenStax – “The Pectoral Girdle” (Access for free at https://openstax.org/books/anatomy-and-physiology-2e/pages/1-introduction).