The scapula bone joins with the clavicle to form the shoulder (pectoral) girdle, which connects the humerus (upper arm bone) with the thorax. The scapula is a flattened bone whose name is derived from scapulae, 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 important anatomical landmarks on the scapula. Most serve as attachment points for muscles that either stabilize the scapula or move the humerus.
The edges of the scapula are referred to as the superior, medial, and lateral borders (or margins). The corners of the triangular scapula are called angles. Joining the superior and lateral borders is the superior angle. This is an attachment point for muscles that move the neck. Joining the medial and lateral borders is the inferior angle. This is the most inferior portion of the scapula and is particularly important because it serves as the attachment point for several powerful muscles involved in the shoulder and upper limb movements. The remaining corner of the scapula, the lateral angle, joins the superior and lateral borders.
Borders and Angles
Tubercles, Notches, and Cavities
The lateral angle is the location of the glenoid cavity (or glenoid fossa). This shallow depression articulates with the humerus bone of the arm to form the glenohumeral joint (shoulder joint). The small bony bumps located immediately above and below the glenoid cavity are the supraglenoid tubercle and the infraglenoid tubercle, respectively. These provide attachments for muscles of the arm.
Lateral to the midpoint of the superior border and medial to the base of the coracoid process is the suprascapular notch. This notch is converted into a foramen by the superior transverse scapular ligament and serves for the passage of the suprascapular nerve.
Tubercles, Notches, and Cavities
Projections, Ridges, and Depressions
The scapula also has two prominent projections. Toward the lateral end of the superior border, between the suprascapular notch and glenoid cavity, is the hook-like coracoid process (coracoid = “shaped like a crow’s beak”). This process projects anteriorly and curves laterally. At the shoulder, the coracoid process is located inferior to the lateral end of the clavicle. It is anchored to the clavicle by a strong ligament and serves as the attachment site for muscles of the anterior chest and arm. On the posterior aspect, the spine of the scapula is a long and prominent ridge that runs across its upper portion. Extending laterally from the spine is a flattened and expanded region called the acromion or acromial process. The acromion forms the bony tip of the superior shoulder region and articulates with the lateral end of the clavicle, forming the acromioclavicular joint. Together, the clavicle, acromion, and spine of the scapula form a V-shaped bony line that provides for the attachment of neck and back muscles that act on the shoulder, as well as muscles that pass across the shoulder joint to act on the arm.
The scapula has three depressions, each of which is called a fossa (plural = fossae). Two of these are found 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 anterior (deep) surface of the scapula forms the broad subscapular fossa. All of these fossae provide large surface areas for the attachment of muscles that cross the shoulder joint to act on the humerus.
Projections and Depressions
OpenStax, Anatomy and Physiology
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Reference: “The Pectoral Girdle“
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Reference: “The Scapula“