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Chapter 4: The Shoulder Girdle

INTRODUCTION

Objectives

  • To identify on the skeleton important bony features of the shoulder girdle

  • To label on a skeletal chart the important bony features of the shoulder girdle

  • To draw on a skeletal chart the muscles of the shoulder girdle and indicate shoulder girdle movements using arrows

  • To demonstrate, using a human subject, all the movements of the shoulder girdle and list their respective planes of movement and axes of rotation

  • To palpate the muscles of the shoulder girdle on a human subject and list their antagonists

  • To palpate the joints of the shoulder girdle on a human subject during each movement through the full range of motion and appreciate the role of the ligaments in providing stability

  • To learn and understand the innervation of the shoulder girdle muscles

  • To determine, through analysis, the shoulder girdle movements and the muscles involved in selected skills and exercises

The entire upper extremity depends upon the shoulder girdle to serve as a base from which to function. The only attachment of the upper extremity to the axial skeleton is via the scapula and its attachment through the clavicle at the sternoclavicular joint. To enhance understanding of how the shoulder joint and the rest of the upper extremity depend on the shoulder girdle, we will discuss it separately from the other structures.

Brief descriptions of the most important bones in the shoulder region will help you understand the skeletal structure and its relationship to the muscular system.

BONES

Two bones are primarily involved in movements of the shoulder girdle. They are the scapula (irregular bone) and the clavicle (flat bone), which generally move as a unit. Their only bony link to the axial skeleton is provided by the clavicle’s articulation with the sternum. Key bony landmarks for studying the shoulder girdle are the manubrium, clavicle, coracoid process, acromion process, glenoid fossa, lateral border, inferior angle, medial border, superior angle and spine of the scapula (Figs. 4.1, 4.2, 4.3 and 4.4).

FIG. 4.1

Right shoulder girdle, anterior view.

An illustration shows the anterior view of the right shoulder girdle, consisting of the scapula, clavicle, manubrium, and sternum. The parts of the scapula are medial, lateral, or axillary, and superior borders, superior and inferior angles, subscapular fossa in the superomedial region, glenoid cavity or fossa in the superolateral edge, a suprascapular notch in the superior border, the coracoid process between the glenoid cavity and suprascapular notch, and acromion process from the posterior side of the scapula. The scapula is connected to the clavicle from the acromion process by the superior acromioclavicular ligament and from the coracoid process by the two coracoclavicular ligaments, trapezoid and conoid. The clavicle is connected to the chondral cartilage of the first rib by the costoclavicular ligament and the manubrium by the anterior sternoclavicular ligament. The interclavicular ligament extends over the manubrium.
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FIG. 4.2

Right clavicle. A, Superior view; B, Inferior view.

A 2-part illustration shows the superior and inferior views of the right clavicle. The lateral end is the acromial end and the medial end is the sternal end. Part A: In the superior view, the conoid tubercle is near the acromial end, on the lower side of the clavicle. Part B: In the inferior view, the conoid tubercle is near the acromial end, on the upper side of the clavicle.
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FIG. 4.3

Right scapula. A, Posterior view; B, Lateral view.

An illustration shows the posterior views of the right scapula. The parts are medial or vertebral, lateral or axillary, and superior borders, superior and inferior angles, infraspinous fossa in the central region, glenoid cavity or fossa in the superolateral edge, the spine of the scapula along the superior side, supraspinous fossa between the superior angle and the spine of the scapula, suprascapular notch in the superior border, and acromion process curving from the spine of the scapula. The acromion process is connected to the clavicle at the acromioclavicular joint. An illustration shows the lateral views of the right scapula. The illustration shows the lateral view, the acromion process extends from the spine of the scapula on its posterior side, the coracoid process is on the superior edge toward the anterior side, and the glenoid cavity or fossa is on the superolateral edge.
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FIG. 4.4

Right shoulder girdle surface anatomy, anterior and posterior views, respectively.

An illustration shows the anterior and posterior views of the show the upper right side of the human body. In both views, the trapezius muscle is in the upper shoulder, the deltoid muscle is on the lateral edge of the shoulder, and the acromioclavicular joint is between the two muscles. In the anterior view, the clavicle is in the upper chest, just below the trapezius muscle, and the pectoralis major muscle is in the right chest. In the posterior view, the spine of the scapula is just below the trapezius muscle, and the inferior angle of the scapula is in the center back. An illustration shows the anterior and posterior views of the show the upper right side of the human body. In both views, the trapezius muscle is in the upper shoulder, the deltoid muscle is on the lateral edge of the shoulder, and the acromioclavicular joint is between the two muscles. In the anterior view, the clavicle is in the upper chest, just below the trapezius muscle, and the pectoralis major muscle is in the right chest. In the posterior view, the spine of the scapula is just below the trapezius muscle, and the inferior angle of the scapula is in the center back.
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JOINTS

When analyzing shoulder girdle (scapulothoracic) movements, it is important to realize that the scapula moves on the rib cage as a consequence of joint motion actually occurring at the sternoclavicular joint and to a much lesser extent at the acromioclavicular joint (see Figs. 4.1...

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