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. The acromioclavicular joint transmits forces from the upper limb to the clavicle.
The ligaments around this joint are relatively weak. A hard fall onto the elbow or outstretched hand can stretch or tear the acromioclavicular ligaments, resulting in a moderate injury to the joint. However, the primary support for the acromioclavicular joint comes from a very strong ligament called the coracoclavicular ligament see Figure 8.
This connective tissue band anchors the coracoid process of the scapula to the inferior surface of the acromial end of the clavicle and thus provides important indirect support for the acromioclavicular joint.
Following a strong blow to the lateral shoulder, such as when a hockey player is driven into the boards, a complete dislocation of the acromioclavicular joint can result. In this case, the acromion is thrust under the acromial end of the clavicle, resulting in ruptures of both the acromioclavicular and coracoclavicular ligaments. The scapula then separates from the clavicle, with the weight of the upper limb pulling the shoulder downward.
The pectoral girdle, consisting of the clavicle and the scapula, attaches each upper limb to the axial skeleton. The clavicle is an anterior bone whose sternal end articulates with the manubrium of the sternum at the sternoclavicular joint. The sternal end is also anchored to the first rib by the costoclavicular ligament. The acromial end of the clavicle articulates with the acromion of the scapula at the acromioclavicular joint.
This end is also anchored to the coracoid process of the scapula by the coracoclavicular ligament, which provides indirect support for the acromioclavicular joint. The clavicle supports the scapula, transmits the weight and forces from the upper limb to the body trunk, and protects the underlying nerves and blood vessels. The scapula lies on the posterior aspect of the pectoral girdle. It mediates the attachment of the upper limb to the clavicle, and contributes to the formation of the glenohumeral shoulder joint.
This triangular bone has three sides called the medial, lateral, and superior borders. The suprascapular notch is located on the superior border. The scapula also has three corners, two of which are the superior and inferior angles. The third corner is occupied by the glenoid cavity. Posteriorly, the spine separates the supraspinous and infraspinous fossae, and then extends laterally as the acromion. The subscapular fossa is located on the anterior surface of the scapula.
The coracoid process projects anteriorly, passing inferior to the lateral end of the clavicle. Discuss two possible injuries of the pectoral girdle that may occur following a strong blow to the shoulder or a hard fall onto an outstretched hand.
Skip to content Learning Objective By the end of this section, you will be able to: Describe the bones of the pectoral girdle, and describe how the girdle unites the upper limbs with the axial skeleton including the unique features and function of each bone and joint.
Chapter Review The pectoral girdle, consisting of the clavicle and the scapula, attaches each upper limb to the axial skeleton. Review Questions. Critical Thinking Questions 1. Describe the shape and palpable line formed by the clavicle and scapula. Solutions Answers for Critical Thinking Questions The clavicle extends laterally across the anterior shoulder and can be palpated along its entire length.
The spinoglenoid notch lies posteriorly behind the neck. The scapula is surrounded by an arterial anastomosis, the scapular anastomosis which aims to ensure an adequate supply of blood to the upper limb, but has added benefit of adequate supply to the bone itself. It consists of the:. See " ossification centers of the pectoral girdle " for information on the scapular ossification centers.
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Edit article. View revision history Report problem with Article. Citation, DOI and article data. Luijkx, T. Reference article, Radiopaedia. Apart from this one very movable bony linkage, the scapula is held onto the body entirely by muscles. It's thus capable of a wide range of movement, upward and downward, and also forward and backward around the chest wall.
Looking at the clavicle from above we can see that it's slightly S-shaped, with a forward curve to its medial half. At its medial end this large joint surface articulates with the sternum. At the lateral end this smaller surface articulates with the scapula.
On the underside, massive ligaments are attached, here laterally, and here medially. The scapula is a much more complicated bone. The flat part, or blade, is roughly triangular with an upper border, a lateral border, and a medial border.
The blade isn't really flat, it's a little curved to fit the curve of the chest wall. This smooth concave surface is the glenoid fossa. It's the articular surface for the shoulder joint. Above and below the glenoid fossa are the supraglenoid tubercle, and the infraglenoid tubercle, where two tendons are attached, as we'll see. A prominent bony ridge, the spine of the scapula, arises from the dorsal surface, and divides it into the supraspinous fossa, and the infraspinous fossa.
At its lateral end the spine gives rise to this flat, angulated projection, the acromion, which stands completely clear of the bone. The clavicle articulates with the scapula here, at the tip of the acromion. This other projection, looking like a bent finger, is the coracoid process. Here's how the clavicle and the scapula look in the living body.
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