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Unformatted text preview: Chapter 8: The Appendicular Skeleton Chapter Overview The appendicular skeleton consists of the bones of the upper and lower limbs and the pectoral and pelvic girdles that attach them to the axial skeleton. As humans, our upper limbs are freed from locomotion and, although we have the same bones as other mammals, our extraordinary ability to manipulate our environment has led to modifications. Our lower limbs are adapted for weight-bearing associated with bipedalism. Pectoral Girdle The pectoral girdle supports the arm, and consists of the clavicle and scapula. Clavicle The clavicle acts as a strut that braces the shoulder and holds the upper limb away from the midline of the body. It articulates medially with the sternum and laterally with the scapula. The sternal end has a rounded head while the acromial end is flattened. Inferiorly, a volcano-like protrusion, the conoid tubercle, provides attachment for a ligament. Scapula The scapula is a triangular-shaped bone that rests on the dorsal thoracic cage over ribs 2-7. It articulates laterally with the humerus. The superior, medial, and lateral borders form the edges of the scapula. The spine is a transverse dorsal ridge that ends laterally in a flattened extension called the acromion process. Superior to the spine is a depression called the supraspinous fossa, whereas the broad surface inferior to the spine is the infraspinous fossa. The smooth anterior surface that faces towards the ribs is the subscapular fossa. In life, these concavities serve as attachment for muscles. Laterally, anterior to the acromion process is a finger of bone, the coracoid process. The smooth, ovoid glenoid cavity articulates with the head of the humerus. The Upper Limb The upper limb consists of the following segments. The brachium (arm) extends from shoulder to elbow. The antebrachium (forearm) extends from elbow to wrist. The carpus (wrist) is between the forearm and hand. The upper limb ends in the manus (hand). Humerus 50 The humerus is the bone in the brachium. The round head articulates with the glenoid cavity of the scapula. The raised and roughened greater and lesser tubercles at the proximal end that serve to attach muscles are separated by the intertubercular groove. On the lateral surface of the shaft is a rugged triangular deltoid tuberosity, the insertion point for the deltoid muscle. The lateral and medial epicondyles flare out from the distal shaft. On the lateral side of the distal end is the capitulum, a round feature that...
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This note was uploaded on 02/09/2012 for the course BIO 102 taught by Professor William during the Spring '11 term at Harvard.
- Spring '11