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The Appendicular Skeleton

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The Appendicular Skeleton

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THE APPENDICULAR SKELETON

Text Reference: CHAPTER 8

The appendicular skeleton (Chapter 8) consists of the bones of the PECTORAL GIRDLES (shoulder girdles), PELVIC GIRDLE (hip girdle), and the UPPER AND LOWER LIMBS (extremities).

Each of the 2 PECTORAL GIRDLES (shoulder girdles) (FIGS. 8.1-8.3, pp. 204-206) consists of a CLAVICLE (collar bone) and a SCAPULA (shoulder blade). Anteriorly, the medial end of each clavicle joins the CLAVICULAR NOTCH on the MANUBRIUM of the sternum (FIG. 7.23, p. 196). The lateral end of each clavicle meets the ACROMION of the scapula. The clavicle is a long bone, but it has no medullary cavity.  The clavicle supports the scapula and arms, it protects deeper structures (blood vessels, for example) in the upper chest, and it transmits impact from the arms to the axial skeleton.  The scapula is attached to the thorax and vertebral column by muscles.

The pectoral girdles attach the upper extremities (limbs) to the axial skeleton and provide attachment sites for many muscles that move the upper limbs. The 2 pectoral girdles and the associated muscles form your shoulders.

The pectoral girdles are very flexible and allow the upper limbs a great deal of flexibility. They permit movement in many directions at the shoulder joint. The socket of the shoulder joint is small, shallow, and poorly reinforced with ligaments. This arrangement is good for flexibility, but it is not very stable. Shoulder dislocations are therefore fairly common.

The UPPER LIMBS (extremities) (FIGS. 8.4-8.8) consist of 60 bones; 30 bones per limb. These are the bones of the arms, wrists, and hands. They include the HUMERUS, ULNA, RADIUS, CARPALS, METACARPALS, and PHALANGES.

The PELVIC GIRDLE (hip girdle) (FIGS. 8.9-8.11 & TABLE 8.1) attaches the lower extremities (limbs) to the axial skeleton, and it supports and protects the visceral organs of the pelvic cavity. The pelvic girdle is a strong and stable support for the lower limbs. While the shoulder...