Chapter 7: Skeletal System: Appendicular Division

The superior supporting structure, the pectoral girdle (or shoulder girdle), includes the S-shaped clavicle, which provides the only direct articulation between the girdle and the axial skeleton at the sternum, and the broad scapula, which features the cup-shaped glenoid cavity. The upper limb consists of the humerus, the single bone of the arm, characterized by the greater and lesser tubercles and the deltoid tuberosity. Distally, the humerus articulates with the parallel bones of the forearm, the medial ulna (with the prominent olecranon process forming the elbow point) and the lateral radius, which rotate relative to each other to enable pronation and supination. The hand skeleton is formed by the eight carpal bones of the wrist, arranged in two rows—proximal bones like the scaphoid and lunate, and distal bones like the capitate and hamate—followed by five metacarpal bones that support the palm, and fourteen phalanges (finger and thumb bones). The inferior supporting structure, the pelvic girdle, is significantly more massive for weight bearing and locomotion, formed by two hip bones, each fusing three bones: the superior ilium, the posterior ischium, and the anterior pubis, which meet at the acetabulum. The complete pelvis (two hip bones, sacrum, and coccyx) is segmented into the greater (false) and lesser (true) pelvis and exhibits clear sexual differences, with the female pelvis being generally broader, lighter, and having a wider pelvic inlet and pubic angle (100 degrees or more). The lower limb is dominated by the femur, the longest and heaviest bone, identified by the greater and lesser trochanters and the posterior linea aspera. Inferior to the femur is the patella, a sesamoid bone protecting the knee joint. The leg contains the large, medial, weight-bearing tibia, featuring the tibial tuberosity and the medial malleolus, and the slender, non-weight-bearing lateral fibula, which contributes the lateral malleolus to stabilize the ankle joint. The ankle, or tarsus, consists of seven bones, including the large calcaneus (heel bone) and the talus, which articulates with the leg bones. The foot structure is completed by five metatarsal bones and phalanges, maintained by the crucial longitudinal and transverse arches that distribute body weight during standing and walking. Finally, the chapter notes that analyzing various characteristics, particularly sex differences in the pelvis and the status of epiphyseal fusion, allows for the determination or close estimation of an individual’s sex and age from the skeleton.