 Welcome to the appendicular skeleton, the arms, legs, and their girdles. The skeleton is divided into two major portions, the axial skeleton and the appendicular skeleton. The axial skeleton consists of the bones of the skull, the vertebral column, and the ribcage. The appendicular skeleton consists of the bones of the upper and lower limbs and the bony girdles that support them on the body trunk. This learning object examines the appendicular skeleton. The pectoral girdle is composed of two clavicles and two scapulae, one set for each arm. The clavicle, or collarbone, is easy to recognize because of its S shape. The scapula, or shoulder blade, is flat and irregular. The glenoid fossa, or cavity, forms the arm socket with the head of the humerus. All shoulder movements include the sternoclavicular joint, the only body joint attaching the girdle to the trunk, which is formed by the medial end of the clavicle and the sternum. The upper arm is called the humerus. The upper extremity of the humerus consists of the bone's large rounded head. Also located on the humerus are the coronoid and olocron fossa, which accommodate the forearm bones during movement at the elbow. The two lower arm bones are the lateral-positioned radius and medial-positioned ulna. The hand contains 27 bones including 8 carpal bones and 5 metacarpal bones. Four fingers each have three phalanges, but the thumb only has two phalanges. Hip bones that comprise the pelvic girdle are much larger than the bones in the shoulder girdle in order to help the body bear weight. The hip bones are also called the oscoxy. Each coxa is made up of the ilium, ischium, and pubis. The upper leg consists of one bone. The femur is the longest and strongest bone in your body. The lower leg has two bones, the medial, bigger, and stronger tibia, and the lateral, deeper, and inferior fibula. The seven weight-bearing tarsals or ankle bones are much larger and stronger than the wrist or carpal bones. The largest tarsal bone is the calcaneus or heel bone. Five metatarsals form the ball of the foot. The foot has a total of 26 bones including three phalanges for each toe, except for the big toe which has two. The foot also contains built-in longitudinal and transverse arches for weight support. Congratulations! You have completed this learning activity.