The Skeletal System The Appendicular Skeleton

A8 The Skeletal System: The Appendicular Skeleton Each upper limb skeleton consists of 32 bones. The clavicle articulates medially with the manubrium of the sternum and laterally with the acromion of the scapula. The glenoid cavity of the scapula articulates with the head of the humerus to form the glenohumeral (shoulder) joint. The prominent ridge that runs along diagonally across the posterior aspect of the aspect of the scapula is called the spine. The olecranon fossa is on the posterior side of the humerus. The pectoral girdles are stabilized by a large group of muscles that extend from the vertebral column and ribs to the scapula. The humerus is the longest and largest bone of the upper limb. In the forearm, the longer ulna is on the medial side, and the shorter radius is on the lateral side. The skeleton of the hand consists of the proximal carpals, the intermediate metacarpals, and the distal phalanges. The ulnar nerve is palpated when hitting the “funny bone.” The deltoid tuberosity serves as a point of attachment for which deltoid. Distally, the metatarsals articulate with the proximal row of phalanges to form the metatarsophalangeal joints. A boxer’s fracture is a fracture of the 5 th metacarpal and can occur when a person hits another with a closed fist. Each lower limb skeleton consists of 30 bones. The acetabulum is the socket for the head of the femur where the three parts of the hip bone converge and ossify. The hip bones, sacrum, coccyx, and pubic symphysis form the bony pelvis. The greater pelvis is separated from the lesser pelvis by the pelvic inlet. The lesser and greater pelves are separated by the pelvic inlet. The patella articulates with the lateral and medial condyles of the femur. The femur, or thigh bone, is the longest, heaviest, and strongest bone in the body. The lateral condyle of the femur articulates with the lateral condyle of the tibia bone. Damage to the greater trochanter would hinder the function of some muscles of the buttocks, thigh, and hip abduction. A8 The Skeletal System: The Appendicular Skeleton The tibia articulates with the femur and fibula proximally, and with the fibula and talus distally. The skeleton of the foot consists of the proximal tarsals, the intermediate metatarsals, and the distal phalanges. Each slender, S-shaped clavicle, or collarbone, lies horizontally across the anterior part of the thorax superior to the first rib. The humerus forms a direct articulation proximally with the scapula. The largest and strongest of the tarsals is the calcaneus. The tarsus (ankle) is the proximal region of the foot and consists of seven tarsal bones. Joints between tarsal bones are called intertarsal joints. The medial malleolus is on the tibia bone. A dislocated shoulder involves separation of the humerus from the scapula. The glenoid cavity of the scapula accepts the head of the humerus. The true wrist or carpus consists of a group of eight short bones united by ligaments. Most of a person’s body weight is absorbed by the talus and the calcaneus. Pectoral refers to the chest or breast. The prominence of the elbow is formed by the olecranon of the ulna. The pectoral girdles form the articular base for the bones of the free upper limbs and anchor the upper limb to the axial skeleton via a series of muscles. Each upper limb has 30 bones in three locations – the arm (humerus); the forearm (ulna and radius); and the hand (wrist); 4 metacarpal bones in the metacarpus (palm); and 14 phalanges in the digits. The navicular articulates with the second cuneiform. The rounded superior end of the patella is called the base. The scaphoid is the most frequently broken carpal bone. The clavicle has a slight S-shaped curve and attaches to the sternum and the scapula. After the limb buds develop, endochondral ossification of the free limb bones begins by the end of the eighth embryonic week. Together, the bones, muscles, and joints form an integrated system called the musculoskeletal system. A8 The Skeletal System: The Appendicular Skeleton The branch of medicine science concerned with the prevention or correction of disorders of the musculoskeletal system is called orthopedics. Clubfoot (talipes equinovarus) – an inherited deformity in which the foot is twisted inferiorly and medially, and the angle of the arch is increased; occurs in 1 of every 1000 births Fractured clavicle – a fracture resulting from excessive mechanical force transmitted from the free upper limb to the trunk, or a blow to the superior part of the anterior thorax Genu valgum – a deformity in which the knees are abnormally close together and the space between the ankles is increased due to a lateral angulation of the tibia in relation to the femur Hallux valgus – angulation of the great toe away from the midline of the body, typically caused by wearing tightly fitting shoes