Anatomy & Physiology

Anatomy & Physiology Study Guide

The Ribs The human body has 12 paired ribs. Ribs , or costae, are long, curved, flattened bones that form the walls of the thoracic cavity and originate on or between the thoracic vertebrae. Humans have 12 pairs of ribs. The first seven pairs are called true ribs , or vertebrosternal ribs. The vertebrosternal ribs gradually increase in length and radius of curvature beginning with the first rib. The others are called false ribs because they do not attach directly to the sternum. The Sternum The adult sternum, or breastbone, is a flat bone located in the anterior midline of the thoracic wall. The sternum has three components: 1) the manubrium, which is the widest and most superior portion of the sternum, 2) the tongue-shaped body that attaches to the inferior surface of the manubrium and extends inferiorly along the midline, and 3) the xiphoid process, the smallest part of the sternum, which is attached to the inferior surface of the body. 8.2 Appendicular Skeleton The remaining 60 percent of the bones that make up the skeletal system are appended or attached to the axial skeleton. The appendicular skeleton includes the bones of the limbs and the supporting elements, or girdles, which connect them to the trunk. The appendicular skeleton consists mainly of long bones that support the limbs. Each long bone shares common features with other long bones. For example, one epiphysis is usually called the head, the shaft is the diaphysis, and the head and shaft are speared by a neck. The Pectoral Girdle The pectoral girdle attaches to the upper limbs and consists of the clavicles and scapulae. Each arm articulates with the trunk at the pectoral girdle or shoulder girdle. The pectoral girdle consists of two S-shaped clavicles (collarbones) and two broad, flat scapulae (shoulder blades). The medial, anterior end of each clavicle articulates with the manubrium of the sternum. These articulations are the only direct connections between the pectoral girdle and the axial skeleton. The Upper Limbs The upper limbs are designed for a great range of motion. The skeleton of the upper limbs consists of the bones of the arms, forearms, wrists, and hands. At the proximal end of the humerus (bone of the upper arm), the round head articulates with the scapula. The prominent greater tubercle is a rounded projection on the lateral surface of the epiphysis, near the margin of the humeral head. The greater tubercle establishes the lateral contour of the shoulder. The lesser tubercle is a smaller projection that lies on the anterior, medial surface of the epiphysis. The ulna and radius are parallel bones of the forearm. In the anatomical position, the ulna lies medial to the radius. The olecranon , the superior end of the ulna, is the point of the elbow. The radius is the lateral bone of the forearm.

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