Anatomy & Physiology I and II

Anatomy & Physiology Study Guide

©2018 Achieve Test Prep Page 81 of 367 Greenstick: Incomplete fracture where one side of the bone breaks and the other side bends; common in children 7.8 Aging The bones of the skeleton become thinner and weaker as a normal part of the aging process. Inadequate ossification is called osteopenia. All humans experience some measure of osteopenia with aging. This reduction in bone mass begins between ages 30 and 40. Over that period, osteoblast activity begins to decline, while osteoclast activity continues at previous levels. Once the reduction begins, women lose roughly eight percent of their skeletal mass every decade, whereas the skeletons of men deteriorate at about three percent per decade. Not all parts of the skeleton are equally affected. Epiphyses, vertebrae, and the jaws lose more mass than other sites, resulting in fragile limbs, reduction in height, and loss of teeth. When the reduction in bone mass is sufficient to compromise normal function, the condition is osteoporosis. The fragile bones are likely to break when exposed to stresses that younger individuals could easily tolerate. 7.7 Fractures A fracture is a crack or break in a bone. Despite its mineral strength, bone can crack or even break if subjected to extreme loads, sudden impacts, or stresses from unusual directions. Most fractures heal even after severe damage, provided that the blood supply and the cellular components of the endosteum and periosteum survive. Fractures are named according to their appearance, their location, and the nature of the crack in the bone itself: • Nondisplaced: Bone ends retain their normal position • Displaced: Bone ends are out of normal alignment • Complete: Bone is broken all the way through • Incomplete: Bone is not broken all the way through • Linear: The fracture is parallel to the long axis of the bone • Transverse: The fracture is perpendicular to the long axis of the bone • Compound (open): Bone ends penetrate the skin • Simple (closed): Bone ends do not penetrate the skin • Comminuted: Bone fragments into three or more pieces; common in the elderly • Spiral: Ragged break when the bone is excessively twisted; common sports injury • Depressed: Broken bone portion pressed inward; typical skull fracture • Compression: Bone is crushed; common in porous bones • Epiphyseal: Epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying •