Chapter 5 Bone formation. Growth and remodeling Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 5 Bone formation. Growth and remodeling The word skeleton comes from the Greek word meaning “dried-up body.” Our internal framework is designed and engineered to be strong and light. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Changes in the Human Skeleton In embryos, the skeleton is primarily hyaline cartilage During development, much of this cartilage is replaced by bone Cartilage remains in isolated areas Bridge of the nose Parts of ribs Joints HIGHLIGHT first bullet. Slide 5.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Fetal Bone

Bone Growth (Ossification) Epiphyseal plates allow for growth of long bone during childhood New cartilage is continuously formed Older cartilage becomes ossified (Ossification) Cartilage is broken down Bone replaces cartilage Remember that lengthwise bone growth is controlled by growth hormones. Slide 5.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Bone Growth Bones are remodeled and lengthened until growth stops Bones change shape somewhat Bones grow in width (appositional growth) The process at which bones grow in width is called appositional growth. Slide 5.13b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Long Bone Formation and Growth Figure 5.4a Slide 5.14a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Long Bone Formation and Growth Figure 5.4b Slide 5.14b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Types of Bone Cells Osteocytes Osteoblasts Osteoclasts Mature bone cells Osteoblasts Bone-forming cells Osteoclasts Bone-destroying cells Break down bone matrix for remodeling and release of calcium Bone remodeling is a process by both osteoblasts and osteoclasts Know these three cells. Control of these bone remodeling cells (osteoblasts and osteoclasts) is controlled by hormones from the parathyroid glands called Parathyroid Hormone (PTH). Osteoblasts become trapped in the layers of new matrix and become osteocytes. Slide 5.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Rickets A disease of children in which the bones fail to calcify. Rickets is usually due to a lack of calcium in the diet or lack of vitamin D, which is needed to absorb calcium into the blood.

Bone Fractures A break in a bone Types of bone fractures Closed (simple) fracture – break that does not penetrate the skin Open (compound) fracture – broken bone penetrates through the skin Bone fractures are treated by reduction and immobilization Realignment of the bone HIGHLIGHT “Open (compound) fracture – Broken bone penetrates through the skin.” Slide 5.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Common Types of Fractures Be familiar with comminuted, compression, and greenstick fractures. Table 5.2 Slide 5.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Repair of Bone Fractures Hematoma (blood-filled swelling) is formed Break is splinted by fibrocartilage to form a callus Fibrocartilage callus is replaced by a bony callus Bony callus is remodeled to form a permanent patch Slide 5.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Stages in the Healing of a Bone Fracture You need to know all four stages in the healing of a bone fracture. Figure 5.5 Slide 5.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings