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Ossification Centers in a 12week-old Fetus Figure 5.32 Types of Bone Cells • Osteocytes—mature bone cells • Osteoblasts—bone-forming cells • Osteoclasts—bone-destroying cells – Break down bone matrix for remodeling and release of calcium in response to parathyroid hormone • Bone remodeling is performed by both osteoblasts and osteoclasts Articular cartilage Hyaline cartilag e Spongy bone New center of bone growth New bone forming Epiphyseal plate cartilage Growth in bone width Medullary cavity Bone starting to replace cartilage Growth in bone length Blood vessels New bone forming Bone collar Hyaline cartilage model Epiphyseal plate cartilage Figure 5.4a, step 3 In an embryo (a) In a fetus In a child Articular cartilage Hyaline cartilag e Spongy bone New center of bone growth New bone forming Epiphyseal plate cartilage Growth in bone width Medullary cavity Bone starting to replace cartilage Growth in bone length Blood vessels New bone forming Bone collar Hyaline cartilage model Epiphyseal plate cartilage Figure 5.4a, step 3 In an embryo (a) In a fetus In a child The Fetal Skull Figure 5.13b Skeletal Changes Throughout Life • Adolescence – Epiphyseal plates become ossified and long bone growth ends • Size of cranium in relationship to body Skeletal Changes Throughout Life Figure 5.33a Bone Fractures • Fracture—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 Dislocation of the glenohumeral joint 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 Stages in the Healing of a Bone Fracture Hematoma Hematoma formation Figure 5.5, step 1 Stages in the Healing of a Bone Fracture Hematoma External callus Internal callus (fibrous tissue and cartilage) New blood vessels Spongy bone trabecula Hematoma formation Fibrocartilage callus formation Figure 5.5, step 2 Stages in the Healing of a Bone Fracture Hematoma External callus Internal callus (fibrous tissue and cartilage) Bony callus of spongy bone New blood vessels Spongy bone trabecula Hematoma formation Fibrocartilage callus formation Bony callus formation Figure 5.5, step 3 Stages in the Healing of a Bone Fracture Hematoma External callus Internal callus (fibrous tissue and cartilage) Bony callus of spongy bone New blood vessels Healed fracture Spongy bone trabecula Hematoma formation Fibrocartilage callus formation Bony callus formation Bone remodeling Figure 5.5, step 4 Inflammatory Conditions Associated with Joints • Bursitis—inflammation of a bursa usually caused by a blow or friction • Arthritis—inflammatory or degenerative diseases of joints – Over 100 different types – The most widespread crippling disease in the United States Clinical Forms of Arthritis • Osteoarthritis – Most common chronic arthritis – Probably related to normal aging processes • Rheumatoid arthritis – An autoimmune disease—the immune system attacks the joints – Symptoms begin with bilateral inflammation of certain joints – Often leads to deformities Clinical Forms of Arthritis • Gouty arthritis – Inflammation of joints is caused by a deposition of uric acid crystals from the blood – Can usually be controlled with diet The Vertebral Column Figure 5.16 Skeletal Changes Throughout Life • Osteoporosis – Bone-thinning disease afflicting • 50% of women over age 65 • 20% of men over age 70 – Disease makes bones fragile and bones can easily fracture – Vertebral collapse results in kyphosis (also known as dowager’s hump) – Estrogen aids in health and normal density of a female skeleton Skeletal Changes Throughout Life Figure 5.34 Skeletal Changes Throughout Life Figure 5.35