1. Chapter 6

2. Skeletal Cartilage Chondrocytes in lacunae in jelly- like ground substance Ground substance of water & protein  resiliency No blood or nerves Perichondrium 3 types Hyaline cartilage Elastic cartilage Fibrocartilage

3. Cartilage Types

4. Cartilage Growth Appositional growth Growth from outside Chondroblasts in perichondrium create matrix on outside of existing cartilage Interstitial growth Growth from inside Chondrocytes create matrix within lacunae Calcifified cartilage when Ca 2+ salts deposited Not bone

5. Axial Protection and support Appendicular Locomotion and manipulation Storage and hematopoiesis too Classifying Bones

6. Bone Shape 206 bones (adult) Long Short Flat Irregular Sesamoid and wormian Not 206

7. Bone Structure Markings (table 6.1) Projections Grow from bone Attachment for muscles or form joints Tuberosity, crest, trochanter, line, tubercle, epicondyle, spine, process, head, facet, condyle, ramus Depressions Conduits for nerves and blood vessels Groove, fissure, foramen, notch, meatus, sinus, fossa Helps for lab too Types Compact (osteon) Spongy (trabeculae)

8. Long Bone Anatomy Diaphysis Epiphyses Articular surface absorb stress Epiphyseal plate  hyaline Membranes Periosteum Outer is dense irregular CT Inner is osseous cells Nutrient foramina Sharpey’s fibers Endosteum Covers trabeculae Osseous cells Marrow cavities

9. Other Bone Anatomy Membranes same as long bones Diploë No dia- or epiphysis Bone marrow, but no cavity

10. Composition of Osseous Tissue Cell types Osteoprogenitor cells Osteoblasts Osteocytes Osteoclasts Matrix Osteoid (organic) Ground substance and collagen fibers Structure & strength  resist stretching and twisting Hydroxyapatites (mineral salts) Calcium phosphates Hardness  resist compression

11. Bone Formation Ossification of fetal skeleton around 8 weeks Intramembranous ossification Flat bones Fibrous membrane is calcified, no cartilage present Endochondral ossification All other bones Hyaline cartilage templates Growth Hormonally controlled hGH, thyroid hormones (T 3 and T 4 ), and sex hormones Length Interstitial growth at growth plates Width Appositional growth Remodeling and repair

12. Intramembranous Ossification Increased vascularization allows mesenchymal cells to become osteogenic cells  osteoblasts Osteoblasts produce osteoid Trapped osteoblasts become osteocytes Osteoid is calcified by hydroxyapatite Forms spicules  trabeculae around blood vessels Vascularized mesenchyme  periosteum Outer trabeculae thicken  compact bone Inner diploë persist Red marrow fills spaces Fig. 6.8

13. Endochondral Ossification Chondrocytes hypertrophy Signals calcification of cartilage Chondrocytes die = matrix deteriorates = lacunae remain Chondroblasts continue to divide = lengthening Periosteal bud enters cavitites Perichondrium is vascularized  periosteum Mesenchyme to osteoblasts Osseous cells invade Osteoid produced along hyaline template Osteoclasts break down  spicules, Osteoblasts add osteoid  trabeculae Osteoclasts erode  medullary cavity Process repeats in epiphyses soon after birth No medullary cavity forms

14. Endochondral Ossification

15. Epiphyseal (Growth) Plates Resting zone No bone growth, looks like hyaline Proliferative zone Tall stacks of chondrocytes Mitotic division  bone lengthens Hypertrophic zone Chondrocytes enlarge, signal calcify Calcification/ossification zone Chondrocytes die  spicules remain Osteoblasts turn spicules into trabeculae Osteoclasts destroy  medullary cavity lengthen

16. Thickening of Bone Osteoblasts Create new osteons on external surface Osteoclasts Break down (resorb) bone on endosteal surface

17. Bone Remodeling Antagonistic processes Bone deposit Bone resorption (removal) Continuously occurring Same rates = healthy Disrupted homeostasis = breaks Ca 2+ from bone when low Osteoclasts Ca 2+ added/redeposited as needed Osteoblasts Bone replacement Spongy: 3 – 4 years Compact: about 10 years

18. Homeostatic Control of Calcium Blood Ca 2+ levels signal Parathyroid hormone (PTH) Osteoclast resorption Only osteoid is safe  no salts Mechanical stresses influence Ca 2+ release from bone matrix Calcitonin (negligible) Inhibits resorption Ca 2+ salts deposited into bone matrix Vitamins A, C, D, and B 12 help

19. Fractures Treated by reduction Closed – physicican sets Open –pins/wires Cast immobilizes Types Closed (simple) Open (compound) Comminuted Compression Depressed Spiral Epiphyseal Smith’s Colle’s Transverse Impacted Greenstick Pott’s

20. Bone Repair Hematoma forms  kills cells Inflammatory response Fibrocartilaginous callus Phagocytes & osteoclasts clean debris Fibroblasts & chondrocytes lay down collagen and cartilage to connect Osteoblasts lay down spongy bone Excess bone on exterior and in cavity removed Compact bone recreates shaft

21. Bone Disorders Osteomalacia (rickets): inadequate mineralization of bone Osteoporosis: bone resporption faster than deposit Spina bifida: incomplete closure of vertebrae Achondroplasia: dwarfism; defective cartilage growth and improper endochondral ossification Acromegaly: gigantism; growth plate slow to ossify Scoliosis: lateral curve of spine Kyphosis: hunckback spine; exaggerated thoracic curvature Lordosis: swayback; exaggerated lumbar curvature Cleft palate: palatine bones don’t fuse Carpal tunnel syndrome: nerve impairment in wrist