Chapter 6 Osseous Tissue and Skeletal Structure Lecture Outline Skeletal system: bones, cartilage, ligaments, CT Functions: 1. support 2. storage 3. hematopoiesis 4. protection 5. leverage Bone classification Skeleton 1. Axial support 2. Appendicular movement Shape 1. Long bones 2. Short bones 3. Flat bones 4. Irregular bones 5. Sesamoid bones 6. Sutural bones Bone structure Bone tissue 1. Compact bone 2. Spongy / Cancellous bone Long bone structure 1. Diaphysis 2. Medullary / Marrow cavity Yellow marrow 3. Epiphysis Red marrow 4. Epiphyseal line or Epiphyseal plate Metaphysis 5. Periosteum outer: dense irregular CT inner: cellular 6. Endosteum 7. Articular cartilage Joint / Articulation Joint capsule Synovial membrane Synovial fluid Flat bone structure compact bone spongy bone red marrow hematopoiesis Bone histology: osseous tissue Characterisitics: 1. dense matrix, calcium salts 2. osteocytes in lacunae 3. canaliculi 4. periosteum Matrix (98%) 1/3 osteoid collagen 2/3 hydroxyapatite calcium + phosphate Cells (2%) 1. Osteocytes Lacunae Lamellae Canaliculi Gap junctions 2. Osteoblast Osteogenesis Osteoid Hydroxyapatite 3. Osteoprogenitor cell Endosteum Cellular periosteum 4. Osteoclasts Osteolysis Structure of compact bone Osteon Central canal Perforating canal Concentric lamella Osteocytes Lacunae Canaliculi Interstitial lamellae Circumferential lamellae Structure of spongy bone Trabeculae Red marrow Periosteum 1. fibrous outer layer: dense irregular CT 2. cellular inner layer: osteoprogenitor cells Functions: 1. isolation 2. attachment 3. vessel entry 4. growth and repair Endosteum cellular: osteoprogenitor cells growth and repair Bone growth Osteogenesis = Ossification Not calcification A. Intramembranous ossification flat bones 1. ossification center forms in mesenchyme mesenchymal cells → osteoblasts 2. osteoid forms osteoblast secrete osteoid mineralized osteoblasts → osteocytes Amy Warenda Czura, Ph.D.1SCCC BIO130 Chapter 6 Handout3. spongy bone and periosteum forms mineralized osteoid → trabeculae mesenchyme → periosteum 4. compact bone forms trabeculae under periosteum → lamellar red marrow B. Endochondrial ossification long bones 1. primary ossification center forms in cartilage chondrocytes enlarge, die calcification of matrix 2. blood vessel growth cellular perichondrium → osteoblasts osteoid bone collar 3. capillaries and fibroblast migrate fibroblast → osteoblasts spongy bone 4. remodeling osteoclasts : trabeculae → marrow cavity increase length: epiphyseal plate: interstitial growth ossification increase diameter: periosteum: appositional growth 5. secondary ossification centers 6. epiphyses spongy bone articular cartilage epiphyseal closure Bone remodeling Osteoclasts lysosomal enzymes HCl Osteoblasts osteoid alkaline phosphatase Skeleton as calcium reserve blood calcium: 9-11mg/100ml Homeostasis factors 1. storage in bones 2. absorption in GI 3. excretion in kidney Too low: parathyroid hormone from parathyroid gland 1. ↑ osteoclast activity ↓ storage 2. ↑ calcitriol ↑ absorption 3. ↓ excretion Too high: calcitonin from thyroid gland 1. ↓ osteoclast activity ↑ storage 2. ↑ excretion Nutritional and hormone effects on bone 1. Calcium and Phosphate salts 2. Calcitriol (Vitamin D) 3. Vitamin C 4. Vitamin A (Carotene) 5. Vitamins K and B12 6. Growth Hormone 7. Thyroxin 8. Estrogens and Androgens 9. Calcitonin 10. Parathyroid hormone Abnormalities Genetic/Physiological 1. Giantism 2. Acromegally 3. Pituitary dwarfism Diet 1. Scurvy 2. Osteomalacia / Rickets Fracture 1. hematoma 2. callus formation periosteum → external callus: fibrocartilage endosteum → internal callus: spongy bone 3. external callus → spongy bone 4. remodeling spongy bone → compact bone Aging osteopenia female: 8% / decade male: 3% / decade osteoporosis Amy Warenda Czura, Ph.D.2SCCC BIO130 Chapter 6 HandoutMetaphysisMetaphysisArticular cartilageRed marrow(fills spaces)Structure of a long boneStructure of a long boneAmy Warenda Czura, Ph.D.3SCCC BIO130 Chapter 6 HandoutBone cellsBone cellsCompact bone histologyCompact bone histologySpongy bone histologySpongy bone histologyAmy Warenda Czura, Ph.D.4SCCC BIO130 Chapter 6 HandoutIntermembranous Ossification/OsteogenesisIntermembranous Ossification/OsteogenesisSpongyaround spongy boneAmy Warenda Czura, Ph.D.5SCCC BIO130 Chapter 6 HandoutEndochondrial Ossification/OsteogenesisEndochondrial Ossification/Osteogenesis1. Primary Ossification Center begins to form: chondrocytes in the diaphysis enlarge, and surrounding matrix calcifies killing the enclosedchondrocytes.2. Blood vessels grow into edge of cartilage. Cells of inner layer of perichondrium differentiate into osteoblasts which secrete osteoid. Osteoid ismineralized and a bone collar forms around the diaphysis.3. Capillaries and fibroblast migrate into the primary ossification center. Fibroblast differentiate into osteoblasts and secrete osteoid which ismineralized into trabeculae. Spongy bone is formed and continues forming growing toward the epiphyses.4. Remodeling occurs:osteoclasts degrade trabeculae in the center to create the marrow cavity. The bone increases in length by interstital growthof the epiphyseal plate followed by replacement of plate cartilage by spongy bone. (Cartilage continues to grow on epiphyseal side and isreplaced by bone on diaphysis side.) The bone increases in diameter by appositional growth from the cellular layer of periosteum.5. Secondary ossification centers form in the epiphyses.6. The epiphyses become ossified with spongy bone. Hyaline cartilage remains on articular surfaces (not calcified or ossified). Ossificationcontinues at both 1° and 2° ossification centers until all