Chapter 6 Skeletal System: Bones and Bone Tissue

1. Chapter 6 Skeletal System:Bones and Bone Tissue

2. Functions of the Skeletal System • Support • Protection • Movement • Storage • Hemopoiesis

3. Cartilage • Types • Hyaline cartilage • Fibrocartilage • Elastic cartilage • Fiber types • Collagen • Proteoglycans • Elastic Fibers

4. Hyaline Cartilage • Consists of specialized cells that produce matrix • Cells • Chondroblasts • Chondrocytes • Perichondrium • Growth • Appositional • Interstitial

6. Bone Shapes • Long • Upper and lower limbs • Short • Carpals and tarsals • Flat • Ribs, sternum, skull, scapulae • Irregular • Vertebrae, facial

7. Long Bone Structure • Diaphysis • Shaft • Compact bone • Epiphysis • End of the bone • Cancellous bone • Epiphyseal plate • Growth plate • Epiphyseal line • Bone stops growing in length

8. Long Bone Structure • Medullary cavity • Red marrow • Yellow marrow • Periosteum • Outer bone surface • Sharpey’s fibers • Attachment • Endosteum • Lines bone cavities

9. Flat, Short, Irregular Bones • Flat Bones • No diaphyses, epiphyses • Diploe bone • Sandwich of cancellous between compact bone • Short and Irregular Bone • Compact bone that surrounds cancellous bone center • No diaphyses and not elongated

13. Bone Histology • Bone Matrix • Organic - Collagen and proteoglycans • Inorganic - Hydroxyapatite(Calcium and Phosphate) • Bone Cells • Osteoprogenitors (stem cells) – produce osteoblasts • Osteoblasts – produce mineralized bone matrix • Osteocytes – mature bone cells • Osteoclasts – enzymatically break down bone

14. Bone Matrix

15. Bone Cells • Osteoblasts • Formation of bone through ossification or osteogenesis • Osteocytes • Mature bone cells • Lacunae: Spaces • Canaliculi: Canals • Osteoclasts • Responsible for bone resorption

16. Bone Types • Woven Bone - Collagen fibers randomly oriented • Formed during fetal development or during fracture repair • Lamellar Bone – Mature bone in sheets • Cancellous Bone • Trabeculae – interconnecting rods of bone • Stress Lines • Compact Bone • Osteon - concentric lamellae • Haversion canal, Volkman’s Canal, Lacunae and Canaliculi

17. Cancellous Bone • Consists of trabeculae • Oriented along lines of stress

20. Compact Bone • Central or haversian canals: Parallel to long axis • Lamellae: Concentric, circumferential, interstitial • Osteon or haversian system: Central canal, contents, associated concentric lamellae and osteocytes • Perforating or Volkmann’s canal: Perpendicular to long axis

23. Bone Development • Intramembranous ossification • Develops in a membrane of connective tissue. • Centers of ossification • Mesenchyme forms osteoprogenitors • Internal vs external ossification • Fontanels • Endochondral ossification • Develops in cartilage • Primary and secondary ossification centers • Both methods of ossification • Produce woven bone that is then remodeled • After remodeling, formation cannot be distinguished as one or other

24. Intramembranous Ossification

29. Endochondral Ossification • Production of a cartilage model • Embryonic mesenchyme becomes chondroblasts. • Chrondroblasts produce cartilage template with perichondrium. • Chondrocytes hypertrophy. • Cartilage is calcified and Chondrocytes die. • Ossification of cartilage model • Osteoprogenitor become osteoblasts. • Blood vessels and osteoblasts invade cartilage template. • Osteoblasts produce bone matrix at ossification centers • Endochondral bone is remodeled.

30. Endochondral Ossification

31. Endochondral Ossification

32. Endochondral Ossification

33. Growth in Bone Length • Appositional growth • New bone on old bone or cartilage surface • Epiphyseal plate zones • Resting cartilage • Proliferation • Hypertrophy • Calcification

34. Fig. 6.14

35. Growth in Bone Length

37. Zones of Bone Growth • Epiphyseal plate • Interstitial growth of cartilage • Appositional growth of bone. • Results in an increase in length of diaphysis • Articular Cartilage • Increases size of epiphysis • Growth in bones that don’t have an epiphyseal plate • Periosteum • Increases the diameter of bone. • Endosteum • Increases the circumference of trabeculae.

38. Bone Remodeling • Coverts woven bone into lamellar bone • Bone constantly removed by osteoclasts and new bone formed by osteoblasts

39. Growth in Bone Width

40. Factors that Affect Bone Growth • Genetic Factors • Nutrition • Vitamin D • Necessary for absorption of calcium from intestines • Insufficient causes rickets and osteomalacia • Vitamin C • Necessary for collagen synthesis by osteoblasts • Deficiency results in scurvy • Hormones • Growth hormone • Giantism, Acromegaly • Dwarfism (pituitary vs achondroplastic) • Thyroid hormone • Steroids (estrogen and testosterone)

42. Bone Repair • Hematoma formation • Internal Callus formation • Consists of fibrocartilage • External Callus formation • Bone-cartilage collar that stabilizes the fracture • Cartilage Ossification • Remodeling of the bone

43. Bone Repair

44. Osteogenesis Imperfecta

45. Calcium Homeostasis • Bone is the major storage site for calcium in the body • Calcium moves into bone as osteoblastsbuild new bone • Calcium moves out of bone as osteoclasts break down bone • When osteoclast and osteoblast activity is balanced, the movement of calcium in and out is equal

48.  Decreasing blood Calcium Parathyroids Parathyroid hormone . Kidneys Bone Active Vitamin D Reabsorption of Calcium Dissolution of CaPO4 crystals Small Intestine Increased blood Calcium Increased Calcium absorption in

49. Calcium Homeostasis

50. Effects of Aging on Skeletal System • Bone Matrix decreases • Bone Mass decreases • Increased bone fractures • Bone loss causes deformity, loss of height, pain, stiffness • Stooped posture • Loss of teeth