A and P Osseous tissue

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A and P Osseous tissue

  1. 1. Bone Histology and Movement Module #4
  2. 2. Characteristics of Bone TissueCalled Osseous tissueIs a type of connective tissueTwo types : 1. Compact – strength 2. Spongy – lighter weight
  3. 3. Characteristics of compact bone tissue:  Composed of: 1. Hydroxyapatite - ionic compound composed of calcium and phosphorus. Ca10(PO4)6(OH)2 2. Ground substance (water and other proteins) 3. Collagen
  4. 4. The characteristics of compact bone:  Hydroxyapatite and other minerals give bone its hardness and compressive strength Collagen (protein) fibers give bone its flexibility.
  5. 5. Compact bone - Functional unitcalled an osteon. Osteon
  6. 6. Osseous Tissue Bone contains 4 types of cells: 1. Osteogenic 2. Osteoblasts 3. Osteocytes 4. Osteoclasts
  7. 7. 1. Osteogenic cells Osteogenic cells are stem cells that divide to produce osteoblasts. Assist in repairing bone fractures. Overproduction causes osteogenic sarcoma (cancer).
  8. 8. Osteogenic Sarcoma
  9. 9. 2. Osteoblast cells Osteoblasts are immature bone cells that secrete the matrix When osteoblasts are surrounded by bone, they mature and become osteocytes.
  10. 10. 3. Osteocyte cells Osteocytes are mature bone cells that maintain the bone matrix. Each osteocyte lives in a lacuna. Canaliculithrough the lamellae allow osteocytes to obtain necessary nutrients.
  11. 11. 3. Osteocyte cells continued Osteocytes do not divide. The main functions of osteocytes are: 1. to maintain the protein and mineral content of the matrix. 2. to help repair damaged bone.
  12. 12. Osteocyte Osteocyte
  13. 13. 4. Osteoclast cells Osteoclasts are very large cells that remodel bone.(break down old bone)Note: Bone building and bone recycling must be kept in balance. When osteoclasts break down bone faster than osteocytes build bone, bones become weak.
  14. 14. Osteoclast Osteoclast
  15. 15. Note: Wolffslaw : Bones get stronger with exercise, stress causes osteocytes to build more bone. Bone remodeling: Bone is broken down because it deteriorates over time and must be replaced. Also minerals are released that the body needs.
  16. 16. Osseous Tissue
  17. 17. Structure of compact bone Osteon –basic unit. Osteocytes are arranged inconcentric circles (concentric lamella)around a central canal called theHaversian canalwhich contains theblood vessels.
  18. 18. Structure of compact bone  Connecting the central canal is the perforating canals called the canaliculi carry nutrients to the osteocytes  Lacunae – spaces in the rings where osteocytes are found
  19. 19. Structure of compact bone In between the osteons is interstitial lamellae or “packing material”
  20. 20. Structure of compact bone:Circumferential lamallae - A bonylayer that underlies the periosteumor endosteum.
  21. 21. Structure of compact bone Perforating canal – canals in the bone that blood vessels pass sideways between Haversian canals
  22. 22. Structure of compact bone All osteons in long bones run the length of the bone, strengthening the bone in that direction.
  23. 23. Structure of compact bone All osteons in long bones run the length of the bone, strengthening the bone in that direction.
  24. 24. Spongy boneFound in the center of bones and on the endsLight weight
  25. 25. Structure of spongy boneSpongy bone does not have osteons. Its matrix forms an open network of trabeculae.
  26. 26. Structure of spongy bone no blood vessels Spacesare filled with red bone marrow which has blood vessels and supplies nutrients to the osteocytes.
  27. 27. Structure of spongy bone Red bone marrow is red because it forms red blood cells. In other bones, spongy bone may hold yellow bone marrow, which is yellow because it stores fat.
  28. 28. Bone formation Human bones grow until about age 25. The process of replacing cartilage tissue with bone is called ossification.
  29. 29. Growth in length of long boneEpiphyseal plate is the site ofgrowth in the long bone. Locatedbetween epiphysis and diaphysis.Epiphyseal plate is composed ofhyaline cartilage with chondrocytes(reproductive).
  30. 30. Growth in long bone:1.At epiphyseal plate chondrocyteswill reproduce.2.New chondrocytes are laid down onthe epiphysis end of bone3.Old chondrocytes on the diaphysisend will elongate the lacunae.4.Calcium salts will be laid downaround elongated lacunae.5.Chondrocyte is cut off from nutrientsand will die.
  31. 31. Growth in long bone:6.Blood vessels will grow in lacunaeof dead chondrocytes and bringosteoblasts.7.Osteoblasts will produce andmaintain bone matrix and mature toosteocytes.8.Therefore, spongy bone will ofepiphysis is remodeled into compactbone and diaphysis increases inlength.
  32. 32. Growth in long boneNOTE: Epiphysis can grow in thesame way except from the articularcartilage at the end of bone.
  33. 33. Growth in long bone Appositional bone growth – growth in width of the bone.Osteoblast lay down new matrixon top of old matrix expanding diameter.
  34. 34. Bone RemodelingOld bone broken down by osteoclastand rebuilt by osteoblast.Reasons:1.Change spongy bone to compact2.Increase/decease mass of bones3.Repair damaged4.Replace worn out collagen
  35. 35. Bone RemodelingHow:Osteoclasts secrete acids andproteolytic enzymes that break downand dissolve bone salts and digestproteins (collagen).Osteoblast brought in by damagedblood vessels to lay down newmatrix.
  36. 36. Diseases of the bone:1. Rickets – low calcium andphosphorous levels in the bloodleading to a lack of hydroxyapatite inthe bones resulting in the bonesbecoming rubbery.Cause: lack of Vitamin D in thediet which regulates Ca and P
  37. 37. Diseases of the bone:2. Brittle Bone Disease Osteogenesis imperfecta –Result of decreased amount ofcollagen making the bones brittle.Cause – genetic
  38. 38. FracturesFractures are repaired in 4 steps: Step 1. Hematoma forms Bleeding produces a clot called the fracture hematoma Bone cells in the area die.
  39. 39. Fractures Fractures are repaired in 4 steps: Step 2. Callus forms A callus (mass of tissue that connects the ends of broken bone) is formed. Internal callus forms new bone tissue and is found between the breaks External callus stabilizes the bone while it begins to heal and is found around the outside of the bone
  40. 40. FracturesFractures are repaired in 4 steps: Step 3 Callus is ossified Osteoblasts replace the central cartilage of the external callus with spongy bone.
  41. 41. FracturesFractures are repaired in 4 steps: Step 4. External callus removed and remodeled Osteoblasts and osteocytes continue to remodel the fracture for up to a year, reducing the bone calluses.

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