Histology Cartilage

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Histology Cartilage
2011-10-15 22:55:41
Histology Cartilage

Photo quiz of histology cartilage
Show Answers:

  1. What is this?

  2. What is this?
    Elastic cartilage.
  3. Fibrocartilage
    • Hybrid of cartilage and dense connective tissue.
    • Resists compression and stretching.
    • Type I, ECM proteoglycans, Type II.
    • No perichondrium.

  4. What is this?
  5. Difference between cartilage growth types (2)?
    • Appositional growth: deposition of new matrix on surface of existing cartilage by chondroblasts.
    • Interstitial growth: division of chondrocytes within lacunae.
  6. What is the mineralized matrix in bone made up of?
    Mineral is calcium phosphate in form of hydroxyapatite crystals.
  7. Osteoprogenitor cells
    from mesenchymal stem cells found in the bone marrow. They differentiate into osteoblasts when triggered by core binding factor alpha-1 (CBFA1).
  8. Osteoblast
    • Young proliferative bone cells, secrete "osteiod" (type I collagen and bone matrix proteins).
    • Initiate mineralization with secretion of alkaline phosphatase into matrix.
  9. Osteocyte
    Adult bone cells maintain matrix in mature bone.
  10. What do osteoclasts do?
    • They function in bone resorption and remodeling.
    • Packed with lysosomes containing ACID phosphatase, which can break down bone.
  11. How does resorption happen?
    • 2 stage process.
    • 1. Matrix is decalcified by acidification of the bone surface through the release of protons which generate a pH of 4-5 in Howship's lacuna.
    • 2. Lysosome release hydrolytic enzymes which include cathepsin K and matrix metalloprotinases into the space resulting in degradation of collagen and other bone matrix proteins.
    • When resorption is completed, osteoclasts undergo apoptosis.
  12. What hormones affect osteoclast activity?
    • Parathyroid hormone (PTH) increases osteoclast activity raising the level of serum calcium.
    • Calcitonin (secreted by thyroid parafollicular cells) inhibit osteoclast activity.

  13. What is this?
  14. What is the relationship between proteoglycan content and mineralization in bone?
    It is a reciprocal relationship. Thus, proteoglycans can initiate and inhibit bone mineralization.
  15. What are canaliculi?
    Microscopic canals between the various lacunae of ossified bone.

  16. What things are shown here?
    • Osteon. Haversian system.
    • Volkmann (transverse) canal
  17. Osteogenesis
    • New bone formation:
    • osteoblasts make osteoid (type I collagen).
    • Loosely arranged collagen fibers is woven bone.
    • As bone matures, fibers compact and form lamellar bone. Strong, found in both cancellous and compact bone.
    • Formed via either intramembranous ossification or endochondral ossification.

  18. What process is shown above? Describe.
    • Intramembranous ossification.
    • At the right side, condensation of mesenchyme gives rise to osteogenic cells and osteoblasts. As osteoblasts enlarge and secrete more matrix (darker blue-green acidophilia toward left), they are seen to occupy the surface of the newly formed bone trabecula that extends across the center of this micrograph from left to middle right. A bone tissue surface has now been formed for appositional growth (the only mechanism for increased growth of bone tissue).
    • When matrix completely surrounds osteoblasts (far left), these cells differentiate into osteocytes, which are located within the bone matrix.
  19. Endochondral ossification
    In the development of the cartilage (endochondral) bones, models of hyaline cartilage are formed first. Specific areas within these models calcify and thus it is the calcified cartilage that provides the early surfaces for the appositional growth of bone tissue within these bone organs.
  20. Cancellous bone is AKA?
    Trabecular bone. Spongy bone.
  21. Main difference between trabecular bone formation and endochondral bone formation?
    No cartilage templates are involved in trabecular bone formation. In trabecular bone formation, the bone tissue is only composed of bone tissue matrix (mainly collagen), and not a combination of calcified cartilage and bone tissue as in the endochondral process.
  22. What is physes?
    Growth plate in endochondral bone formation.
  23. Endochondral bone formation: what happens?
    • Cartilage becomes calcified in diaphyseal region-chondroblasts differentiate into osteoblasts along the outside and form a collar of bone.
    • In the inner region- chondrocytes secrete alkaline phosphatase-mineralization of cartilage- calcified cartilage.
    • Blood vessels penetrate the outer boney collar. Periosteal cells accompany blood vessels and become osteoprogenitor cells, which become osteoblasts and form a primary ossification center.
    • Secondary ossification centers form at ends of long bones-physes; growth plates.
  24. Endochondral ossification, bones involved
    • Majority of bone organs in axial skeleton.
    • All of the bone organs in appendicular skeleton.
  25. zone of reserve cartilage
    chondrocytes in this region are inactive with no matrix proliferation.
  26. Zone of proliferating cartilage
    chondrocytes enlarge, start dividing and align in distinct cell columns.
  27. Zone of cartilage hypertrophy
    chondrocytes enlarged further, produce types I and X cartilage in addition to VEGF which initiates vascular invasion.
  28. Zone of calcified cartilage
    hypertrophied chondrocytes die by apoptosis as cartilage matrix becomes calcified.
  29. Zone of resorption
    Calcified cartilage is invaded by blood vessels resulting in parallel spicules of calcified cartilage. Osteoblasts attach to these spicules and begin depositing osteoid which become calcified to form bone.

  30. What is this?
    Endochondral bone growth.
  31. In the endochondral bone growth, what is responsible for the growth in length of long bones?
    Epiphyseal plate.

  32. What is this?
    • Osteocyte.
    • Multipolar cells that extend their fine cytoplasmic processes into canaliculi and "synapse" with adjacent osteocytes via gap junctions. Surrounding each osteocyte is a zone of unmineralized matrix consisting of collagen and ground substance, which allows for diffusion of gases, nutrients, from and to Haversian canal vasculature.
  33. Increase in width of bone in bone remodeling is due to?
    Increases in the width results from intramembranous ossification occurring at both the periosteal and endosteal regions.
  34. Where does bone formation occur in the diaphyseal region?
    On the periosteal surface.
  35. Why are haversian systems formed?
    • They form in pre-existing compact bone by internal remodeling via osteoclasts.
    • Form the resorption cavity.
  36. Articular cartilage
    • 2 distinct regions:
    • outer layer devoid of periosteum.
    • tidemark zone- thin irregular calcified cartilage linear region found b/n the calcified and non-calcified region of hyaline cartilage.
  37. Types of synovial cells
    • Type A: phagocytic
    • Type B: secrete synovial fluid