Histology #4 Hard Connective tissues

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  1. What is classified as a hard connective tissue?
    Bone, calcified cartilage, tendon and ligament
  2. Describe bones as an 'organ system', an 'organ' and a 'tissue'
    • organ system = skeleton (bones working together to form an organ system)
    • Organ = Bone- 1 element ie femur (cortex, medulla, marrow; diaphysis, metaphysis, epiphysis)
    • Tissue: Cells (osteocytes, osteoblasts, osteoclasts), ECM (collagen, proteoglycans (PGs), regulatory molecules; and hydroxyapatite mineral*****)
  3. Describe a bone as an organ (structure and function)
    • -Bony part (cortex)
    •  -cortical = compact bone
    •  -trabecular = cancellous = spongy bone
    • -attachments of muscle/ tendon/ ligament/ cartilages  
    • -vascular part = medulla
    •  -bone marrow: blood vessels, stem cells, stromal cells, megakaryocytes
    • -Mechanical support
    •  -attachment (muscle and tendon)
    •  -load-bearing (compression, tension, torsion)
    •  -protection
    • -Hematopoeisis (rbc formation)
    •  -marrow site of blood cell maturation
    • - Mineral reservoir
    •  -calcium and phosphorus metabolism
    •  -buffer
  4. Describe the 2 types of bone marrow (Red vs Yellow)
    • Red marrow (central)
    • -hematopoetic stem cells (produce rbc)
    • -mesenchymal stem stem cells (produce wbc)
    • -endothelial stem cells
    • -stromal/dendritic cells
    • -megakaryocytes
    • Yellow marrow (peripheral)
    • -stromal cells
    • -adipocytes
  5. Describe the structure, function, and histological structure of bone as a tissue
    • structure
    • -cells (~2)
    • -ECM (organic + inorganic)
    •  -collagen (type 1) ~30% of bone mass
    •  -hydroxyapatite ~ 70% of bone mass (Ca10 (PO4)6(OH)2)
    • function
    • -biomechanical
    • -mineral metabolism
    • histological structure
    • 1. woven bone
    •  -collagenous matrix "haphazard"
    •  -rapidly forming bone/ repair
    •  -weaker
    • 2. Lamellar bone
    •  -well organized -- layered collagenous fibers
    •  -mature
    •  -stronger
  6. What are the chief organic and inorganic components of bone
    • -ECM (~30%)=
    • collagen (type 1) ~30 % of bone mass
    • hydroxyapatite ~ 70% of bone mass: Ca, P, O, OH
  7. Describe the cell types of bone and their function*****
    • osteocyte: mature bone cells that maintains the bone matrix  (live in bone and connect to each other by gap junctions on their canaliculi*)
    • Osteoblast: immature bone cell that secretes organic components of matrix (so secretes ECM on surfaces)
    • Osteoprogenitor cell: Stem cell whose divisions produce osteoblasts
    • Osteoclast: Multinucleate cell that secretes acids and enzymes to dissolve bone matrix
  8. Recognise the hallmarks of BMU remodelling
    • BMU = bone multicellular unit
    • osteoclast-osteoblast-osteocyte complex responsible for bone remodelling (every 7-10 yrs whole skeleton is replaced)
    • bone remodelling occurs during growth and throughout adulthood
  9. What are the factors that influence bone health?
    • Hormonal/ Endocrine (PTH, calcitonin, E2)
    • nutritional (vitamins D, C)
    • Age
    • Mechanical (exercise, bed rest, spaceflight)
    • Disease (ie osteoporosis, metastases)
  10. Describe the events involved in endochondral and intramembranous ossification (ie bone histogenesis)
    • Bone grows ONLY by APPOSITION (on a suface):
    • -intramembranous model: fibro-vascular tissue scaffold (so mineral mineralizes on vascular tissue)
    • -endocondral model: Cartilage "anlage"

    Cartilage and fibrous tissue grows "interstitially" (so it grows by secretion of ECM)
  11. How does woven bone occur?
    during very rapid growth (histogenesis and injury) ie antlets
  12. Ellaborate on the endocondral ossification model of bone growth
    • Step 1: enlarging chondrocytes within calcifying matrix
    • Step 2: blood vessels grow around the edges of the cartilage and the cells of the perichondrium convert to osteoblasts. the shaft then becomes ensheathed in a superficial layer of bone
    • Step 3: Blood vessels penetrate the cartilage and invade the central region. fibroblasts migrating with the blood vessels differentiate into osteoblasts and begin producing spongy bone at a primary center of ossification. Bone formation then spreads along the shaft toward both ends
    • Step 4: Remodelling occurs as growth continues, creating a marrow cavity. The bone of the shaft becomes thicker and the cartilage near each epiphysis is replaced by shafts of bone. length and diameter increases with growth
  13. What are the zones on a growth plate?
    • Resting Zone
    • Zone of proliferation
    • Zone of hypertrophy
    • Zone of provisional calcification
    • "eating rat poison helps cause rapid death"
    • (epiphysis, resting, proliferation, hypertrophy, calcification, resorption, diaphysis)
  14. distinguish between bone and mineralized cartilage, tendon, ligament (on a slide)
    • So will go:
    • soft to hard tissue transition
    • tendon insertion
    • fibrocartilage
    • mineralization front
    • calcified fibrocartilage
  15. What is Wolff's Law of Bone******
    Bone adapts (remodels) to meet the mechanical demands placed on it
  16. Describe the connective tissue envelopes of bone
    • periosteum (covers bone)
    • endosteum (lines central canal)
  17. What is the basic structure and function of bone marrow?
    • Hematopoesis
    • so has hematopoietic and myelopoietic cells
    • megakaryocytes (multinucleated***)
    • adipocytes

    bone marrow = 4% of body mass
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Histology #4 Hard Connective tissues
2013-10-08 01:15:01

Histology #4 Hard Connective tissues
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