CT proper and cartilage 2

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CT proper and cartilage 2
2010-08-17 14:28:48
collagen dense CT reticular CT elastic CT

part 2 of CT lecture
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  1. collagen
    90% is type 1 collagen with high tensile strength and high flexibility

    TEM: fibrils look banded, and fibers look like collections of fibrils

    LM: red or pink stain with eosin in H/E and look wavy and unbranched
  2. Production of collagen
    Fibroblasts -> procollagen (triplet polypeptide chain) rich in hydroxyproline and hydroxylysine

    -procollagen secreted by exocytosis to extracellular space, peptidases cleave terminal ends of molec to form tropocollagen

    tropocollagen self-assembles into fibrils which become fibers
  3. other collagens
    type 2 and 3 collagen are other types of fibrillar collagen

    type 4 collagen is nonfibrillar collagen in the basal lamina
  4. Elastic fibers
    composed of elastin rich in desmosine and isodesmosine, fibrillin, and other glycoproteins

    -has little hydroxyproline and no hydroxylysine

    -elastin = gives elasticity, fibrillin acts as structural and organizing element, desmosine and isodesmosine bind adjacent elastin molec together to allow stretch and recoil
  5. Elastic fiber stains
    orcein - dark brown

    resorcin- fuchsin: purple/black

    aldehyde fuchsin - purple

    verhoeff's stain - black
  6. Dense CT
    dominated by type 1 collagen made by fibroblasts with fewer cells than loose CT

    -mechanically links other tissues or supports other tissues
  7. Dense CT ECM
    major tissue component = fibrous with little ground substance

    fibroblasts = elongated

    some elastic fibers produced but less than collagen
  8. Dense regular CT
    • location: tendons/ligs
    • -Type 1 collagen fibers = aligned to run in same direction

    tissue = poorly vascularized and appears white
  9. Dense irreg CT
    location: dermis of skin and organ capsules

    layers of collagen, each layer has fibers in same dir but oblique to other layers
  10. Scurvy
    vitamin C deficiency leads to reduced collagen 1 synthesis (dense irreg CT)

    common in periodontal lig anchoring teeth in bone sockets -> loose teeth
  11. reticular CT composition and functions
    composition: type 3 collagen fibers

    • functions: delicate framework to allow cells and fluid to move within an organ
    • -supports blood vessel walls and forms supporting network around fat cells/nerve fibers/ and skeletal and
    • smooth musc fibers
  12. Reticular CT location
    1) forms stroma of bone marrow, liver, and lymphatic organs except thymus

    2) associated with basal lamina of epithelia, around blood vessels, muscles, nerve fibers, in loose and dense CT and around adipose cells
  13. Reticular fibers
    type 3 collagen produced by reticular cells in lymph. organs by same method as type 1 collagen by fibroblasts

    fibrils form small, delicate bundles (string bag) to organize tissue of organs while allowing interchange of cells/fluid

    TEM: type 3 fibers look like type 1 but very thin

    LM: stained by silver salts, fibers = thin and highly branched

    -type 3 collagen also stained by periodic acid schiff technique for carbs
  14. Ehlers-Danlos Type 4 Syndrome
    insufficient synthesis of type 3 collagen (prominent in aorta and intestines) can lead to rupture
  15. Elastic CT
    this CT domintaed by elastic fibers to provide stretch and elasticity

    components: fibroblasts or smooth musc cells dominate, ECM is dominated by elastic fibers

    Fiber organization: elastic fibers as loose branching, bundled network, or fenestrated laminae or lamellae (sheets with holes)
  16. recognizing elastic CT
    mixed with loose and dense irreg CT in skin (long, thin, branching fibers)

    must use special stains for elastin fibers

    in vessels- one or more thin layers in in arteries and large veins
  17. Marfan's syndrome
    for elastic CT

    mutations in gene for microfibrillar component affects large blood vessels.

    normally thick aortic wall gets thin and can rupture
  18. Adipose CT
    well vascularized and dominant cell = unilocular adipocyte

    ECM: reticular fibers secreted by adipocytes with little ground substance
  19. defects in leptin pathway
    in adipose CT

    adipose tissue secretes leptin that goes to hypothalamus where it regulates food intake and metabolism

    problems in pathway may lead to obesity