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Microscopic features of the Meniscus

- Discussion:
    - meniscal cells while typical chondrocytes, are called fibrochondrocytes because they synthesize fibrocartilage matrix, rather than hyaline 
             cartilage matrix typical of articular cartilage;
    - menisci are composed of circumferentially oriented collagen fibers, which are parallel to its peripheral border;
    - orientation of type I collagen fiber bundles is the major determinant of its stiffness (100-300 megapascals) and strength;
    - composed of collagen (98% type I), extracellular matrix includes proteoglycans, glycoproteins, and elastin;
             - chondrocitin sulfate is dominate glycoaminoglycoside in aggratating proteoglycan macromolecule;
    - interactions of extracellular matrix (water, proteoglycan, & collagen) account for behavior during compression, tension, & shear;
    - glycoaminoglycoside:
             - glycoaminoglycans of adult human consist of condroitin 6 sulfate (40%), chondroitin 4 sulfate (10-20%), dermatan sulfate (20-30%), and keratin sulfate (15%);

- Vascular Supply:
    - meniscus is vascularized in its prenatal development, however, w/ maturation blood supply extends on to peripheral 1/3;

- Innervation:
      - meniscus, unlike articular cartilage, does have within its substance sensory nerve endings;
      - type I and II nerve endings accompany this peripheral vascular supply;
      - in adults nerves occupy peripheral 1/3 of the meniscus;
    - central portion:
      - midsubstance of meniscus is avascular, aneural,
      - fibrochondrocytes are surrounded by an abundant extracellular matrix

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The innervation of the human meniscus.