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- See:
      - Disorders
      - Ligament Healing Characteristics:

- Discussion:
    - collagen is the primary structural protein of the body & occurs in bone, tendon, and scar tissue as well as in cartilage;
    - at least nineteen distinct gene products have been identified in humans, for different types of collagen, that differ by amino acid
           structure of alpha chains;
    - their composition differs slightly in different species, but its general function is the same in all;
    - biosynthesis of collagen
    - type I collagen: bone, tendon, skin, menisci
    - type II collagen:
            - fibrils of type II collagen account for > 50 % of dry wt of cartilage;
            - Examples: Articular cartilage and Nucleus pulposus of intervertebral disc
            - type II collagen is also found in small amounts in the vitreous gel and in a number of other tissues during early development;
            - examples of type II collagen disorders:
                   - achondrogenesis
                   - SED
    - type III collagen:
            - type III collagen is found in small amounts in many tissues in association w/ type I collagen & is major component of large
                      blood vessels; skin
    - type IV collagen, one of the nonfibrillar collagens, is a major constituent of all basement membranes;
    - type V and VI collagen
            - articular cartilage (small amounts)
            - type V Collagen .  .J. Leeming, M.A. Karsdal, in Biochemistry of Collagens, Laminins and Elastin, 2016
            - Features Suggesting a Skeletal Tissue Disorder Versus JIA WG. Cole, O Mäkitie, in Textbook of Pediatric Rheumatology, 2016
            - Ehlers–Danlos Syndrome Peter H. Byers, in Emery and Rimoin's Principles and Practice of Medical Genetics, 2013
            - Ehlers–Danlos Syndrome Salahuddin Kazi, in Encyclopedia of Gastroenterology, 2004
    - type VII and VIII collagen, epithelial basement membranes
    - type IX collagen:
            - these molecules surround the surface of the type-II collagen fibrils and covalently cross-linked to them;
            - these molecules may mediates the interaction of type-II collagen with surroundingr extracellular matrix components;
            - MED
    - type X collagen production:
            - short-chain collagen found only in the hypertrophic zone;
            - mutations here may cause Schmid metaphyseal chondrodysplasia;
            - associated with matrix mineralization (calcification)
    - type XI, also articular cartilage,
    - type XII, tendon

- Microscopic Characteristics:
    - in different tissues, size of the collagen fibers varies markedly;
    - as measured by light microscopy, diameter of tendon fiber may be several hundred microns, whereas in loose connective tissue it
            may be only 1;
    - w/ the electron microscope, finer fibers called fibrils vary from 20 nm to less to 50 or 60 nm;
    - arrangement of these fibrils and their size characterize different tissues

Development of a reconstituted collagen tendon prosthesis. A preliminary implantation study.

Identification of novel pro-alpha2(IX) collagen gene mutations in two families with distinctive oligo-epiphyseal forms of multiple epiphyseal dysplasia.

Stickler syndrome without eye involvement is caused by mutations in COL11A2, the gene encoding the alpha2(XI) chain of type XI collagen.

A type X collagen mutation causes Schmid metaphyseal chondrodysplasia.