Pathology
Collagen
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Get access- Most common protein in animals
- Extracellular framework for all multicellular organisms
- Produced by fibroblasts
Basic unit is three polypeptide chains in a left-handed helix: regular triple helix (procollagen also contains a triple helix)
- 2 alpha-1 chains
- 1 alpha-2 chain
- Types I-III are interstitial or fibrillar collagen
- Type I accounts for 80% of collagen in skin and 90% in bone
- Types IV-XI appear as amorphous material in interstitial tissue or basement membranes
Note
Vitamin C (ascorbic acid) is an important cofactor for collagen synthesis
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Collagen types by ocular tissues
| Tissue | Collagen type |
| Iris stroma | Types I and III |
| Sclera | Predominantly type I |
| Epithelium-Bowman’s hemidesmosomes | Type VII |
| Bowman’s layer | Type I, III, V and VI |
| Corneal stroma | Type I (70%). Types IV, V and VII are also present |
| Descemet’s membrane | Type IV |
| Lens capsule | Type IV |
| Vitreous | Types II, IX, V/XI, VI also present |
| Choroid | Type III (loose matrix around vessels) |