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12 Cards in this Set
- Front
- Back
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What is collagen and what is its function?
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A triple helix structural protein, which is the most abundant structural protein in the body.
It is the major component of ECM and structural foundation of all CT's. |
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How is type I collagen synthesized?
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1. translation of an amino acid triple sequence of hydroxyproline, proline and glycine forms an alpha chain (assembled in RER of fibroblast)
2. hydroxylation of proline and lysine residues (RER) REQUIRES VITAMIN C 3. 3 alpha chains form a triple helix to form PROCOLLAGEN (RER) 4. Procollagen is packaged in Golgi 5. Procollagen is released by exocytosis at the cell surface. 6. Procollagen peptidase cleaves procollagen to form TROPOCOLLAGEN (outside of fibroblast) 7. Tropocollagen molecules aggregate to form cross-striated collagen fibrils 8. Fibrils then assemble into bundles to from collagen fibres (See Netter's Histo p.57) |
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How many different types of collagen are there, and what determines the type of collagen?
Which cells produce collagen? |
1. up to 20
2. types of alpha chains in the helix 3. Osteoblasts, chondrocytes, fibroblasts |
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Describe type I collagen.
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Most abundant type of collagen composed of two alpha1 and one alpha2 chains.
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Which tissues contain type I collagen?
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- dermis
- ligaments - fascia - bone - **fibrocartilage - dentin - capsules of organs - sclera |
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Which tissues contain type II collagen
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- ***hyaline cartilage (articular surfaces, growth plate)
- vitreous body of eye |
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Describe the histology of fibrocartilage.
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- lacks a perichondrium
- matrix is very eosinophilic due to numerous type I collagen fibres - collagen fibres are arranged in parallel bundles in line with direction of mechanical stress - matrix contains ground substance which is seen at borders of lacunae and is basophilic -chondrocytes are thinly dispersed in the matrix -mixture of fibroblasts and chondrocytes are present (forms from dense CT in which some fibroblasts differentiate into chondrocytes) |
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Describe the histology of hyaline cartlage.
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- enclosed by a layer of dense CT (perichondrium) EXCEPT where it serves as articular cartilage and is exposed to synovial fluid
- chondrocytes are flattened near perichondrium and more round in deeper regions -chondrocytes often arranged in pairs of 4-6 -pair of chondrocytes = isogenous nest -matrix is composed of type II collagen, water, ground substance -collagen fibres - eosinophilic - GAGs - basophilic -territorial matrix surrounds isogenous nests and is basophilic - interterritorial matrix is between chondrocytes, is eosinophilic and containes basket-like network of type II collagen fibres |
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Cartilage only has one cell type. True or false?
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True. Chondrocytes are the only cells present in cartilage.
(Fibroblasts synthesize collagen outside of cartilage; can differentiate into chondrocytes) |
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How does the synthesis of type II collagen compare and contrast from that of type I?
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-composed of three IDENTICAL alpha chains (alpha1)
- also forms fibres (like type I)but are thinner and form a meshwork |
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How does the structure of type I collagen in bone differ from type I collagen found elsewhere?
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-has internal "hole zones"
-these holes provide space for deposition of hydroxyapatite crystals which will induce ECM mineralization |
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What is osteogenesis imperfecta?
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-hereditary disorder
-characterized by fragility, deformability and recurrent fractures of bone -results from abnormalities in type I collagen -requires lifelong management to prevent deformity and complications |
