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characteristics of CT

- specialized cells, protein fibers, ground substance
- embryonic, CT proper, specialized CT

embryonic CT

- made from mesoderm
- mesenchyme: spindle-shaped cells that interconnect via gap junctions, few reticular fibers
- mucous: in umbilical cord, dispersed cells, supportive network for arteries and blood vessels - decreases as gestation continues

CT proper

loose and dense

collagen fibers

- flexible but strong due to covalent bones between collagen molecules in adjacent rows
- glycine every 3rd AA to allow flexibility
- 3 alpha chains - 42 diff. alpha chains
- whole bunch of collagen with hydrogen bonding, here it is released into cove with ends that get cleaved
- packed into fibrils

types of collagen

- made of 3 alpha chains
- 42 types of alpha chains; 28 collagens characterized
- homotrimeric v heterotrimeric

fibrillar collagen

- I, II, III, V
- glycine, proline, hydroxyproline repeats

basement-membrane forming collagens

IV, VI, VII

fibrillar collagen biosynthesis

- make procollagen by translation/transcription
- need vitamin C for hydroxyproline of procollagen
- enzymes in cove cut C & N terminus - middle part makes the fibers

from fibrillar collagens to fibrils

- collagen fibrils assemble from many types of fibrillar collagens
- mature fibrils associate with other proteins that help link them to their environment

collagen synthesis v. degradation

- collagen molecules produced by fibroblasts, chondrocytes, osteoblasts, pericytes, epithelial cells
- growth factors stimulate collagen synthesis (TGF-B, PDGF) by fibroblasts
- steroid hormones inhibit synthesis of collagen
- degraded through proteolytic degradation and phagocytosis

reticular fibers

- type III collagen
- form branching patterns
- support cells of soft organs for framework
- early wound repair and replaced later by type I collagen fibers
- produced by fibroblasts, schwann cells, smooth muscle cells

elastic fibers

- thinner than collagen but branching
- composed of elastin and fibrillin - no collagen
- glycines randomly arranged so random kinks
- in blood vessels that expand and recoil
- bind covalently via desmosine and allysine (modified AA)
- fibrillin-1 microfibrils are substrates fro assembly of elastic fibers

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