12 terms

Histology Ch. 6

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
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