3 different fiber types and matrix composition (review)
collagen, elastin, reticular fibers and ground substance/tissue fluid
fibrocyte
quiescent cell that maintains low activity level in maintaining fibers/ground substance. Can be stimulated to become a fibrocyte in response to injury etc.
fibroblast
undergoes intense synthetic activity of fibers/ground substance (large RER and lots of golgi)
ECM molecules (4 types)
collagen, elastin, proteoglycans (of which glycosaminoglycans are a component of), glycoproteins
definition of collagen
family of proteins developed to give varying degrees of rigidity, elasticity, and strength. (over 25 types)
proportion of collagen
most abundant protein of human body (about 30% of dry weight)
type 1 collagen - synthesis, location, function
it is synthesized by fibroblasts, osteoblasts. Located in bones, tendons, ligaments. Main function is to resist tensile force
type 2 collagen synthesis, location, function
synthesized in chondroblast. Located in articular processes and fibrocartilage (cartilage in general) Function - resists compressive and shear forces at surface
type 3 collagen synthesis, location, function
synthesized by fibroblast. found in artery walls, intestinal walls, uterus, skin, bladder. Function is to accomodate shifts in volume of spaces it encloses and initial collagen of wound repair
type 4 collagen synthesis, location, function
synthesized by fibroblast, located in basement membranes, supports delicate structures and allows filtration.
What is tropocollagen? how does it relate to collagen differentiation?
3 subunit polypeptide chains intertwined into a triple helix. Differences in chemical composition of tropocollagen account for types of collagen
out of four main types, which collagen forms fibrils? fibers? fiber bundles?
types I, II, III form fibrils. Types I and III form fibers. Type I forms fiber bundles. Type IV does not form any of these
describe type I collagen synthesis
preprocollagen in RER > (Vit C) > Procollagen in Golgi > exocytosis to ECM > procollagen peptidase > tropocollagen
what is the defect and symptoms of Ehlers-Danlos type VII
a decrease in procollagen peptidase production. increased articular mobility, increased subluxation (partial displacement of a joint)
defect and symptoms of scurvy
cannot convert preprocollagen to procollagen (no Vit C), ulceration of gums, hemorrhages, weak bones
describe defects and symptoms of osteogenesis imperfecta
congenital malformation of type I collagen production, spontaneous fractures and cardiac insufficiency
defects and symptoms of keloid scarring
hyper-production of collagen, local swelling that forms in scars of skin
type III reticular collagen configuration
spaced fibers with abundant proteoglycans and glycoproteins to allow for volume changes. Fibers provide frame work for organs (liver, spleen, lymph nodes, bone marrow)
Elastic fibers
rich in protein elastin. Remember oxytalan, eulanin, elastin configuration. 5x more extensible than rubber. Desmosine and isodesmosine provide bonds of cross links between elastin fibers
elastic fibers: synthesis, location, function
fibroblasts and smooth muscle cells. pliable tissue and blood vessels, uterus, etc. elongation without deformation
elastin with age
replaced by type 1 collagen, elasticity loss.
what is Marfan syndrome
disruption of elastin fiber synthesis. Brittle structures that should be pliable, prone to rupture.
ground substance function and composition
nutrient/waste exchange, lubrication of ECM, Barrier to penetration of foreign agents. Lots of proteoglycans/glycoproteins (fibronectin, laminin)
tissue fluid of ECM
plasma proteins, ions, diffusible substance (nutrients and waste). similar to plasma of blood.
GAGS bind to _____ to maintain hydration of tissue
water
go back and study tables in CT proper powerpoint! slides 18, 19, 20
