low activity for maintaing fibers and ground substance of ECM
Stimulated to become active (fibroblast) upon injury or tissue damage (or wound healing)
What is a fibroblast?
intense synthetic activity for collagen and ground substance molecules
What are 4 types of ECM molecules?
What is collagen?
main fiber of the ECM
family of proteins developed to acquire varying degrees of rigidity, elasticity, and strength
Resist tensile forces to provide strength to tissues
Most abundant in the human body (30% of dry weight)
25 different types classified into groups
What are the 4 groups collagen is classified as?
Collagen that forms fibrils
Collagen that forms anchoring fibrils
Collagen that forms networks
What are the 4 types of collagen, their synthesis (s) , location (l), and function (f)?
Type I - (s) fibroblasts and osteoblasts, (l)bone, tendon, and ligaments, (f) resist tension
Type II - (s) chondroblasts, (l) cartilage, (f) resist compressive and shear forces at surface
Type III - (s) fibroblast, (l) pliable tissues ex: blood vessels, uterus, GI tract, skin, muscle, (f) structural maintenance in expandable organs; initial collagen of would repair
Type IV - (s) fibroblast, (l) basement membrane ex: muscles cells, epithelial cells, adipocytes, (f) support of delicate structures, filtration
What is the protein unit that polymerizes to form collagen fibrils?
Tropocollagen - a 3 subunit polypeptide chain intertwined in a triple helix
What are the 3 collagen molecules?
What are some examples of defects in collagen synthesis?
Ehlers-Danlos (type IV)
Describe CT proper reticular fibers and its function.
Composed of Type II collagen fibers
very thin, small, and loosely packed
fibers are bound together to ECM with abundant interfibrillar bridges with PGs and glycoproteins
Fxn: provide framework for organs (lymph nodes, spleen, bone marrow, liver)
Describe CT Proper elastin fibers.
provide resilience (allows stretching) to the tissue
rich in protein elastin
rubber-like qualities (5x's more extensible)
Amino acids (desmosine and isodesmosine) provide covalent bonds that form cross-links between elastin fibers
What are elastic fibers synthesized by, their location, and main function?
(s) fibroblasts; smooth muscle cells
(l) pliable tissue (blood vessel, uterus)
(f) elongation without deformation
What happens to the elastic fibers as a person ages?
they get replaced by Type I collagen which doesn't allow as much elasticity
What is Marfan Syndrome?
a genetic mutation disrupting proper elastin fiber synthesis
creates non-compliant brittle tissue, especially the arteries, that are prone to rupture
What are proteoglycans?
filamentous protein core with attached GAGs
provide framework for ECM
What are glycoproteins?
proteins bound to small carbohydrate molecules
provide framework for ECM
What is the function of CT proper ground substance?
fills spaces between cells and gibers of CT and provides a pathway for waste and nutrient exchange
Fluid provides for lubrication of ECM
Provides a barrier to penetration of foreign (infectious) agents
Describe CT proper tissue fluid.
plasma protein, ions, diffusible substances (nutrients and wastes)
GAGs bind to water of ECM to maintain hydration of tissue
What is a tendon?
Dense Regular CT
collection of collagen fiber bundles
the bundles are enveloped by loose CT containing blood vessels and nerves
Externally surrounded by a sheath dense CT
?What is a tendons function, innervation, and nutrient supply?
FXN: connect muscle to bone and transmit mechanical force generated by muscle to bone to create joint movement
Innervated by GTO and pain fibers (fee nerve endings)
Has limited vascular supply but gets nutrition from synovial membrane (tendon sheath)
What is a synovial sheath and its function?
Dense irregular CT
has 2 layers: visceral layer and parietal layer
Between the layers is a cavity filled with fluid
FXN: provide lubrication for tendons to slide within their fibrous sheath
What are some CT proper changes with acute activity?
increase in temperature and increase in elasticity
micro tears occur, are then repaired stronger and larger
Prevention of cross-links to maintain extensibility
When would stretching by most beneficial - before or after exercise?
What are CT proper changes with chronic activity?
hypertrophy allows the CT to transmit increased amount of force
increase deposition of type I collagen
increase load to failure
increase ROM if stretched
What is the function, innervation, and nutrient supply of ligaments?
Dense Regular CT
FXN: connects bone to bone, controls and guides normal movement of joints, limits excess motion, and contain more elastic than tendons
Innervation: proprioceptive fibers and free nerve endings
Nutrient: limited vasculature
What are some CT proper changes with aging for Loose, Dense Reg, and Dense Irreg CT?
-Loose CT - decrease in elasticity and hydrophilic capabilities (dried out) with causes a decrease in ROM, and increase in work to overcome inelasticity
-Dense Reg - decrease in elasticity and hydrophilic capabilities (dried out) with causes a decrease in ROM, and increase in work to overcome inelasticity
-Dense Irr - decrease in size and protein synthesis which causes a decrease in tensile force, decrease in load to failure, and fiber degradation
What are some CT changes with immobilization?
for tendons and ligaments: decrease in tensile force generation and decrease load to failure, decrease GAGs and H2O, cross linking of collagen which reduces compliance and synovial sheath becomes adherent on tendons which cause adhesions and those prevent full ROM