Final.tendons Flashcards
Tenocytes contain and function
Tendon cells - well-developed RER
Synthesis and turnover of tendon fibres and ground substance.
Tenocytes are?
Sumerman like cells.
Quintescent cells
Elongated fibroblast like cells
Important - maintains tendon function
Tendon composition
Tenocytes 3% arranged in rows between col fibres
ECM - Col fibre - 65-85%
Elastic 1-2%
Ground substance
Tendon ground substance
GAGs, proteoglycans, glycoproteins 0.2-5%
Tendon hierarchical structure (5)
Arranged similar to muscle and nerve
Glycine, proline, hydroxy proline
Collagen fibre bundles surrounded by - CT
Only endo and epi tenon. CT
paratenon in fascia surrounding. 3rd. External layer - lct (fatty areolar)
Tendon ecm contains?
Collagen, pg and gags
Longitudinal and transverse collagen
Longi - 300um. Length. 1.5um height - triple stranded collagen molecule.
Transverse - 2 a2 and 1 a1 strands. Surrounded by pg and gsgs
Tendon strength dependent on?
Number, arrangement, position and size of collagen
Fibrillar organisation and thickness
Size on tendon depends on?
Collagen fibres
Largest tendon and has the?
Achilles
Largest collagen fibres
Ruture of tendon->
Decrease in collagen size
Tendon -> h and e -> LM
wavy morphology
Collagen strain - sirius red
Crimps - observe at em - wavy morph of coll fiber - due to planar undulations
tendon stretches, the muscle function with less change in length, allowing the muscle to generate greater force.
Tendon functions with,uscle
Crimps (3)
-Important stretch/stim by mechanotransduction
-Collagen fibres some flexibility - absence of hydroxyproline and proline specific location at aa sequence
Maintain homeostasis of tissue
Why tendon not completely elastic?
Lack of elastic fibres - greater amount of collagen
What is the crimp angle?
Tendon sinusoidal stretch curve.
Specific for each tendon
Ruptured tendon and crimp angle
Lower crimp angle
Tendon ecm (2)
Elastic fibres - recovery of waxy collagen fibre
Pg (4)
- bind water - mech stim - water moved from one compartment to another
- lubricate movement
- regulation of fibrillogenesis
- stabilisation of whole collagen system
Ligaments (2) difference between them and tendon fibres
Collagen fibres not completely parallel
Greater no. Of elastic fibres
Tendons, ligaments, fascia and each connections (3)
T muscle to bone
L bone to bone
F muscle to muscle
Tendon load deformation curve
Stress strain.
Physiological - 2%
Overuse - 5%
Rupture - 10
Toe, linear, partial failure, complete rupture
Tendon 3 sections
Myotendonous substances - inserted intoo deep recesses - formed by myocyte processes
Midsubstance - t1 (60%), t3-8, GAGS, glycoproteins, PGs
Osteotendinouus substance - same of mid + T2 collagen. Fibrouos ct, immineralised fibrocart, mineralised to cart bone
- Two Forms of Tendon Healing may occur:
Intrinsic - w/o blood flow - synovial fluid diffusion - no adhesion
Extrinsic - fibroblast proliferation - adhesion
Blood supply of tendons
Limited.
Via peritenon
Digits -> vinicula (folds of mesotenon penetrate tendon)
Tendoblasts and under pathological conditions ?
Active, rounded - proliferation (maintains normal homeostasis)
Pathological - increase in no.
Tenocytes (1)
Low rate proliferation
Collagen syn, degradation, mechanotranduction (actin), cell to cell occluding junctions.
Gap junctions, adheren junctions
Collagen turnover synthesis!
TGF B1 (cytokinin) -> LH
Collagen turnover - degradation
MMP pathway - mrna, prommp, mmp, active mmp -> col 1 + ecm degradation.
Timp inhibits mmp
Tissue inhibiting mellatoprotease
How does tgf b1 work?
Inhibitor of enzyme involved in col and ecm degradation
Tendon not static
When repetitive mechanical loading of tendon:
Cellular matrix response -> adequate -> adaptation.
Inadequate -> transient weakness in tendon -> if cont and exceeding tendon healing capacity -> overuse injury
Tendon stress deprivation (4)
Cells round up
Decrease in cell no.
Progressive disruption of collagen architecture
Apoptosis
Increase in mechanical load
Increase transcription and translation of collagen.
Decrease in mmp-1
Cerebral palsy
In cerebral palsy -> lengthening of tendon
Overuse of tendon
Increase in bv, rounded cells, lipid degeneration (accumulation of adipose tissue)
Low conc of mgcl2
Stain all pg and gags.
Relate activity of nucleus to mechanical load
Highest level of mmp?
No strain
Under stress deprivation?
Decrease chance of damage to tendon
Tenocyte ecm - cross link - actin cytoskeleton
- Interconnects ecm and neighbouring cells - mechanical coupling - info transported by integrins.
- Mod of gene expression
- imp for mechano transduction
Aged teno cytes
Not maintain good homeostasis.
Some cells - cytoskeleton depolymerises
Tenocyte primary cilium
Single cilium. Deformaion + bending -> cell response (3)
High mech loading - decrease on size.
Low mech loading - increase in size
Tenocytes - cilium - cell response (3)
Ca release
Activation of genes
Signalling molecules active
