Final.tendons Flashcards by naynesh patel

Tenocytes contain and function

Tendon cells - well-developed RER

Synthesis and turnover of tendon fibres and ground substance.

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Tenocytes are?

Sumerman like cells.
Quintescent cells
Elongated fibroblast like cells
Important - maintains tendon function

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Tendon composition

Tenocytes 3% arranged in rows between col fibres
ECM - Col fibre - 65-85%
Elastic 1-2%
Ground substance

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Tendon ground substance

GAGs, proteoglycans, glycoproteins 0.2-5%

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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)

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Tendon ecm contains?

Collagen, pg and gags

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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

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Tendon strength dependent on?

Number, arrangement, position and size of collagen

Fibrillar organisation and thickness

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Size on tendon depends on?

Collagen fibres

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Largest tendon and has the?

Achilles

Largest collagen fibres

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Ruture of tendon->

Decrease in collagen size

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Tendon -> h and e -> LM

wavy morphology
Collagen strain - sirius red
Crimps - observe at em - wavy morph of coll fiber - due to planar undulations

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tendon stretches, the muscle function with less change in length, allowing the muscle to generate greater force.

Tendon functions with,uscle

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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

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Why tendon not completely elastic?

Lack of elastic fibres - greater amount of collagen

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What is the crimp angle?

Tendon sinusoidal stretch curve.

Specific for each tendon

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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