Week 3: Tendons

histology of tendon

dense, parallel fibers, connective tissue

tendons are bundles of

course collagen fibers along scattered rows of fibroblasts with elongated nuclei

endotenon has what collagen

collagen type III

epitenon has what collagen

collagen type I

peritenon (tenosynovium)

areolar tissue becomes tendon sheath in some areas

behavior of tendon is determined by

amounts, types, organization of extracellular components

collagen (type I) is what percent of tendon

65-75% of dry weight

elastin is what percent of tendon

2%

matrix is composed of

proteoglycans (water)

cell types

tenoblasts, tenocytes

what is the primary site of force transmission

musculotendinous junction

4 main functions of tendon

transmit force between muscles/bones, store elastic energy when stretched, connect bone to muscle, concentrate pull of muscle in smalla rea

resting position of tendno

slightly crimped (toe region of load-deformation curve)

what causes the force that a tendon can withstand?

cross sectional area, composition, length of tendon

effects of aging on tendon

repair is delayed

why is repair delayed

reduction of enzymes necessary for formation of collagen

what composition changes with age

tropocollagen and ECM

with aging, there is an increase with

cross linking of tropocollagen which causes collagen to become stiffer and more brittle, more likely to tear

3 effects of inactivty/immobility on tendons

decreased collagen synthesis, atrophy of tendon, weaker due to structural changes

strength exercise effects on tendon

increased cross sectional area, strength, collagen content

strength is best for

power, strength, injury prevention

endurance exercise effects on tendon

minimal change in cross sectional area and strength, same/decreaed collagen content

endurance exercise is best for

endurance and repetitive motion efficiency

5 effects of diabetes/smoking/HTN on tendons

thickened, disorganized collagen, calcific changes, less fibroblast proliferation and lymphocytes infiltration, reduced elasticity (increased hysteresis)

inflammatory stage of healing

within first 3 days of injury

repair stage of healing

seen within one week

-formed at random, fibroblasts predominate, collagen content increases through first 4 weeks, oriented perp to gap

remodeling stage of healing

begins within 2 months of injury

complete healing occurs when

tensile load strength returns

do tendons regenerate like muscle?

no, it repairs with scar tissue

progression of tendon injuries

inflammation is minimal/absent, gradual changes of tendon tissue, pain occurs eventually (may be due to revascularization/growth)

some tendons rupture without any

previous signs/symptoms

4 clinical and functional classifications of tendon injury (4 stages)

1)pain after sports activity

2)pain at beginning of sports, decreases with warmup and returns with fatigue

3)pain at rest and with activity

4)rupture