Lecture 17 - Tissue engineering: understanding tissue mechanics Flashcards
in vivo stress/strain histories need to be measured to understand how..
the native tissue acts in the body
What can be used to test the strength of bone
Quasi static tensile/compression tests conducted using instron micro-tester
Human tissues usually have what property?
viscoelasticity - like blu tac
Anisotropic - direction of load gives different stretch properties
What are some of the loading modes that engineered tissues need to mimick?
tension
compression
shear
Cancellous bone fractures…
abruptly under tension, showing a brittle material behavior
Energy absorption of cancellous bone is..
higher under compressive force than under tensile
What are the two main fibres found in connective tissue?
Collagenos fibres (Collagen) - unbranched, colourless fibres that are usually deposited in bundles to form wavy, parallel groups
elastic fibres - branching, yellowish - deposited singly and stretch readily under tension. Straight individual fibres
what are the collagan/elastin percentages for tendon, ligament, skin?
Skin
Elastin 2%, Collagen 71%
ligament
Elasin 75%, collagen 17%
Tendon
Elastin 4.4%, collagen 86%
Collagenous fibres are ____than elastic ones and can withstand far ______ tension before they break
Collagenous fibres are stronger than elastic ones and can withstand far greater tension before they break
IN tendon, the collagen are orientated in alignment with the _____ ________that the tendon undergoes physiologically, whereas skin in a relaxed state has fibres that are ….
IN tendon, the collagen are orientated in alignment with the tensile stresses that the tendon undergoes physiologically, whereas skin in a relaxed state has fibres that are not in any order
The morphology is also important
What is Pre-stress? (tension, cleavage lines)
loaded stress in skin - surgeons should cut along Langers line so the wound doesn’t open up
