Tendons & Ligaments Flashcards
Function of tendon
Connect muscle to bone
Transmit tensile forces from muscle to bone to allow movement
Function of ligaments
Connect bone to bone
Stabilises joints so prevents excessive movement
Proprioceptive function
What is the cellular component of tendons & ligaments
Fibroblasts (tenocytes in tendons) - synthesise ECM & collagen
What type of collagens are found in tendons and ligaments
Type 1 & 3
Difference between structure of tendons & ligaments (4)
More collagen in tendons
Less elastin in tendons
Less ground substance in tendons
Tendons have predominantly Type 1 and trace Type 3
Why do tendons have little/negligible elastin
They need to transmit tensile forces to bone
Stretching tendons would waste energy
Components of ligaments & tendons
Water
Collagen types 1 & 3
Ground substance (matrix of GAG, PGs and other ECM components)
Elastin
How are collagen fibres arranged in tendons and why
the large fibres are regularly arranged in PARALLEL
tendons transmit UNIDIRECTIONAL force from muscle
How are collagen fibres arranged in ligaments and why
smaller diameter fibres are arranged randomly
ligaments can be loaded in many directions depending on movement
What does the endotenon do?
Thin sheet of connective tissue what wraps around fibrils & fascicles
permits some longitudinal movement of the bundles relative to each other
Contains vessels, lymphatics & nerve supply
What does the epitenon do?
Wraps around bundles of fascicles
Contains vessels, lymphatics & nerve supply
Produces synovial fluid, reducing friction between itself and paratenon
What does the paratenon do?
The outermost layer of tendon
Nerves and blood vessels run through it
Allows tendons to glide freely
What are vascular tendons?
Tendons that are surrounded by paratenon
They have rich blood supply
They don’t wrap around structure
What are avascular tendons?
Tendons that are surrounded by a synovial sheath
Less vascularised
Receive nutrients via diffusion from synovial fluid
Wrap around joints
describe Direct Insertion into bone
Superficial fibres join the periosteum
Deeper fibres transition from tendon/ligament –> fibrocartilage –> mineralised fibrocartilage –> bone
describe Indirect insertion into bone
Superficial fibres join the periosteum
Deep fibres insert directly into bone via perforating (mineralised) collagen fibres
How are ligaments supplied with blood
Receive nutrition via Micro-vessels at the insertion site
Explain the process of fibre recruitment
Fibres across the length have varying stiffnesses
When loaded different fibres experience different strains
As magnitude of applied force increases, stiffer fibres are recruited
This is non-linear elastic behaviour
What is the toe region in the force-extension curve
An area where significant deformation is seen for small stresses
There is straightening out of crimped collagen fibres and re-orientation in the direction of loading
Why is failure unpredictable
fibres have different stiffnesses
Material vs Structural properties
Material properties look at things like Ultimate stress/strain, Young’s modulus and is independent of geometric properties of the object
Structural properties focus on the geometry of the specific object
Mechanics of tendons v ligament
Tendon have greater ultimate tensile strength and strain
Tendons have greater (linear) Youngs Modulus
Why is okay that ligaments are less stiff
Their function is the support movement of joints
Too much stiffness would limit motion
Compare toe regions of tendons and ligaments
Tendons experience larger forces so recruit fibres more quickly –> shorter toe region
Ligaments experience less force so recruits fibres gradually –> longer toe region
