Structure and Functions of Ligaments and Tendons

Composition of tendons and ligaments

Fibroblasts make up 20% and extracellular matrix makes up 80% - consists of elastin ground substance and collagen, tendons have more collagen than ligaments

Parts of tendon in order

Epitenon, endotenon, fascicle, fibre, fibril, microfibril, tropocollagen

Paratenon

Surrounds tendon and enhance gliding further interspersed between muscle cells

Enthesis

Where tendons inserts into the bone - important for reducing stress concentration on tendon and protecting collagen

1) fibrous enthesis = collagenous tendon or ligament directly attaches to bone

2) fibrocartilaginous enthesis = interface encompasses different transitional zones - uncalcified fibrocartilage, calcified fibrocartilage and bone

Collagen in tendons

Collagen fibres arranged parallel to each other, more collagen and less ground substance and water = stronger and more resistant to stretch (stiffer)

Collagen in ligaments

Less collagen and more ground substance and water = less stiff, slightly more elastin, orientation of fibres is more variable = function within a range of load directions

Function of ligaments

Connect bone to bone, augment mechanical stability in a joint, provide support in a primary direction, provide excessive motion in other directions

Function of tendons

Transmit forces developed in muscle tissue onto a bony lever to facilitate movement, would not be beneficial for a tendon to be flexible = less muscular force would be transmitted to the joint = less movement