Tendons And Ligaments

Question 1

Function of tendons and ligaments

Answer 1

• tendons attach muscle to bone
  
  • direct tendons have straight course between muscles and bone
  • wrap-around tendons bend around around a bony pulley
• ligaments attach bone to bone
  
  • guide and restrict motion of bones at joint

Question 2

The collagen helix structure

Answer 2

• type 1 collagen consists of three polypeptide chains wound around each other
• Coil itself is composed of coils which reverses its twist at higher structural level, giving tight structure and greater tensile strength

Question 3

Six-level collagen hierarchy

Answer 3

1. The collagen molecule
2. Five collagen molecules wind round in 3rd level helix to form microfibril
3. Microfibrils wound together to make subfibrils and fibrils - strength enhanced by cross linking
4. Fibrils pack together to form fibres
5. Fibres pack together into fascicles - undulating waviness
6. Tendons self assemble from fascicles

Question 4

Benefits of short vs long tendons

Answer 4

• a tendon must be stiff enough to transmit muscle forces without itself deforming a lot
• long tendons transmitting more variable forces as range of load extension curve increases
• long tendons reduce inertia effects

Question 5

Muscles and tendons being stretched

Answer 5

• as muscle stretches tendon becomes stiffer
• muscle also stiffens - if stiffer than tendon the muscle must contract to allow for fact that tendon is stretching

Question 6

Tendon and ligament failure

Answer 6

• tendons and ligaments are anisotropic because of directional fibres
• little resistance to bending and will fold under own weight
• deformation reversible in linear region
• continuing increase in stress levels causes breakage of collagen-collagen or collagen-elastin bonds - fracture
• ultimate strain to failure is about 35 percent

Question 7

Repair of ligaments and tendons

Answer 7

Tendons - torn tendons sewn together or to connective tissue
- tendon graft is rare
Ligaments