Tendon & Ligament Flashcards
Ligaments join ___ to ____
Ligaments join BONE to BONE
Tendons join ____ to _____
Tendons join MUSCLE to BONE
Choose the TWO correct functions of tendons:
- Elastic energy storage and release
- Protect the muscle tissue
- Transmit muscular forces
Tendon functions:
- Elastic energy storage and release
- Transmit muscular forces
What is the main function of ligaments?
Restrain joints
What is the main type of collagen found in ligaments and tendons?
Type I collagen
What is the name of the connective tissue surrounding each tendon fascicle?
The endotenon (also known as the endotendineum). This is the connective tissue WITHIN the tendon, surrounding each bundle of fibres (fascicles).
The specialised elongated fibroblast-like cells found in tendons are called…?
Tenocytes
Put these in order of hierarchy from the largest to smallest unit:
Collagen fibre Collagen molecule
Whole tendon Fascicle
Collagen fibril
Hierarchy, largest to smallest: 1 - Whole tendon 2 - Fascicle (bundle of collagen fibres) 3 - Collagen fibre 4 - Collagen fibril 5 - Collagen molecule
What is the composition of tendon/ligament? HINT: there are THREE main substances. Give proportions too!
60-70% water
25-30% collagen type I
0.3% glycosaminoglycans
What is crimp? What role does it play in the function of tendon/ligament?
Crimp is the WAVY PATTERN in the collagen. It allows the fibres to stretch slightly, thereby contributing to the tissue’s ability to cope with mechanical stress.
Under a microscope, non-fatigue-loaded (i.e. normal) tendon exhibits aligned collagen fibrils. What would the collagen fibrils look like in a tendon that has LOW LEVEL fatigue load?
Low level fatigue loaded tendons exhibit kinked fibre deformations.
Under a microscope, low level fatigue loaded tendons exhibit kinked fibre deformations. What would the collagen fibres look like under MODERATE level fatigue load?
Moderate level fatigue loaded tendons exhibit kinked fibre deformations with widening of the spaces between the fibres.
Under a microscope, moderate level fatigue loaded tendons exhibit kinked fibre deformations with widening of the spaces between the fibres. What would the collagen fibres look like under HIGH LEVEL fatigue load?
High level fatigue loaded tendons exhibit severe matrix disruption. The fibres are thinning and there are discontinuities within the matrix.
What shape are tenocytes? And how are they arranged/located within the tissue?
Tenocytes are elongated, and found in chains between collagen fibres. They have long, wide, flat cell processes (the processes aren’t tendril-like).
Tenocyte nuclei can be either ‘blastic’ or ‘cytic’. How could you differentiate between under a microscope?
Blastic = shorter and fatter Cytic = thinner and longer
What is the function of the tenocyte?
In developing tendons, tenocytes produce the collagen and arrange the molecules into fibrils. But their function is less well understood in the mature tendon. It is believed that perhaps the blastic (round/fat) tenocytes produce collagen for repair, and the cytic (long/thin) tenocytes maintain normal tissue function.
Why do tenocytes need to be tolerant to hypoxia (low O2) and hyperthermia (high temp)?
Tendons are very poorly vascularised (low O2 levels). Some tendons are very elastic, which would result in a lot of heat energy being generated within the tissue.
Why do tenocytes have a low metabolic activity rate? And what does this indicate about their general ability to repair/remodel the tendon?
Tendons are very poorly vascularised. Tenocytes have a LIMITED ability to do repair/remodel the fibrils.
What is a bursa and what is its function?
It is a small fluid-filled sac (lined with a synovial membrane) that acts as a lubricated cushion to permit frictionless movement of a tendon over bone. Smooth gliding!
What is a tendon sheath and what is its function?
An elongated bursa that wraps around the tendon to allow frictionless movement of the tendon over bone and under a retinaculum (which is a band of connective tissue). Smooth gliding!
How many polypeptide chains in a molecule of collagen?
Three! Collagen is a triple helix.
Collagen is translated as ___________. How does this become collagen?
Collagen is translated as procollagen. Enzymes cleave the ends off to leave a molecule of collagen.
What guides the formation of the shape of the collagen fibrils?
Collagen is exported from the tenocyte through cytoplasmic furrows, which guides the formation of fibril shape.
Tenocytes are initially round and fat, and bunched together. What happens to them as more collagen is produced?
As collagen is secreted during development and growth, the tenocytes become more distantly spaced. They are joined by long, flat processes.
