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Questions and Answers
What are the three structures that surround and connect the skeletal system?
What are the three structures that surround and connect the skeletal system?
What do tendons connect?
What do tendons connect?
Muscle to bone
Tendons are rich in blood vessels.
Tendons are rich in blood vessels.
False
What is the role of tenocytes?
What is the role of tenocytes?
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The extracellular matrix consists of __% elastin, __% collagen, __% proteoglycan, and __% water.
The extracellular matrix consists of __% elastin, __% collagen, __% proteoglycan, and __% water.
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What does the composition of the extracellular matrix primarily maintain?
What does the composition of the extracellular matrix primarily maintain?
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What allows tendons to straighten during tensile loading?
What allows tendons to straighten during tensile loading?
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Ligaments have collagen fibers that are parallel.
Ligaments have collagen fibers that are parallel.
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What is the outer connective tissue layer of ligaments called?
What is the outer connective tissue layer of ligaments called?
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Tendons and ligaments are described as __ structures, meaning they exhibit both viscous and elastic properties.
Tendons and ligaments are described as __ structures, meaning they exhibit both viscous and elastic properties.
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Which ligament has a greater portion of elastic fibers?
Which ligament has a greater portion of elastic fibers?
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What effect does ageing have on collagen in tendons and ligaments?
What effect does ageing have on collagen in tendons and ligaments?
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Pregnancy decreases laxity in tendons and ligaments.
Pregnancy decreases laxity in tendons and ligaments.
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What is the consequence of immobilisation on tendons and ligaments?
What is the consequence of immobilisation on tendons and ligaments?
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Study Notes
Tendons
- Connect muscle to bone, transmit tensile load, and stabilize joints
- Relatively avascular (minimal blood vessels)
- Composed of tenocytes (~20%) and extracellular matrix (~80%)
- Tenocytes are specialized fibroblasts that control tendon metabolism and respond to mechanical stimuli
- Tenocytes synthesize procollagen which is secreted into the extracellular matrix as collagen
- Extracellular matrix:
- Maintains tendon structure and facilitates its biomechanical response
- Composed of 2% Elastin, 33-50% Collagen, 2% Proteoglycans, and 55-75% Water
- Collagen aligns itself head to tail in a parallel arrangement
- Collagen molecules bind together to form many tendinous layers
- Tendons surrounded by loose areolar connective tissues called paratenon
- Paratenon forms a sheath and helps with gliding
- Crimp:
- Important for biomechanical loading due to the straightening during tensile loading
- Tendon fibers are not straight and parallel
- Elastin:
- Tendons contain a small amount of elastin (~2%) compared to some ligaments
- Ground Substance:
- Solid components mainly contain proteoglycans
- Helps bind water, creating a gel-like substance
- Contributes to lubrication and acts as a cement-like substance
- Helps stabilize collagen and contributes to overall tendon strength
- Tendons load effectively in one direction due to parallel arrangement
Ligaments
- Similar composition to tendons, but have ligamentous fibroblasts instead of tenocytes
- Collagen fibers are not parallel
- Have an outer connective tissue layer called epiligament
- Sustain multidirectional tensile forces
- Collagen fibers in ligaments follow the line of movement and sustain tensile loads in a predominant direction
- The orientation of the fibers within a ligament varies depending on its function
Biomechanical Properties of Tendons and Ligaments
- Both tendons and ligaments viscoelastic structures and strong in tensile loading
- Tendons are strong and flexible enough to angulate around bone surfaces to change the final direction of muscle pull
- Ligaments are strong, pliant, flexible, and inextensible
- Tensile capacity can be represented on a load-elongation curve
- Toe Region: Early elongation with very little load
- Elastic Region: Collagen fibers resist tensile loading, defining the stiffness, ultimate load, yield point, and energy absorbed
- Plastic Region: Very little stretch is possible before failure occurs
- Ligamentum Flavum:
- Has a greater portion of elastic fibers, allowing for 50% elongation before stiffness increases
- Greater elastic region contributes to a larger capacity to elongate before failure
- Viscoelasticity Tests:
- Illustrate the behavior of tendons and ligaments
- Constant Length Test: Tendon stretched to a constant length, the amount of force required to hold that length diminishes over time
- Constant Load Test: Constant load applied to the tendon for a prolonged period of time, deformation increases rapidly at first and progresses more slowly over months
Factors Affecting Biomechanical Properties
-
Maturation and Age:
- Tensile strength and stiffness plateau early in life, then decline with age
-
Pregnancy:
- Increase in laxity of tendons and ligaments in the pubic area due to increased relaxin hormone
-
Mobilisation:
- Similar to bone, tendons and ligaments remodel in response to mechanical demands
-
Immobilisation:
- Decreases collagen production and leads to a decrease in tensile capacity of ligaments and tendons
-
Conditions:
- Comorbidities negatively affect the biomechanical properties of tendons and ligaments
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Description
This quiz covers the structure and function of tendons, including their composition, the role of tenocytes, and the importance of the extracellular matrix. It also explores how tendons stabilize joints and their biomechanical properties, including crimp and gliding mechanisms. Test your knowledge on this essential connective tissue!
