Kines Week 3
The structures are the same in all tissues, but the ____ of the structures change.
%
What does "strain" refer to?
% of deformation
What are the functions of tendons?
-Attach muscle to bone -Transmits the forces of the muscle and gives advantage to the muscle -Transmits tensile loads with minimal energy loss -Advantage mechanical pulley
What are the 2 types of bone?
-Cancellous bone (trabecular, sponge) -Cortical bone (compact)
What are the fibrillar components?
-Collagen -Elastin
What are the functions of ligaments?
-Connect bone to bone -Stability to the joint -Guides, checks, limits, joint motion -Prevent excessive motion
When the rate (frequency) at which a load is applied is high, this could cause strain injuries, also known as _____. What are examples of this?
-Cumulative Trauma Disorders (CTD) -Examples: Tendonitis, carpal tunnel syndrome
What are 5 factors that can decrease a person's bone mineral density, or bone stiffness?
-Disuse -Inactivity -Weightlessness -Older age -Poor nutrition
Explain the composition of the ECM of cartilage
-Fibrillar: Type II collagen -Interfibrillar: Composed of hydrated networks of proteins, GAGs and PGs (aggrecan)
What are the 3 different types of cartilage called?
-Fibrocartilage (disc/menisci/TMJ) -Elastic cartilage (external ear/ epiglottis) -Hyaline cartilage (synovial joint)
Does the organic or inorganic components of bones give their flexibility and resiliency? Does the organic or inorganic components of bones give their hardness and rigidity?
-Flexibility & resiliency: organic components -Hardness & rigidity: inorganic components
What are all of the parts of the PG aggrecan?
-Hyaluronic acid chain (where the PG attaches to) -Link proteins (how the PG attaches to the HA) -Protein core (where the GAGs attach to) -GAGs (Keratin sulfate and Chondroitin sulfate)
The extracellular matrix (ground substance) is made up of which 2 components?
-Interfibrillar matrix -Fibrillar
Explain why cartilage is a porous, permeable, fiber-reinforced composite matrix
-It is porous because it allows exudation. -It is permeable because water can come in and out of it. -It is fiber-reinforced because collagen type II fibers maintain its structure.
Connective tissues are most of the structures in the body. What are the 3 different classes of connective tissues?
-Loose -Dense -Specialized CT
How do tendons have vascularization? Meaning, where do they receive their blood supply from?
-Muscle (perimysium) -Bone (periostal insertion) -The surrounding tissue (vessels via paratenon or mesotenon)
What are the cells that make up bone?
-Osteoblasts & osteocytes (bone forming cells) -Osteoclasts (remodeling cells)
What are the intrafibrillar matrix components?
-Water -Proteoglycans (PGs) -Glycoproteins (GAGs)
What is the function of a bursae?
-Reduce friction and facilitate movement -Similar structure to tendon sheaths
If you compare a stress/strain curve of a healthy bone to an osteoporotic bone, what differences may you notice between the two?
-The amount of strain/deformation is slightly similar. -The amount of stress/load is much lower in the osteoporotic bone than the healthy bone.
What are the 2 ways to analyze viscoelastic behaviors?
-The creep deformation -The stress-relaxation
When looking at the stress/strain curve: The more area, the ____ (more/less) stress. The more load, the ____ (more/less) stress.
-The more area, the LESS stress. -The more load, the MORE stress.
What 3 things does the quantity of PGs/GAGs affect?
-Tissue hydration -Tissue's tensile and compressive strength -Rigidity of the tissue
The types of stress and strain depends on what 4 factors?
-Type of load -Direction/ position of load -Magnitude of load -Material/characteristics of structure
Describe the swelling-pressure changes in the ECM (step by step)
1) A load is applied → 2) Internal pressure increases → 3) Some water is pushed out → 4) PGs then get really close and their negative charges repulse each other which produces rigidity → 5) The trapped collagen is maintaining the structure of the area → 6) Once the load is gone, water comes back in via attraction of PGs with water solutes NA and CA→ 7) Equilibrium reached/ return to normal shape
Lubrication of a joint depends on these 3 things. Describe each: 1) Boundary lubrication 2) Thin fluid-film lubrication 3) Mixed lubrication
1)Boundary lubrication: each surface is protected by a monolayer of lubricant which prevents direct surface-to-surface contact. 2) Thin fluid-film lubrication: provides greater separation of joint surfaces. 3)Mixed lubrication: has both of the above
Collagen formation and degradation are two steps in the tissue remodeling & repairing processes. Net synthesis of collagen is found around how many hours after exercise?
36-72 hours
Cancellous bone can sustain strains of ___% (but at lower stresses) before failing.
75%
Since cortical bone is very mineralized, this means it can: a) Absorb a lot of stress & deform very little b) Deform a lot & absorb less stress c) Absorb a lot of stress & deform a lot d) Deform very little & absorb less stress
A
What is Tropocollagen?
A building block that is a triple-helix collagen molecule.
Briefly describe what a bursae is
A fluid-filled sac covered by a synovial membrane.
Describe the peritenon
A synovium-lined sheath called the tenosynovium.
Describe what the endotenon is
A thin film of loose CT between tendon fascicles that facilitate the sliding movement and create a conduit for blood vessels. The endotenon binds groups of fibers into fascicles of motor units. Enclosed nerves, blood and lymph vessels.
Describe viscoelasticity
A type of biphasic behavior that is also time and rate dependent. This means that the deformation behavior depends on: -The amount of load -How long the load is applied for (time) -How frequent the load is applied (rate)
Adequate loading of connective tissues enables the adaptation to do what? What about inadequate loading?
Adequate loading: strengthen the collagenous tissue. Inadequate loading: may lead to injuries.
Since cartilage is resistant to compressive forces, it thus depends on a large volume of ____ and ____.
Aggregating PGs & an intact collagen network
Heterogenous materials exhibit ____ behavior. What does this mean?
Anisotropic behavior. This means that different types of loads and different positions of loads will determine the mechanical behavior/response.
Where on a bone are cancellous bone located?
At the epiphysis (the ends of bones) which are the loading surfaces
Which is the most prevalent type of structure in the ECM of a ligament? a) Majority elastin, low PGs, low type I collagen b) Majority type I collagen, low PGs, low elastin c) Majority PGs, low type I collagen, low elastin
B
Why is joint movement important in cartilage health?
Because cartilage needs nourishment.
Why are cortical bones more stiff then cancellous bones?
Because cortical bones have more mineralization, which causes more stiffness.
Why is cartilage considered a biphasic structure?
Because it has a structural AND fluid component.
Why are bones considered specialized?
Because it is mineralized
In both tendons and ligaments, the collagen fibers are arranged parallel and in the direction of the applied load. Why are the fibers in tendons MORE parallel than in ligaments?
Because ligaments can have some multidirectional movements.
Why do cartilages contain a lot of "gel" or fluid
Because they contain the proteins that attract water.
What are some GENERAL examples of connective tissues?
Bones , tendons, bursae , capsules, cartilage, discs, fat pads, labrum, menisci.
Does bone exhibit both elastic and plastic properties? Or only one of those?
Both plastic and elastic
Bone absorbs both compression and tensile loads. However, more ____ than ____.
Both. But more compression than tensile.
____ material tends to fail before permanent deformation. ____ material deforms greatly before failure.
Brittle Ductile
Which type of connective tissue is hydrodynamic in nature? a) Tendon b) Ligament c) Cartilage d) Bone
C
Which type of bone contains many "tunnels" and "cavities"? Cancellous or Cortical?
Cancellous
____ bone reduces load/impact, is found around joints, and has a higher % of deformation.
Cancellous
Which has more PGs in their ECM? a) Cartilage b) Ligament c) Tendon
Cartilage
What are 2 examples of specialized connective tissues?
Cartilage and bone
Which term describes: biomechanical signals induce biological (and pathological) processes.
Cellular mechano-sensitivity
What is the cellular component for cartilage?
Chondroblast & chondrocyte
What structure does this describe: The functional integrity of connective tissue structures and resistance of connective tissue to tensile forces.
Collagen
Describe Sharpey's Fibers in ligaments and tendons
Collagen bundles from the roots of the tendon/ligament that extend from the into the bone.
Describe how collagen uses cellular mechano-sensitivity to maintain tissue homeostasis.
Collagen molecules sense mechanical forces, then produce signals through deformation at the molecule level, to enable tissue remodeling and repairing.
What type of collagen is found in the ECM of fibrocartilage?
Collagen type I and type II
What are the organic components in the ECM of bone?
Collagen type I, water, PGs
Collagen degradation is regulated by what to clean up the "mess" during remodeling?
Collagenases
Which type of load do bones transmit?
Complex loading (tension & compression?)
Which type of load does cartilage mostly absorb in the body?
Compression loads
Cartilage formation and health is dependent on alternating cycles of moderate ____ (which type) forces.
Compressive
____ bone is stronger and stiffer and gives the skeleton its strength to withstand load.
Cortical
The arrangement of collagen fibers allows for some deformation. What is the wavy configuration of collagen fibers called when in its relaxed state?
Crimp
What is the inorganic component in the ECM of bone?
Crystals of hydroxyapatite (Calcium, Phosphate)
Cancellous bones are not as stiff, which means they can ____.
Deform a lot.
What term does this describe: The length change, or deformation, is directly proportional to the applied loads or forces. As load is applied, there is deformation and energy increases. When the forces/load are removed, the object will return to its initial shape and size. This material stores this energy for immediate recoil back to original shape.
Elasticity
A type of cartilage called elastic cartilage, has a higher ratio of ____ fibers and is found in the ears and the epiglottis.
Elastin
At the myotendinous junction, the meshwork of connective tissue around the muscle fibers involves the endotenon blending into the ____, and the epitenon blending into the.
Endomysium, epimysium
Tendon fascicles slide independently against each other, and the ____ protects them.
Endotenon
The point of insertion of a ligament to a bone is called the ____, and is the high stress concentration point.
Enthesis (Osteo-ligamentous insertion)
True or False: Cartilage is only responsible for providing low-friction movements, and does not have the capability of weight bearing and distribution of loads.
False- cartilage does all of that.
True or False: You sacrifice mobility for stability in a joint, because you cannot have both.
False- joints have both mobility and stability. A joint needs stability to generate mobility.
True or False: Static structures can contract on their own. What is an example of a static structure?
False- static structures cannot contract on their own. Example: tendons and ligaments
True or False: The failure of a ligament happens in the enthesis.
False- the failure of a ligament happens in the body of the ligament.
True or False: A structure with a greater cross sectional area can withstand less force but with more deformation than a structure of the same length with less cross sectional area.
False. A structure with a greater cross sectional area can withstand MORE force with LESS deformation than a structure of the same length with less cross sectional area.
True or False: Cancellous bones are more stiff and less deformable than cortical bones.
False. Cancellous bones are more deformable and less stiff compared to cortical bones.
True or False: Fibrocartilage is avascular.
False. It has some blood supply (limited to peripheral regions) so it is hypovascular.
True or False: When loads are reduced over time, this will strengthen the myotendinous junction and thus strengthen the tendon overall.
False: a decrease in load over time will make the tendon weaker.
True or False: Cancellous bone can withstand greater magnitudes of stress with less deformation (strain) than cortical bone.
False: opposite. Cortical bone can withstand greater magnitudes of stress with less deformation (strain) then cancellous bone.
True or False: Remodeling only occurs when there is injury in the body.
False: remodeling is always occurring.
True or False: You can only load a cartilage with weight-bearing.
False: you can both load a cartilage every time the joint surfaces are moving or with weight-bearing.
Does bone fail fast or slow after passing the yield point on the load/deformation curve?
Fast
How are the collagen fibers arranged in ligaments to best resist tensile forces?
Fibers are arranged parallel (but not as parallel as seen in tendons) and in the direction of all imposed tensile forces.
What is the precursor cell for collagen?
Fibroblast
What is the cellular component for collagen?
Fibroblast & fibrocyte
What specific structure within connective tissues are mechano-sensitive?
Fibroblasts
Describe the formation sequence from tropocollagen to fibers/ fascicles.
Fibroblasts synthesize tropocollagen → tropocollagen aggregates to form microfibrils → microfibrils come together to form fibrils → fibrils come together to form fibers → fibers come together to form fascicles/ bundles.
In SHORT bones, what is the point of insertion called for a ligament onto a bone?
Fibrocartilaginous enthesis
What do the immature/precursor connective tissue cells mature into?
Fibrocytes, chondrocytes, osteocytes, tenocytes,
What do PGs contain that are the brush-like structures that attract water?
GAGs
What does a hydrodynamic structure mean?
Has the in and out movement of water
Which types of tissues have the "toe region" in the stress/strain curve? Which ones do not?
Have toe region: Tendons and ligaments Do not have toe region: Bones and cartilage
The compactness of the cortical bone is called the ____.
Haversian system.
Are ligaments composed of heterogeneous or homogeneous structures?
Heterogeneous structures
A viscoelastic material loaded at a FASTER rate will have a ____ (higher/lower) peak stress than a material loaded at a LOWER rate.
Higher
Are bones highly vascular or avascular?
Highly vascular
In what type of connective tissue is the PG aggrecan located in?
Hyaline cartilage
How do you compare, or how can you discriminate, between hyaline cartilage and fibrocartilage based on their cells?
Hyaline cartilage: chondroblast > chondrocyte Fibrocartilage: fibroblast > fibrocyte AND chondroblast > chondrocyte
The composition of the materials of a joint tells you the biomechanics of the joint. If you see a joint that has a lot of cartilage, what can you assume about the biomechanics of it?
If a joint has more cartilage, you can assume that joint holds/carries a lot of weight.
The composition of the materials of a joint tells you the biomechanics of the joint. If you see a joint that has a lot of ligaments/tendons, what can you assume about the biomechanics of it?
If a joint has more ligaments/tendons, you can assume that joint needs stability.
When might collagen degradation exceed collagen synthesis?
If there are no mechanical loads being applied to the body.
Where specifically is collagen located?
In the ECM, specifically in the fibrillar component.
In general, where are bursae usually located?
In tight areas
What are fibrils strengthened and stabilized by?
Inter and intramolecular cross links
Describe the paratenon
Involves healing and cell replacement
Homogenous materials exhibit ____ behavior. What does this mean?
Isotropic behavior. This means it exhibits the same behavior/response regardless of where the force is applied on the structure.
Describe Utah's Law
It builds on Wolff's Law in saying that mechanical properties effect the growing a remodeling of bone. but NON-mechanical properties do as well.
What is Aggrecan? What does it attach to in cartilage?
It is a cartilage-specific PG, and attaches to hyaluronic acid chains in cartilage.
Describe the load deformation curve
It plots the magnitude of the applied load to the amount of deformation. It gives information about a material's strength, stiffness, and stored energy.
Describe the epitenon
It surrounds the tendon as a whole and has synovial fluid to facilitate sliding.
Joint function depends on ____.
Joint composition (structure and composition)
In cartilage, which types of GAGs are in the aggrecan? What do those GAGs attract to them? How?
Keratin sulfate and Chondroitin sulfate. They attract water because the water has a positive charge while the GAGs have a negative charge.
In the bone/ligament junction, list the 4 zones in order from least stiff to most stiff.
Least stiff: Zone 1 Zone 2 Zone 3 Most stiff: Zone 4
Fibrocartilage ECM has type I and II collagen, as well as water and PGs. Does fibrocartilage have more or less PGs than hyaline cartilage?
Less
When a tensile load is applied, ____ limit the amount of translatory motion in the joint.
Ligaments
How do PGs attach to hyaluronic acid?
Link proteins
Does cartilage have high or low vascularity?
Low
Does cartilage have a low or high ability to heal and repair? Why?
Low. Because of its low vascularity.
What is an example in the body of a ligament having some vascularity?
MCL
Which is more vascular: MCL or ACL?
MCL
In cartilage, the rate of fluid flow is affected by the ____ and ____ of the applied force.
Magnitude & duration
In both Wolff's Law and Utah's Law, each agreed on the most important factor to maintain bone health homeostasis is what?
Mechanical loading
ECM turnover is influenced by what?
Mechanical loading/ physical activity
What mediates the collagen degradation rate, which then likely initiates the remodeling processes in connective tissues?
Mechanical loading/forces
What are examples of mechanical and non-mechanical properties that effect bone growth and remodeling? (+/-)
Mechanical: The presence or absence of muscle contraction, body weight, gravity, range of motion in joints. Non-mechanical: Diet/nutrition, sun exposure/ temperature, hormones, age, gender
What are examples of where fibrocartilage is found in the body?
Menisci, intervertebral discs
Tropocollagen aggregates to form what?
Microfibrils
In ligaments, are there more cells or ECM? What are the distributions of each?
More ECM than cells: 10-20% cells (fibroblasts) and 80% ECM.
Does hyaline cartilage have more amounts of ECM or more amounts of cells?
More ECM, little amount of cells.
If a structure contains more collagen than PGs, which type of forces do they typically absorb? If a structure contains more PGs than collagen, which type of forces do they typically absorb?
More collagen= Tensile loads More PGs= Compression loads
Can bone withstand greater stress (with less strain) more in tension or more in compression?
More compression than tension.
What is the most basic (immature/ precursor) cell of most connective tissues? What are the most basic (immature/ precursor) cells for special connective tissues?
Most connective tissues: Fibroblast Specialized connective tissues: Chondroblast, Tenoblast, Osteoblast
What does the SAID principle stand for? Explain.
Specific Adaptation to Imposed Demand This says that each tissue will respond differently to a demand.
If there is inflammation in a tendon or ligament, where in the tendon/ligament is it most likely to see the inflammation? Why?
Most likely at the enthesis (point of insertion). Because this is where most of the stress/load is in the tendon/ligament.
What is the most abundant type of collagen found in cartilage? What other component is there a lot of?
Mostly Type II collagen and lots of PGs (more PGs than collagen).
At the Myotendinous junction, there is a strong interdigital connection between ____ and ____.
Muscle cells and collagen
What is the best stimulus of collagen for tendons?
Muscle contraction
What is the insertion point called at the tendon and muscle?
Myotendinous junction
How are different bursae named in the body?
Named based on area it is found (sub cutaneous, sub tendinous, sub muscular).
For hyaline cartilage, do the chondrocytes have homogeneous or nonhomogeneous distribution?
Nonhomogeneous
Ligaments ONLY transmit which type of load?
ONLY tensile forces
Where are on the bone is cortical bone located?
On the shaft (diaphysis) of the bone AND on the ends (epiphyses) of the bone- covering the cancellous bone too.
In cartilage, the delivery of nutrients is dependent on what type of pressure?
Osmotic pressure
What is the cellular component for bone?
Osteoblast, osteocyte, osteoclast
In bone, when there is more remodeling than than formation, what occurs?
Osteoporosis (when osteoclast activity exceeds osteoblast activity).
Tissues that resist high compressive forces have a high % of ____.
PGs/ GAGs
What is the best stimulus of collagen for ligaments?
Range of motion of a joint
The insertion point for ligaments is the fibrous enthesis, which is cemented into mostly cortical bone via ____.
Sharpey's Fibers.
Describe the plastic region on the stress/strain curve
Shows how much load a tissue can withstand without breaking (which would be at the point of fracture). However, unlike in the elastic region, once the tissue has sustained an amount of load in the plastic region, it risks being deformed to some extent and may not be able to go back to it's original state once the load has been released.
The greater the slope (steeper) of the elastic region, the more ____. The less slope (gradual) of the elastic region, the more ____.
Stiffer More deformable
How does elastin deform when a load is applied?
Straighten out when stretched; shrink when unloaded. Elastin deforms under an applied load then returns to original shape.
Cartilage nourishment depends solely on what?
Synovial fluid flow (which is a result of pressure changes from loading/unloading).
Which connective tissue structure connects muscle to bone and transmits muscle forces to bones?
Tendons
Which one typically has more type 1 collagen fibers: tendons or ligaments?
Tendons
Right now we will be focusing on dense connective tissues and specialized connective tissues. What are 2 examples of regular dense connective tissues?
Tendons and ligaments
What is the cellular component for tendon?
Tenoblast & tenoctye
After exercise, the connective tissues are remodeling. What does this imply?
That there's direct coupling between synthesis AND degradation of collagen. This means it is a repairing process to maintain homeostasis.
What is an example tendon in the body that has vascularity?
The Achilles tendon
What plays a key role in force transmission and tissue structure maintenance?
The ECM
What does "stress" refer to?
The amount of load per unit area.
Describe Wolff's Law
The application of forces stimulate osteoblasts and as a result, bone mass increases. With reduction of usual forces, osteoclast activity predominates and bone mass decreases.
Describe the elastic region on a stress/strain curve
The area where a material can return to its original shape after a load is applied and then removed. The slope of the load in this area is linear. Steer slope= stiffer Gradual slope= more deformable
If a scar on your body is healing and you notice it start to bubble, what happened?
The body produced too much collagen- keloid formation.
What needs to occur in order for the extracellular structures to be produced?
The intercellular immature cells are metabolically active and need to mature to produce the extracellular structures.
Cortical bone is covered by periosteum. What is the purpose/function of the periosteum?
The periosteum is filled with osteoblasts that will help with growth and repair of the cortical bone. It also acts as a tissue sheath.
What is another word for the elastic range on the stress/strain curve?
The physiologic range
Ligaments are hypo vascular, or even more so- avascular. Any vascularization of a ligament, will be located at which part of the ligament?
The point of insertion onto the bone (the bone/ligament junction).
What is endochondral ossification?
The process by which growing cartilage is replaced by bone to form the growing skeleton during fetal development.
Describe how homeostasis is maintained in connective tissues when it senses motion or loads.
The production or degradation of collagen is regulated according to the incoming signals to maintain homeostasis.
In ligaments, what accounts for the relative abilities to provide stability and allow for mobility at a specific joint?
The ratio of collagen/ elastin
What structure is responsible for the tendons being able to change shape as their muscles contract, and to transmit tension despite the changing angles of a joint?
The tendon fascicles being covered by the endotenon.
Describe what hyaline cartilage is
The thin cartilage covering the ends of bones within a joint.
When a load is applied RAPIDLY to a viscoelastic material, what initially happens to the material? What does this reaction display?
The tissue will get very stiff, and a larger force is needed to deform the tissue than if the load was applied SLOWLY. When a tissue is loaded rapidly, a large peak force is required to deform the tissue. This reaction displays the strain-rate sensitivity of viscoelastic materials.
Describe the yielding point on the stress/strain curve
The transition between the elastic and plastic regions. This yielding point can be passed either because of too much load or too much deformation. When the yielding point is passed, it enters into the plastic region.
What does "biphasic" behavior mean?
There is a fluid phase or a solid phase
What is the formation of elastin fibers like?
They are cross-linked to each other and in straight lines.
When a load is applied to a connective tissue, what happens to the configuration of collagen fibers?
They get stretched out. When the load is removed, they return back to the crimp formation (relaxed state).
What is the small area between the calcified and uncalcified cartilage called?
Tidemark
Cancellous bones form ____ in response to stresses placed upon it.
Trabeculae
Describe fibrocartilage. Where is it found in the body?
Transitional cartilage. Found in joints with little motion. See in IV disks, labrum, and SIJ & TMJ.
When compared to collagen, elastin has single alpha-like strands without a ____?
Triple helix
To form microfibers, fibroblasts need to synthesize what?
Tropocollagen
True of False: Bone adapts its mechanical properties according to the needed mechanical function.
True
True or False: A longer structure deforms more when a force is applied than does a shorter structure of similar cross sectional area.
True
True or False: An injury can be because of stress OR strain (load OR deformation).
True
True or False: Cartilage is hypo-cellular and avascular.
True
True or False: Hyaline cartilage is NOT located on the entire length of a bone- only on the ends of bones (such as within a joint).
True
True or False: Ligaments are often capsular but can be distinct as bands or cords.
True
True or False: PGs and GAGs also act as reservoirs for nutrients & growth factors.
True
True or False: Tissues always adapt to functional demands.
True
Ligaments have mostly which type of collagen?
Type I
Which type of collagen is a major load bearing element and has high strength & deformation under tension?
Type I
Which type of collagen is found in almost all CT (90%); predominantly in bone, ligaments, tendons, menisci, synovium, etc.
Type I
Which type of collagen is the most important for tensile forces?
Type I
What type of collagen fiber is in the ECM of bone?
Type I collagen
Which type of collagen bears tensile and compressive forces, and is found in articular cartilage and in the nucleus of intervertebral disks?
Type II
Which type of collagen has a large affinity with PDs (especially in cartilage and discs)?
Type II
Which type of collagen has sheaths within muscles, facilitates new scar tissue/healing, and is found in the skin and fibrous joint capsules?
Type III
Wolff's Law is centered around mechanical properties only, while Utah's Law is centered around mechanical properties and what else?
Utah's Law: mechanical + non-mechanical properties.
Tendons that have a paratenon are referred to as ____ tendon.
Vascular
When analyzing viscoelastic materials, describe what the Histeresis Loop is
Viscoelastic materials exhibit a time delay (lag) in returning the material to original shape after a load is removed, and some energy is lost during this process (released as heat). This "lag" displayed on the graph is the Histeresis Loop and shows how much energy was lost while retuning to original shape after load is removed. The area underneath the loop represents the energy that was returned after the load was removed.
Describe the "creep" phenomenon when analyzing viscoelastic materials. Examples?
When a constant load is held over a period of time, the tissue rapidly deforms INITIALLY, until equilibrium is reached. When the load is eventually removed, it may not return to its original shape, and if it does, it may take a long time. There may be continued deformation of a viscoelastic material after the load has reached a constant state. Examples: braces or scoliosis (continued deformation)
When analyzing viscoelastic materials, describe the stress-relaxation concept.
When a material is deformed to a fixed length, the force required to MAINTAIN the new length deformation decreases over time. Essentially, less force is required to maintain the same tissue length and there is continued reduction in stress inside the viscoelastic material.
The water-binding characteristic of the GAGs in aggrecan is what gives cartilage the ability to do what?
Withstand compression
Describe the 3 zones of cartilage structure
Zone 1) Tangential zone: The outermost zone where collagen fibers are very parallel. ↓ Zone 2) Transitional zone: The middle zone where there is a meshwork of collagen and PGs to become transitional. ↓ Zone 3) Radial zone: the end of the cartilage that becomes rooted, or anchored, into the bone and becomes mineralized/ calcified. ↓ Subchondral bone ↓ Cancellous bone
Describe the 4 zones of a bone and ligament/tendon insertion or junction.
Zone 1) Tendon or Ligament Zone 2) Unmineralized fibrocartilage Zone 3) Mineralized fibrocartilage (Sharpey's Fibers) Zone 4) Bone
What is Hyaluronan?
a GAG that does not attach to a protein core but could have large numbers of PGs attached to it (i.e. in cartilage).
Which type of slope below is seen in bones? Cartilages? Tendons/Ligaments? Slope a) | Slope b) / Slope c) -
a) bones (mostly vertical slope) b) cartilages (mostly diagonal slope) c) tendons/ligaments (mostly horizontal slope)
Tendons are similar in composition to ligaments in that they each contain type ____ collagen fibers.
type 1 collagen
