Kinesiology Module 2 - Joint Structure and Function

Give Two Examples of Loose CT

-Adipose -Reticular

What 3 things does lubrication of the cartilage depend on?

-Boundary lubrication -Thin fluid fill lubrication -Mixed lubrication.

Where is cortical bone and cancellous bone found in a long bone?

-Cancellous bone is found at the epiphysis on each end, where there is the most load. -Cortical bone surrounds the entire long bone (epiphysis and the diaphysis)

Give Two Examples of Specialized CT

-Cartilage -Bones

Describe hyaline cartilage

-Cellular component: fibroblast, chondrocytes. -Extracellular components: collagen type II (fibrillar) and a hydrated network of proteins such as proteoglycans and glycoproteins, most commonly aggrecan. -Avascular and hydrodynamic in nature, meaning it does not receive nourishment from blood vessels, rather it gets its nourishment through alternating cycles of compressive forces that allow for fluid flow in and out.

What makes bone unique compared to the other kinds of connective tissue?

-Cellular level: osteoblasts. -Fibrillar components: mostly collagen type I fibers, elastin and reticular fibers -What makes bone unique is that the ECM matrix contains lots of minerals like calcium and phosphate and hydroxyapatite. Furthermore, bones also contain osteoclasts, which unlike osteoblasts which build bone, they remodel bone.

How are collagen and elastic different?

-Collagen are in a triple helix molecule -Elastin is in a single-alpha strand. -Collagen is in a crimp state when relaxed and can stretch out to resist tensile forces -Elastin are cross linked so when they are stretched to resist tension, they snap back into place into their original formation.

What is the difference in bone strength and stiffness in cortical vs cancellous/trabecular bone?

-Cortical bone is stronger and stiffer than cancellous/trabecular. It gives the skeleton strength to withstand load. -Cancellous/Trabecular bone reduces load/impact and is found around joints. They have a higher percentage of deformation and therefore a decreased level of stiffness than cortical bones

What factors influence joints?

-Genetics -Cellular Activities -Tissues Adapting to Functional Changes -Changes in the shape of tissues occur as we grow and if an injury occurs

What are three factors that affect tissue response?

-Individual Capabilities -Environment -Demands

Main components of Cancellous/Trabecular Bone?

-It is found in load-bearing surfaces of bones -Undergoes self-remodeling -Covered by a layer of dense cortical bone -Reduces load/impact -Higher percentage of deformation

Give 3 examples of how tissue structure is affected

-Nourishment -Disease States -Aging

How would you want to increase the strength of a tissue/muscle?

-Progressive Overload You must change its ability to generate forces by applying loads of certain magnitudes. Overtime, the muscle will get accustomed to said load and it will more easily produce the necessary force to overcome it. As a result, to continue its progress of strengthening, you must consistently add greater loads to continue challenging it without injuring it

What is the difference between stress and strain?

-Stress is the amount of load placed on a unit of area -Strain is the amount of deformation that occurs when a load is placed on a bone

Give Two Examples of Dense CT

-Tendons -Ligaments

How does bone density in the legs change in someone who walks all day (active lifestyle) compared to someone who is immobilized because of a leg injury?

-The bone density in the legs will be much higher in someone who is constantly walking around and being active. This is because they are constantly applying force and force is the main driver in remodeling and building bone. -Someone with a leg injury who is immobilized for the time being will have decreased bone density, especially in the injured leg. They will not be applying any force (not using it) and that will not increase the building process but more so just increase degradation.

What are some main characteristics of Cortical (Compact) Bone?

-The cortical bone is the thin, outer-covering; it is covered by the periosteum -It has a reservoir for cells such as osteoblasts for growth and repair -It is well vascularized -Highly organized by the Haversian System -Strong and Stiff because it is mineralized -Can withstand great load

What components make the bones hard and rigid and where are they found?

-The inorganic components of the extracellular matrix allow the bone to be hard and rigid. -The inorganic components are crystals of hydroxyapatite which is a calcium-containing mineral that allows for the bone to have strength and stiffness.

What type of fibers are found in bones and what properties do they allow bones to have?

-Type I collagen, Elastin, Reticular fibers Give bones flexibility and tensile strength

What are the 5 things that stress and strain in human tissue depend on?

1. Material 2. Type of load applied 3. Point at which the load is applied 4. Direction and magnitude of the load 5. Rate and duration loading

Which of the following is TRUE about cortical and cancellous bone? a. Cortical bone can withstand greater magnitudes of stress with less deformation (strain) than cancellous bone b. Cancellous bone can withstand greater magnitudes of stress with less deformation (strain) than cortical bone c. Cortical bone can withstand less magnitude of stress with less deformation (strain) than cancellous bone.

A

Explain the differences in the graphical appearances of a ligament/tendon and a bone load-deformation curve.

A ligament/tendon load-deformation curve will feature a "toe" region which is representative of the ligament or tendon fully stretching prior to any deformation. A bone deformation will typically have a much flatter plateau past the yield point where a ligament or tendon curve will continue to rise more in the plastic region.

What effect does cross-sectional area have on the force absorbed and degree of deformation?

A tissue with a greater cross-sectional area can withstand more force with less deformation than a tissue of same length with a lesser cross-sectional area.

What is the most important factor in maintaining bone health?

According to Wolff's law and Utah's paradigm the most important factor in maintaining bone health is applying a mechanical load to the bone as this stimulates the osteoblast activity.

When something like ligaments or cartilage are described as avascular what does this mean?

Avascular means that these components do not have a blood supply coming to them so when a ligament or cartilage are avascular they will not be able to heal on their own from a lack of blood.

Using the concept of the load/deformation curve, explain why bone is brittle?

Bone exhibits both elastic and plastic properties. However, when looking at the load/deformation curve for bone, you will see that it fails "fast" after the yield point. Thus, it tends to break before permanent deformation, which makes it brittle.

What property makes bone a specialized connective tissue?

Bone is a specialized connective tissue because it is mineralized. Bone has an inorganic component, which is comprised of calcium, phosphate and crystals of hydroxyapatite. It is hydroxyapatite that gives bone its properties of rigidity and hardness.

How do you keep your bones healthy?

Bone is dynamic, which means it can adapt to mechanical and non-mechanical stimuli and change its shape and composition. In order to keep bone healthy, it must be constantly receiving external stimuli, through biological mechanisms and most importantly mechanical loads. This causes the osteoblasts in bone to form more bone, which leads to increase in mineral density and allows bone to become stronger. If one were to be immobile or sedentary, osteoblasts would not function as much and osteoclasts would predominate, causing bone to decrease in density and strength, and thus overall health.

How are collagen and elastic similar?

Both function to be able to resist tensile forces in the body.

What are bursae and what is their function?

Bursae are flat sacs of synovial fluid that are found in tight areas and their role is to reduce friction and facilitate movement

Which of the following terms is described in the description below? "when the forces/load are removed, the object will return to its initial shape and size" a. Viscosity b. Loss of energy c. Elasticity d. Stress

C - Elasticity

When people age, why does their osteoclast activity dominate over their osteoblast activity? A. Age naturally increases osteoclast activity B. Individuals in older populations usually live their life with less bone stimuli C. Both a and b D. Osteoblasts are not found in older populations

C - both a and b are true because it has been found that when older people exercise more and stay more active, bone health can increase

Which tissue type exhibits a "toe" region on its stress-strain curve graph? A. Bone B. Cartilage C. Tendon/ligament D. Epithelial

C - the correct answer is tendon/ligament because the "toe" region signifies the time before the structure of the tendon/ligaments were stretched out to their actual length (because they begin in a wavy-like pattern) and started to experience tension leading to the yielding point.

What is a cellular factor of fibrocartilage? A. Osteoblasts B. Chondrocytes C. Fibroblasts D. Osteocytes

C. Fibroblasts

What are examples of minerals found in bones and what compound do they create?

Calcium and phosphate are found in bone and create hydroxyapatite

What kind of bone would you expect to find in the calcaneus?

Cancellous Bone because it helps with distributing load (decreasing stress)

What is the difference between cancellous and compact bone?

Cancellous bone contains trabeculae or tunnels and is usually only found at loading surfaces so that they may distribute the loading forces. Compact bone is a solid layer of bone around the entire bone and has periosteum on the outside

Explain the difference in location between the cancellous (trabecular) bones and the cortical bones

Cancellous bones are found inside the weight bearing region of bones. They undergo self-remodeling and reduce load/impact. Cortical bones, on the other hand, are found on the outer covering of bones, covering the cancellous bone. They are well vascularized and composed of osteoblasts for growth and repair.

Describe fibrocartilage

Cellular component: fibroblasts, fibrocytes, and fibrochondrocytes. -It is less hydrated and contains less PGs than hyaline cartilage does. Extracellular Component: collagen types I and II (mostly I) -Hypovascular. Because it has some vascularity, it is able to receive nourishment from the circulatory system to some degree, thus it is somewhat regenerative.

What are the components of fibrillar ECM

Collagen and Elastin

The form of human tissues is determined by the overall _______ and ________ of connective tissues and by functional use

Composition and Structure

What kind of forces does type II collagen resist?

Compressive and Tensile forces Due to high affinity to PGs

We observed 2 types of bones: cancellous bones and cortical bones. Which of these two types of bones are located on BOTH the diaphysis (shaft of bone) AND the epiphysis (ends of bones)?

Cortical bone

Does cancellous or cortical bone have a higher density?

Cortical bone has a higher density, because the higher the density the higher the stress. In addition to high stress, it has increased mineralization, but cannot deform very much.

When referring to viscoelasticity, what is Creep?

Creep is the phenomenon that happens a force or load is applied onto a tissue over a long period of time, after which the tissue becomes somewhat deformed when compared to its original state. After it has been held there for a long amount of time and the load is finally released, the tissue will try to reform into it's original state, however, it will be unable to completely go back to how it originally was before.

Describe viscoelastic creep

Creep is the process of a tissue returning to its original shape after being acted on by load. As load acts on a tissue over a period of time, the respective tissue deforms rapidly until equilibrium is achieved. When the load is removed, it will take time for the tissue to return to its original shape (shape when not under load).

What factors contribute to a decrease in bone health?

Disuse, inactivity, weightlessness, age, poor nutrition

What type of tissue is the most vascularized? A. Cartilage B. Adipose C. Tendons D. Ligaments E. Bone

E - bone is the most vascularized out of those options

What steps does a cell take to get to a mature bone cell?

Fibroblast > Osteoblast > Osteocyte

If mechanical stress is equal to the internal forces created by an applied load, then what happens to the stress when the force is greater than the applied load? What happens when the force is less than the applied load?

Greater applied force would mean greater mechanical stress, and if the load is greater than the force applied, it would signify decreased stress. If F > A then there's increased stress If F < A then there's decreased stress. (where F = force and A= load per unit of area)

Bones are specailized becasue they have the ability to mineralize. What is the mineral component that makes bones mineralized?

Hydroxyapetite (which is calcium + phosphate)

What is the difference between the Elastic and Plastic Region when it comes to a Load-Deformation curve?

In a Load-Deformation curve (or a Stress-Strain curve), The Elastic Region shows how much Load (or stress, depending on the chart) a tissue is able to withstand and will be able to go back to it's original state, without injury, after the load has been released. The Plastic Region, on the other hand, shows how much Load (or stress, depending on the chart), 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 will be deformed to some extent and will not be able to go back to it's original state once the load has been released

What is the difference between anisotropic and isotropic behaviors?

In isotropic a structure's mechanical behavior will be the same regardless of where the load is applied In anisotropic the mechanical behavior of a structure is determined by the type of load (tensile, compressive, shear) and where the load is applied on the structure.

During osteoporosis, is bone formation or bone degradation more predominant?

In osteoporosis, bone degradation is more predominant. This is because osteoclasts are the predominant cell involved in degradation, while osteoblasts are involved in formation of bone. Additionally, osteoblasts will become more predominant in response to a bone taking on a load. This is because the bone is dynamic/metabolically active and load stimulates osteoblasts and thus bone formation.

What is the key difference in what occurs to a structure between the elastic and plastic regions?

In the elastic region, a structure can deform but then return to its original length. Past the yielding point in the plastic region, a structure suffers micro tears and will suffer too much deformation to the point it will not return to its original length.

In the plastic zone, will a tissue remain permanently deformed?

In the plastic zone a very avascular ligament it is very likely that the small fibers will not heal leaving it permanently deformed. However, if a extremely vascular ligament reaches the plastic zone and is able to heal, it can avoid permanent deformity.

What is the main additional concept that Utah's paradigm adds to Wolf's Law?

It agrees that mechanical factors guide biological mechanisms Adds that bone's tissue-level biological mechanisms also need non-mechanical factors that modulate but do not replace

What makes human tissue unique?

It can adapt to external stresses placed on it It is able to alter its form in response to external or functional demands (loads)

Why is specialized connective tissue different?

It contains minerals like calcium and phosphate which makes bone hard and rigid.

When looking at a Load - Deformation curve for a ligament, what does the slope indicate if it is more vertical?

It is indicative of the ligament being more stiff. It has a greater ability to absorb load than it does the ability to deform. Different mechanical and non-mechanical factors will come into play and have effects on the verticality of the elastic region for that particular ligament.

What component of a stress-strain curve separates ligaments and tendons from bones and cartilage?

Ligaments and tendons have a toe region at the begin of their curves. This is the segment that allows the wavy structure to straighten out and reveal it original length of the tissue.

What are the three types of connective tissue?

Loose CT, Dense CT, Specialized CT

If material A is has a steep stress-strain curve and material B has a less steep curve, which is more stiff? More deformable?

Material A is more stiff because the y-axis is the stress a material can take. Material B is more deformable because the x-axis is the strain a material can take.

What is the most important factor in a bone's health and density?

Mechanical forces/load and activity. More activity and load will increase bone density while immobilization will decrease bone density.

Which component of bone contributes to the Hard and Rigid characteristic?

Mineralized Molecules (Calcium and Phosphate) Especially Crystals of Hydroxyapatite

How does the viscosity of synovial fluid within the knee impact one's ability to resist compressive forces within the joint?

More viscosity less movement (greater friction) less hydrodynamic response.

If you have a tendon that enters the plastic region, is it a guarantee that the tendon will reach the fracture point and break/tear?

No it is not a guarantee that it will break. It will depend on if you let the tendon heal and recover from the excess stress & strain being applied to it. It also depends on the tendon type and if there is an actual ability for it to heal. This would be attributed to whether the vascularity is good or not. If it is not able to repair and you don't decrease the stress and strain, it will most likely remain in the plastic phase and increase the ability down the road that it may break/tear completely.

What is the difference between the plastic region and the elastic region on the load deformation curve?

On a load deformation curve, the elastic region is 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. The Plastic region on the load deformation curve is to the right of the elastic region. If a load is applied to a material and it enters the plastic region, microtears can develop in the material, and the material cannot return to its original length after the load is applied. The yield point is the point between the plastic and elastic region.

What is one variable osteoblasts are important for?

Osteoblasts and Osteoclasts perform Bone Remodeling -Osteoblasts (and Osteocytes) are essential to bone formation

What is one variable osteoclasts are responsible for?

Osteoblasts and Osteoclasts perform Bone Remodeling -Osteoclasts are essential to bone reabsorption

What happens during osteoporosis?

Osteoclast activity is greater than osteoblast activity, resulting in more bone remodeling than bone formation

What is happening at the cellular level when someone has osteoporosis?

Osteoclastic activity is exceeding osteoblastic activity. This explains the degradation of bone

What is Osteoporosis?

Osteoporosis is when osteoclastic activity in a bone exceeds osteoblastic activity making the bones more brittle

What is the biggest difference in the bone-load deformation curve from the ligaments stress-strain curve?

Steeper modulus of elasticity

Cortical bones are more _______ because they can adapt to more _______.

Stiff, Stress. Cortical bones are more stiff because they can take a higher load per unit area, in comparison to trabecular bones.

What is strain?

Strain is the amount of relative deformation caused by a load on a viscoelastic material.

What is the equation for mechanical stresses?

Stress = Force / Area

Explain the difference between stress and strain.

Stress is LOAD PER UNIT OF AREA Strain is the change of deformation caused by a load. This can be calculated by subtracting the new length/width of the structure by the original length/width, then dividing it by the original. (L2-L1)/L1. This is reported in percentage. In the stress-strain curve relationship, this will be the x-axis. Deformation, change in % LENGTH!

On a load-deformation curve what does the slope represent in terms of the tissue

The slope represents the stiffness of the tissue. The slope can also be used to find Young's modulus of elasticity. The steeper the slope modulus means the stiffer the tissue and resistance to elongation.

How is the slope (modulus of elasticity) of the load-deformation curve relate to the stiffness and deformation of the tissue?

The steeper the curve is, the stiffer the tissue. The less steep the curve is (the more horizontal the curve), the more deformed the tissue is.

Describe what differences may be seen in a bone stress-strain curve that is analyzing normal bone and osteoporotic bone:

The steepness of the curve reflects the stiffness that the bone possesses. The curve of normal bone is steeper than that of the osteoporotic bone, meaning normal bone is stiffer than osteoporotic bone. When osteoporotic and normal bone are acted on by the same amount of force, the osteoporotic bone will undergo greater displacement. The varying shapes of the curves and abilities to withstand displacement under load indicate the differences in the composition of the normal and osteoporotic bone. Variation in the osteoporotic bone curve can be due to the deteriorating composition of the material making up the bone (bone becoming more porous).

What role does vascularity play in ligaments when they are stretched passed the yield point into the plastic region?

The vascularity of a ligament will play a role in the healing potential it has. For example the MCL is more vascular compared to the ACL, meaning if the MCL stretches into the plastic region is has a higher chance to heal and return to the elastic region and go back to its original length. The ACL being avascular does not have this potential to heal back to its original form.

What is the yielding point in a load-deformation curve?

The yielding point is the transition between the elastic region and the plastic region.

What is the yielding point in the load-deformation curve?

The yielding point is the transition from the elastic region to the plastic region. If the stress passes the yielding point it crosses into the plastic region where microtears of the tissue will occur and if the load is removed the tissue will not return back to its original shape but rather be stretched.

At what point in the load-deformation curve does the transition between elastic and plastic occur?

The yielding point.

What is similar and different between Wolff's Law and Utah's Paradigm?

They both state that mechanical properties are needed to stimulate bone growth and remodeling. However, Utah's paradigm also state that we must consider non-mechanical properties, such as nutrition, in terms of modulating bone.

What is the similarity in bone strength and stiffness in cortical vs cancellous/trabecular bone?

They both withstand compressive forces more than tensile forces

What is one assumption we can always make about tissue?

Tissues adapt to functional demands They change their properties based on demands that need to be met The demands are loads

True or False: A structure with greater cross-sectional area can withstand more force with less deformation, when compared to a structure of the same length with less cross-sectional area.

True - Based on the mechanical stress equation (S = F/A), the greater the area that is present, the less stress exerted

A body structure like the ligaments or tendons can rapidly surpass the physiological region of its load/deformation curve and break.

True: A break can be generated from load, deformation, or both. With a large enough load or deformation, a structure can rapidly surpass its physiological region and reach its break point. (in comparison to a structure experiencing gradual load and deformation)

What properties do viscoelastic materials have?

Viscoelastic is the biomechanical property of having a TIME and RATE dependent behavior. This can be described using the creep deformation and stress relaxation curves.

How does the speed in which a load is applied affect the strain rate?

When a load is applied rapidly, a larger force is needed to deform the tissue than if the load was applied slowly

Boundary lubrication

a monolayer of lubricant made of lubricin molecules which prevents direct Surface to surface contact of bones.

Mixed lubrication

combination of boundary lubrication and thin fluid film lubrication.

What are the cellular components of Hyaline cartilage vs fibrocartilage?

hyaline cartilage: fibroblasts, chondroblasts, chondrocytes fibrocartilage: fibroblasts, fibrocytes, fibrochondrocytes

Utah's paradigm stated that the wolff's law was correct but that the balance of osteoblasts and osteoclasts also depended on _______.

non-mechanical/biological factors

Thin fluid fill lubrication

provides a greater separation of the joint surface.

What is hysteresis in viscoelastic materials?

the energy absorbed from the initial load that is lost once the material returns to its unloaded position.

In osteoporosis, is osteoblast or osteoclast activity greater?

the osteoclast activity exceeds the osteoblast activity.

What can the yield point best be defined as?

the point in which there is a transition between the elastic and plastic zone.