Biomechanics Week 2&3

Front 1

define kinetics

Back 1

the study of the action of forces

Front 2

define torque

Back 2

rotary effect of a force, synonymous with moment of force
Nm
force times the perpendicular distance from the forces line of action to the AOR

Front 3

what is the first law of motion

Back 3

law of intertia.. object in motion will remain at rest or an object at rest will stay at rest unless acted on by an outside force.

Front 4

what is the second law of motion

Back 4

(linear force)
force = mass times acceleration
(angular force)
torque = (mass moment of inertia)(angular acceleration

Front 5

what is the thrid low of motion

Back 5

for every action there is an equal and opposite reaction

Front 6

what forces act on the human body

Back 6

1. external forces (gravity, external loads, physical contact, reaction forces)
2. internal forces (active, passive)

Front 7

mass moment of inertia

Back 7

resistance to angular motion/change in motion

Front 8

anthropometry

Back 8

measurement of individuals
-center of mass
-point around which a body's weight is equally balanced in all directions
-point at which the weight vector acts
segment mass-can be expressed as percent of total body mass

Front 9

what is a shear vs. a compression/distraction force

Back 9

shear force: the component perpendicular to the joint surface, force that wants to pull the bone off of the joint
compression/distraction force: force that compresses the joints together or pulls them apart

Front 10

what are the different lever classes

Back 10

1st class = see saw
2nd class = wheel barrell (ankle)
3rd class = elbow joint

Front 11

what are the two types of joints?

Back 11

synarthroses
(fibrous like sutures in skull or cartilaginous like pubic symphesis)
diarthroses
(filled with synovial fluid, moderate to extreme movement)

Front 12

what elements are always associated with synovial joints

Back 12

synovial fluid (fxn to nourish tissues and reduce friction), articular cartilage (hayline cart covers ends of bones), joint capsule, synovial membrane, ligaments, blood vessels, and sensory nerves

also may include intra-articular discs or menisci (to absorb impact), peripheral labrum (extra cartilage extending outside of the joint), fat pads (btwn two layers of joint capsule to fill up joint capsule so dont need as much synovial fluid), bursa (soft tissue containing fluid to reduce friction), and synovial plicae (inflodings of synovial membrane to allow for further ROM)

Front 13

what are the main components of connectie tissue structure

Back 13

1. fibrous proteins (collage, elastin)
2. ground substance
3. cells (fibroblasts, chondrocytes, osteocytes)

Front 14

define anisotropy

Back 14

any material that doesnt have the same density or alignment throughout therefore properties depend on orientation of sample and direction of force or where you measure force

Front 15

stress

strain

Back 15

sigma = force over area OR force per unit area within a tissue, developed in response to an external load

epsilon = change in length over original length (a percentage of how much the length changed) OR the percentage change in deformation that occurs in response to an external load

Front 16

draw a stress strain plot

Back 16

strain along bottom, stress is along y axis

toe region = region where low force gibes alot of strain

elastic region: any increase in stress causes an equal amount of strain

plastic region: micro damage is occuring

tensile strength: amt of force needed to make this tendon break

Front 17

what is the relationship between slope of the stress strain curve and the type of material

Back 17

the higher the slope the more brittle the material is. the lower the slope the more plastic it is,

Front 18

modulus of elasticity

Back 18

linear slope of the stress strain graph. high modulus = high stress for specific strain = stiffer material or less stretchy

Front 19

poisson's ratio

Back 19

change in length is accompanied by change in diameter

Front 20

what is viscoelasticity

Back 20

takes longer to return to an original location after being stretched. dependent on rate of load and how long load is applied and how long it has been since a previous load

Front 21

creep

Back 21

an example of viscoelasticity

a progressive strain of a material when exposed to a constant load over time. creep is reversible.

Front 22

stress relaxation

Back 22

initial increase in stress but if length is kept the same for a period of time there is a gradual release of stress - also in stretching

Front 23

hysteresis

Back 23

when you relieve the load... apply the load, release ant it goes back but not back to where it was, E is lost in form of heat

Front 24

tendons versus ligaments

Back 24

tendons: highly parallel collagen arrangement to deal with a force in one direction. tendon is stiffer and stronger

ligaments: less parallel collagen arrangement to deal with force i more than one direction. has a higher strain than a ligament.

Front 25

paratenon

Back 25

loose CT, found in areas of high friction

Front 26

endotenon

Back 26

surrounding fibers of tendon, continuos with muscle CT (perimysium)

Front 27

epitenon

Back 27

surrounding the entire tendon

Front 28

myotendinous junction

Back 28

endotenon is continuous with perimysium, multiple invaginations, high surface area, prmary site ofmuscle injury because it is the interface of two mechanically different tissues

Front 29

osteotendinous/osteoligamentous junction

Back 29

endotenon continues into bone as sharpeys fivers, join to periosteum. four layer transitional zone. gradual transition between tissue of different stiffness

Front 30

energy stored

Back 30

is the area under the stress strain graph. stored energy until the tissue fails

Front 31

results of ligament injury

Back 31

disordered collagen, immature collagen (less x-links)
increased type three collagen
increased cellularity/vascularity
decreased cross sectional area
increased creep (more joint laxity more motion between bone, can lead to cartilate or bone injury)

Front 32

what factors affect mechanical characteristics of tendon/ligaments

Back 32

age
immobilization
clinical applications like steroids, diabetes, genetic syndromes