Lecture 2

Question 1

What are the axes of human movement?

Answer 1

Around x axis: flexion, extension
Around z axis: abduction, adduction
Around y axis: medial/lateral rotation

Question 2

What are synarthroses?

Answer 2

Joints with little movement.

Types include synostoses, synchondroses, and syndesmoses.

Question 3

What are synostoses?

Answer 3

Bone-bone joints, such as sutures in the skull.

Question 4

What are synchondroses?

Answer 4

Bone-cartilage-bone joints, such as the rib and sternum.

Question 5

What are syndesmoses?

Answer 5

Bone-fibrous connective tissue-bone joints.

Question 6

What are diarthroses?

Answer 6

Joints with a lot of movement.

Question 7

What are synovial joints?

Answer 7

Joints that include articular cartilage, synovial fluid, synovial membrane, joint capsule, and ligaments.

Question 8

What movements do synovial joints perform?

Answer 8

Spin, roll/rotation, glide.

Question 9

What are uniaxial joints?

Answer 9

Joints that allow movement around one axis, such as hinge and pivot joints.

Question 10

What is a hinge joint?

Answer 10

A uniaxial joint with a convex surface fitting into another convex surface.

Question 11

What is a pivot joint?

Answer 11

A uniaxial joint allowing bone rotation on another bone.

Question 12

What are biaxial joints?

Answer 12

Joints that allow movement around two axes, such as condyloid, ellipsoid, and saddle joints.

Question 13

What is a condyloid joint?

Answer 13

A biaxial joint with a spherical convex surface fitting into a shallow concave surface.

Question 14

What is an ellipsoid joint?

Answer 14

A biaxial joint with a flat convex surface and a deep concave surface.

Question 15

What is a saddle joint?

Answer 15

A biaxial joint where convex and concave surfaces fit together like a saddle.

Question 16

What are triaxial joints?

Answer 16

Joints that allow movement around three axes, such as ball and socket joints.

Question 17

What is a ball and socket joint?

Answer 17

A triaxial joint where a spherical head fits into a concave depression.

Question 18

What is a gliding/plane joint?

Answer 18

A joint with articular surfaces that slide on each other, allowing no rotation.

Question 19

What is the Convex-Concave rule?

Answer 19

If the concave surface moves on the convex, it glides in the same direction as the bone segment’s roll. If the convex moves on the concave, it glides in the opposite direction of the bone rolling.

Question 20

What is the radius of curvature?

Answer 20

Amount of curvature of a joint surface; length of radius of a circle of the same curvature.

Question 21

What characterizes the Closed Packed Position?

Answer 21

Joint has maximum area of surface contact, ligaments are under tension, capsule is taut/stretched, and joint is compressed.

Question 22

What characterizes the Open Packed Position?

Answer 22

Joint surfaces are incongruent, ligaments are more slack, capsule is more slack, and there is greater ease for accessory movement.

Question 23

What is Joint End Feel?

Answer 23

Resistance to movement at the end of passive joint range of motion.

Question 24

What are the types of Joint End Feel?

Answer 24

Hard end feel (bone-bone), soft end feel (soft tissue), empty end feel (cannot reach end point = ligament rupture).

Question 25

What is stress in mechanical properties?

Answer 25

Force to deform a structure, perpendicular to the area. ## Footnote sigma = F/A where F = applied force, A = area over which force applied.

Question 26

What are the types of forces?

Answer 26

Compression, tension, shear (force parallel instead of perpendicular to area).

Question 27

What is strain?

Answer 27

Resulting deformation of a material from force; change in length of material. ## Footnote epsilon = delta(L)/L where delta L is change in length of structure and L is resting length of structure.

Question 28

What is the Toe region in the stress-strain curve?

Answer 28

Initial un-crimping of fibres.

Question 29

What is the Elastic region in the stress-strain curve?

Answer 29

Material returns to original length when load is removed (linear).

Question 30

What does the slope in the stress-strain curve represent?

Answer 30

Young's elasticity modulus (E); higher E indicates a stiffer material.

Question 31

What is the Plastic region in the stress-strain curve?

Answer 31

Structure does not return to original length when load is removed.

Question 33

What is failure in materials?

Answer 33

Applied force continues beyond the plastic region.

Question 34

What is the yield point?

Answer 34

The elastic limit, the point where material permanently deforms.

Question 35

What is the failure point?

Answer 35

The ultimate strength, the largest stress a material withstands before failure.

Question 36

What characterizes a ductile material?

Answer 36

Deforms plastically before failure.

Question 37

What characterizes a brittle material?

Answer 37

Fails before plastic deformation.

Question 38

What is Poisson's ratio?

Answer 38

Lateral strain vs axial strain.

Question 39

How is Poisson's ratio calculated?

Answer 39

v = -lateral strain/axial strain.

Question 40

What happens to a material when it is stretched?

Answer 40

Material is stretched in length but diameter gets wider (lateral strain).

Question 41

What is fatigue in materials?

Answer 41

Loading cycles a material can withstand before failing (at a given load).

Question 42

What is fatigue life?

Answer 42

The number of loading cycles.

Question 43

What happens to materials under high loading rates?

Answer 43

They will fail at a stress lower than their ultimate strength.

Question 44

What is viscoelastic behavior?

Answer 44

Time dependent mechanical behavior due to fluid-like component.

Question 45

What is viscosity?

Answer 45

The gooeyness of material; high viscosity fluid flows more slowly.

Question 46

What is creep?

Answer 46

Continued deformation over time as material is subjected to constant load.

Question 47

What is stress relaxation?

Answer 47

The reduction of stress over time as material is subject to constant deformation.

Question 48

What is bending in materials?

Answer 48

Tensile + compressive stress.

Question 49

What is the neutral axis?

Answer 49

Location where there is zero stress.

Question 50

What occurs on either side of the neutral axis?

Answer 50

Compression on one side and tension on the other side.

Question 51

What is torsion?

Answer 51

A twisting force.

Question 52

What does torsion generate?

Answer 52

Shear stress distributed across the structure.

Question 53

What type of fracture is described as tension?

Answer 53

Transverse fracture.

Question 54

What type of fracture is associated with compression?

Answer 54

Oblique fracture.

Question 55

What type of fracture is caused by bending?

Answer 55

Butterfly fracture.

Question 56

What type of fracture results from torsion?

Answer 56

Spiral fracture.

Question 57

What is an isotropic material?

Answer 57

A material that does not depend on the direction of force.

Question 58

What is an anisotropic material?

Answer 58

A material that depends on the direction of loading.