Lecture 2 Flashcards
What are the axes of human movement?
Around x axis: flexion, extension
Around z axis: abduction, adduction
Around y axis: medial/lateral rotation
What are synarthroses?
Joints with little movement.
Types include synostoses, synchondroses, and syndesmoses.
What are synostoses?
Bone-bone joints, such as sutures in the skull.
What are synchondroses?
Bone-cartilage-bone joints, such as the rib and sternum.
What are syndesmoses?
Bone-fibrous connective tissue-bone joints.
What are diarthroses?
Joints with a lot of movement.
What are synovial joints?
Joints that include articular cartilage, synovial fluid, synovial membrane, joint capsule, and ligaments.
What movements do synovial joints perform?
Spin, roll/rotation, glide.
What are uniaxial joints?
Joints that allow movement around one axis, such as hinge and pivot joints.
What is a hinge joint?
A uniaxial joint with a convex surface fitting into another convex surface.
What is a pivot joint?
A uniaxial joint allowing bone rotation on another bone.
What are biaxial joints?
Joints that allow movement around two axes, such as condyloid, ellipsoid, and saddle joints.
What is a condyloid joint?
A biaxial joint with a spherical convex surface fitting into a shallow concave surface.
What is an ellipsoid joint?
A biaxial joint with a flat convex surface and a deep concave surface.
What is a saddle joint?
A biaxial joint where convex and concave surfaces fit together like a saddle.
What are triaxial joints?
Joints that allow movement around three axes, such as ball and socket joints.
What is a ball and socket joint?
A triaxial joint where a spherical head fits into a concave depression.
What is a gliding/plane joint?
A joint with articular surfaces that slide on each other, allowing no rotation.
What is the Convex-Concave rule?
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.
What is the radius of curvature?
Amount of curvature of a joint surface; length of radius of a circle of the same curvature.
What characterizes the Closed Packed Position?
Joint has maximum area of surface contact, ligaments are under tension, capsule is taut/stretched, and joint is compressed.
What characterizes the Open Packed Position?
Joint surfaces are incongruent, ligaments are more slack, capsule is more slack, and there is greater ease for accessory movement.
What is Joint End Feel?
Resistance to movement at the end of passive joint range of motion.
What are the types of Joint End Feel?
Hard end feel (bone-bone), soft end feel (soft tissue), empty end feel (cannot reach end point = ligament rupture).
What is stress in mechanical properties?
Force to deform a structure, perpendicular to the area.
sigma = F/A where F = applied force, A = area over which force applied.
What are the types of forces?
Compression, tension, shear (force parallel instead of perpendicular to area).
What is strain?
Resulting deformation of a material from force; change in length of material.
epsilon = delta(L)/L where delta L is change in length of structure and L is resting length of structure.
What is the Toe region in the stress-strain curve?
Initial un-crimping of fibres.
What is the Elastic region in the stress-strain curve?
Material returns to original length when load is removed (linear).
What does the slope in the stress-strain curve represent?
Young’s elasticity modulus (E); higher E indicates a stiffer material.
What is the Plastic region in the stress-strain curve?
Structure does not return to original length when load is removed.
What is failure in materials?
Applied force continues beyond the plastic region.
What is the yield point?
The elastic limit, the point where material permanently deforms.
What is the failure point?
The ultimate strength, the largest stress a material withstands before failure.
What characterizes a ductile material?
Deforms plastically before failure.
What characterizes a brittle material?
Fails before plastic deformation.
What is Poisson’s ratio?
Lateral strain vs axial strain.
How is Poisson’s ratio calculated?
v = -lateral strain/axial strain.
What happens to a material when it is stretched?
Material is stretched in length but diameter gets wider (lateral strain).
What is fatigue in materials?
Loading cycles a material can withstand before failing (at a given load).
What is fatigue life?
The number of loading cycles.
What happens to materials under high loading rates?
They will fail at a stress lower than their ultimate strength.
What is viscoelastic behavior?
Time dependent mechanical behavior due to fluid-like component.
What is viscosity?
The gooeyness of material; high viscosity fluid flows more slowly.
What is creep?
Continued deformation over time as material is subjected to constant load.
What is stress relaxation?
The reduction of stress over time as material is subject to constant deformation.
What is bending in materials?
Tensile + compressive stress.
What is the neutral axis?
Location where there is zero stress.
What occurs on either side of the neutral axis?
Compression on one side and tension on the other side.
What is torsion?
A twisting force.
What does torsion generate?
Shear stress distributed across the structure.
What type of fracture is described as tension?
Transverse fracture.
What type of fracture is associated with compression?
Oblique fracture.
What type of fracture is caused by bending?
Butterfly fracture.
What type of fracture results from torsion?
Spiral fracture.
What is an isotropic material?
A material that does not depend on the direction of force.
What is an anisotropic material?
A material that depends on the direction of loading.
