Definitions (Bones) Flashcards
What is Biomechanics?
The study of how mechanical principles influence a living organisms structure and movement.
What is distance?
Spatial separation of two or more points, or ‘change in position’ (m)
What is displacement?
Net change in position from start to finish (m)
What is speed?
Distance travelled / time (m.s-1)
What is velocity?
Change in position (displacement) over time (m.s-1)
What is acceleration?
Rate of change of speed (m.s-2)
What is mass?
Quantity of matter which a body contains (kg)
What is weight?
The force acting on an object due to gravity; Mass x acceleration due to gravity (N) where g = 9.81m.s-2
What is force?
A ‘push or pull’ resulting from contact between 2 objects (exception = gravity)
F = ma (N = kg.m.s-2) = rate of change of momentum;
What is moment (torque)?
M = F x distance (N.m); Torque is produced by a force acting at a distance from the centre of rotation (COR). Causes rotation.
What is moment arm?
Length of a line perpendicular to the force vector and the COR
What is internal moment?
Moment generated by internal forces i.e. from muscles, ligaments
What is external moment?
Moment generated by external forces e.g. gravity, weights
What is momentum?
mu (kg.m.s-1)
What is work?
Force required to move an object a certain distance W = F x d (J, joule)
What is energy?
Capacity to do work. J = N x m
What is power?
rate of work, work / time (watt, W = N.m.s-1 = J.s-1
What is statics?
Study of forces acting on a body at rest or moving with constant velocity.
i.e. when the body is in static equilibrium. Provides a simplified way of studying the forces acting on the body and joint mechanics.
What is kinematics?
(‘kinema’ = movement) describes the motion of objects with no reference to the mass of those objects nor the forces which cause the motion. (range of motion, velocity, acceleration)
What are kinetics (dynamics)?
(‘kinesis’ = to move) the study of motion and its causes (forces)
What is Newton’s First Law?
An object remains at rest (or continues moving at a constant velocity) unless acted upon by an unbalanced external force.
What is Newton’s Second Law?
If there is an unbalanced force acting on an object, it produces an acceleration in the direction of the force, directly proportional to the force (f=ma).
What is Newton’s Third Law?
For every action (force) there is a reaction (opposing force) of equal magnitude but in the opposite direction.
What is isotrophy?
Uniformity in all directions. Identical mechanical properties in all directions
What is anisotrophy?
Mechanical properties vary depending on the direction of applied force
What is tension?
(Verb); apply a force to stretch something; (noun); state of being stretched
What is compression?
Action of (verb), or being (noun) compressed (generally shortened)
What is shear?
Occurs when equal and opposite forces are applied to opposite side of an object
What is torsion?
Twisting of an object (generates a distribution of stress across a cross-section)
What is bending?
Deformation of an object when force(s) applied perpendicular to longitudinal axis
What is stress?
Force per unit area (N.m-2)
What is strain?
Change in dimension divided by original dimension (e.g. extension/starting length)
What is the modulus of elasticity?
Stress/Strain (pascals, Pa)
What is stiffness?
A structures resistance to deformation (N.mm-1)
What is compliance?
How much a structure deforms under load (mm.N-1)
What is elasticity?
The ability of a structure to return to its original condition once a deforming force is removed.
What is viscoelasticity?
Time-dependent material properties (those that have elastic and viscous properties)
What is creep?
The gradual elongation of a material when subjected to a constant load
What is (stress) relaxation?
The gradual reduction of stress exhibited when a material is subjected to a fixed strain
What is hysteresis?
The loss of energy in a single loading-unloading cycle due to a material’s viscoelastic behavior (expressed as a percentage of the energy used to deform the material).
What is Mechanotransduction?
- Mechanocoupling
- transduction of physical forces to a mechanical signal, which is sent to the sensor cells - Biochemical coupling
- mechanical signal is converted into a biochemical signal - Transmission of signal from sensor cell to effector ell
- Effector cell response
• Mechnical stimulation of specific pathways and genes can enhance proliferation and differentiation of osteoblasts
What is toe region?
where crimp is being removed, becoming less wavy.
What is elastic (linear) region?
slope = E (Pa), where material behaves elastically
What is yield point?
where permanent damage and non-linear behaviour starts
What is plastic region?
post yield point, ductile behaviour with damage
What is ultimate stress (strength)?
maximum stress (Pa) able to be supported
What is ultimate strain?
maximum deformation/original length
What is toughness?
area under curve, ‘resistance to failure’
What is the safety factor (strength of bone)?
A safety factor of 4 – 10 is common amongst biological structures, wherein the strength of the structure is many time stronger than it apparently needs to be. i.e. the expected maximum stresses on the skeletal element are only 10 – 25% of the Ultimate stress
What is periosteum?
Dense fibrous membrane covering the surfaces of bones, consisting of an outer fibrous layer and an inner cellular layer (cambium). The outer layer is composed mostly of collagen and contains nerve fibres that cause pain when the tissue is damaged
What is endosteum?
Theendosteum(plural endostea) is a thin vascular membrane of connective tissue that lines the inner surface of the bony tissue that forms the medullary cavity of long bones. Thisendostealsurface is usually resorbed during long periods of malnutrition, resulting in less cortical thickness
What is an osteon?
Eachosteonconsists of concentric layers, or lamellae, of compact bone tissue that surround a central canal, the haversian canal. The haversian canal contains the bone’s blood supplies.
What is lamella(e)?
Plates of collagen fibers, 3 to 7 µm thick, found in secondary (mature, adult)boneand surrounded by cementing substance, the mineralizedbonematrix. Somelamellaeare parallel to each other. Otherlamellaeare aligned concentrically around a vascular canal — a structure known as a haversian system or osteon.
What is cement line?
Thecement line, which is the interface between the ‘fibers’ (osteons) and extraosteonalbonematrix, may impart important mechanical properties to compactbone.
The boundary of an osteon is the cement line
What is central canal?
Thehaversian/centralcanal contains the bone’s blood supplies.
What are osteocytes?
A cell that lies within the substance of fully formed bone. It occupies a small chamber called a lacuna, which is contained in the calcified matrix of bone. Osteocytes derive from osteoblasts, or bone-forming cells, and are essentially osteoblasts surrounded by the products they secreted
