Basic science random facts Flashcards

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1
Q

Fracture healing pizoelectric changes

A

compression side is electronegative and stimulates osteoblast formation

tension side is electropostive and simulates osteoclasts

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2
Q

Inflammation phase of fracture healing

A

Hematoma –> Fibroblasts and mesenchymal migrate (granulation tissue) —> Osteoblasts and fibroblasts proliferate

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3
Q

Repair phase of fracture healing

A
Primary callus within two weeks --\>
 Enchondral ossification (woven bone) --\>
 Type II (+IV) collagen is produced early --\> type I collagen--\>
 Type X collagen types is expressed by hypertrophic chondrocytes as the extraarticular matrix undergoes calcification
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4
Q

The process of host repair following osteonecrosis is referred to as

A

creeping substitution

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5
Q

The application of 149 degree F (65 degree C) heat to collagen tissue immediately results in

A

decreased tissue stiffness

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6
Q

Pacinian corpuscles

A

ovoid in shape, measuring approximately 1 mm in length. They respond to high-frequency vibration and rapid indentations of the skin

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7
Q

Ruffini corpuscles

A

slowly adapting receptors that detect stretching of the skin

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8
Q

Meissner corpuscle

A

rapidly adapting sensory receptor, is very sensitive to touch

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9
Q

Merkel’s skin receptors (disc)

A

slowly adapting skin receptors that detect pressure (steady indentation), texture, and and can be appropriately evaluated by static two-point discrimination

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10
Q

Creep definition

A

progressive deformation of a material in response to a constant force over an extended period

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11
Q

load relaxation definition

A

decreased peak loads over time with the same amount of elongation

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12
Q

Plastic deformation definition

A

irreversible change in length after removing the load

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13
Q

Fatigue

A

failure at a submaximal tensile strength after numerous loading cycles

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14
Q

Ultimate strength

A

Load at which a material fractures

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15
Q

anisotropic

A

Change in mechanical properties as a result of the direction of a load

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16
Q

viscoelasticity

A

Change in the stress-strain relationship dependent on the rate of loading i

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17
Q

galvanic corrosion

A

corrosion resulting from an electrochemical potential created between two metals in conductive medium

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18
Q

yield strength (yield point)

A

the stress at which a material begins to undergo plastic deformation

19
Q

toughness

A

amount of energy a material can absorb before failure

20
Q

Endurance limit

A

maximum level of stress that can be applied to a material cyclically and never cause failure

21
Q

Fretting

A

physical movement (micro motion) of two plates against each other leading to mechanical wear and material transfer at the surface

22
Q

Moduli of Elasticity (GPa)

A

1) UHMWPE = 0.8-1.5.
* *2) Cancellous Bone = 2**
3) PMMA = 3.1

  • *4) Cortical Bone = 18**
    5) Titanium = 115
    6) Tantalum = 186
    7) Stainless Steel = 240

8) Cobalt-Chromium Alloy = 240
9) Zirconia (Ceramic) = 248
10) Alumina = 340

23
Q

etanercept (Enbrel) mechanism of action

A

TNF receptor - IgG1 fusion protein

24
Q

infliximab (Remicade) mechanism of action

A

chimeric mouse/human monoclonal Ab to TNF

25
Q

anakinra mechanism of action

A

recombinant IL1 receptor antagonist

26
Q

rituximab mechanism of action

A

monoclonal Ab to CD20 antigen (B cell inhibition)

27
Q

most common immunosuppressive agent in RA

A

leflunomide (inhibits T cells)

28
Q

initiates platelet activation and release of growth factors contained within the platelets

A

calcium chloride and thrombin

29
Q

Tendon strength after repair

A

weakest at 7-10 days

most of strength by 21-28 days

maximum strength at 6 months

  • final strength only reaches 2/3 of normal even years after repair
30
Q

working length (distance) - plate

A
31
Q

working length - rod

A
32
Q

maximal amount of antibiotic to be added to PMMA for optimizing antibiotic elution without deleterious effects on mechanical strength

A

5% of the total weight

33
Q

antibiotic that is bacteriostatic at therapeutic serum concentrations

A

clindamycin

(pen/ceph/vanc all bictericidal per AAOS)

34
Q

A brittle material such as a ceramic femoral head prosthesis undergoes what type(s) of deformation when loaded to failure?

A

Elastic!

Brittle materials undergo only fully recoverable (elastic) deformation prior to fracture. Brittle materials have little or no capacity to undergo permanent (plastic) deformation prior to fracture. The properties of brittle materials are neither temperature nor rate dependent (viscoelastic)

35
Q

most common bacterium found in an infection caused by a human bite

A

Eikenella

36
Q

Oral drug combo (synergistic) for MRSA

A

quinolone + rifampin

37
Q

abx quick mech of action

A
  • Beta-lactam antibiotics inhibit cell wall synthesis
  • Quinolones inhibit DNA gyrase
  • Aminoglycosides inhibit protein synthesis by binding to ribosomal RNA
  • Rifampin inhibits RNA synthesis
38
Q

COX-2 facts (3)

A
  • expressed at low levels unless it is induced by cytokines/inflammatory mediators, responsible for the upregulation of the inflammatory system
  • function to break down arachidonic acid into prostaglandins, thereby increasing their concentration at the site of injury under the influence of osteotropic factors such as TNF-alpha
  • KO mice problems with endochondral ossification
39
Q

AA metabolism figure

A
40
Q

changes in structure and function with immobilization of TENDON

A

decreases tensile strength, stiffness, and total weight

Microscopically, there is a decrease in cellularity, overall collagen organization, and collagen fibril diameter

41
Q

muscle fiber types 1

A

Type I muscle, also known as slow-twitch muscle, is responsible for aerobic, oxidative muscle metabolism. It has a much lower strength and speed of contraction than fast-twitch type II muscle but is significantly more fatigue resistant.

42
Q

oxazolidinone (linezolid) mech of action

A

inhibit protein synthesis 70S ribosomal subunit

43
Q

aminoglycosides mech of action

A

disrupt protein synthesis, 30s ribosome subunit

44
Q

Lyme’s treatment

A

amoxicillin, doxycycline, or cefuroxime

4 weeks

oral abx generally ok