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Flashcards in Basic science random facts Deck (44):
1

Fracture healing pizoelectric changes

compression side is electronegative and stimulates osteoblast formation

 

tension side is electropostive and simulates osteoclasts

2

Inflammation phase of fracture healing

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

3

Repair phase of fracture healing

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

4

The process of host repair following osteonecrosis is referred to as

creeping substitution

5

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

decreased tissue stiffness

6

Pacinian corpuscles 

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

7

Ruffini corpuscles

slowly adapting receptors that detect stretching of the skin

8

Meissner corpuscle

rapidly adapting sensory receptor, is very sensitive to touch

9

Merkel's skin receptors (disc)

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

10

Creep definition

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

11

load relaxation definition

decreased peak loads over time with the same amount of elongation

12

Plastic deformation definition

irreversible change in length after removing the load 

13

Fatigue

failure at a submaximal tensile strength after numerous loading cycles

14

Ultimate strength

Load at which a material fractures

15

anisotropic 

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

16

viscoelasticity

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

17

galvanic corrosion

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

18

yield strength (yield point)

the stress at which a material begins to undergo plastic deformation

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19

toughness

amount of energy a material can absorb before failure

20

Endurance limit 

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

21

Fretting 

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

22

Moduli of Elasticity (GPa)

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

etanercept (Enbrel) mechanism of action

TNF receptor - IgG1 fusion protein

24

infliximab (Remicade) mechanism of action

chimeric mouse/human monoclonal Ab to TNF

25

anakinra mechanism of action

recombinant IL1 receptor antagonist

26

rituximab mechanism of action

monoclonal Ab to CD20 antigen (B cell inhibition)

27

most common immunosuppressive agent in RA

leflunomide (inhibits T cells)

28

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

calcium chloride and thrombin

29

Tendon strength after repair

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

working length (distance) - plate

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31

working length - rod

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32

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

5% of the total weight

33

antibiotic that is bacteriostatic at therapeutic serum concentrations

clindamycin

(pen/ceph/vanc all bictericidal per AAOS)

34

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

 

 

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

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

Eikenella

36

Oral drug combo (synergistic) for MRSA

quinolone + rifampin

37

abx quick mech of action

  • 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

COX-2 facts (3)

- 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

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39

AA metabolism figure

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40

changes in structure and function with immobilization of TENDON

decreases tensile strength, stiffness, and total weight

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

41

muscle fiber types 1

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

oxazolidinone (linezolid) mech of action

inhibit protein synthesis 70S ribosomal subunit

43

aminoglycosides mech of action 

 disrupt protein synthesis, 30s ribosome subunit

44

Lyme's treatment

amoxicillin, doxycycline, or cefuroxime

4 weeks

oral abx generally ok