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Third Year > MEC322: Skeletal System > Flashcards

MEC322: Skeletal System Flashcards

1
Q

What are the spatial subdivisions of the skeleton?

A

Axial skeleton

Appendicular skeleton

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2
Q

What components make up the skeletal system?

A

Bones (skeleton)
Joints
Cartilages
Ligaments

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3
Q

What are the functions of bones?

A
  • Support the body
  • Protect soft organs
    Skull and vertebrae protect brain and spinal cord
    Rib cage protects thoracic cavity organs
  • Attached skeletal muscles allow movement
  • Store minerals and fats
    Calcium and phosphorus
    Fat in the internal marrow cavity
  • Blood cell formation (hematopoiesis)
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4
Q

How many bones does an adult skeleton have?

A

206

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5
Q

Name the two basic types of bone tissue

A

compact bone

spongy bone

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6
Q

Describe compact bone

A

dense, smooth and homogeneous

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7
Q

Describe cancellous (spongy) bone

A

small needle-like pieces of bone

many open spaces

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8
Q

Name the four different types of bone shape and give an example of each

A

long bone
flat bone
short bone
irregular bone

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9
Q

Describe long bone

A 
Typically longer than they are wide
shaft with heads situated at both ends
contain mostly compact bone 
all bone in limbs are long bones (except wrist, ankle and kneecap)
examples: humerus
femur
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10
Q

Describe short bones

A

Generally cube-shaped
Contain mostly spongy bone
Include bones or wrist and ankle
Sesamoid bone are a type of short bone that form w/in tendons (patella)

examples: carpals
tarsals

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11
Q

Describe flat bones

A

Thin, flattened and usually curved
Two thin layers of compact bone surround a layer of spongy bone

Examples

  • skull
  • ribs
  • sternum
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12
Q

Describe irregular bones

A

Irregular shape
do not fit into other bone classification categories

Examples

  • vertebrae
  • hip bones
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13
Q

In a bones structure what is the diaphysis?

A
  • shaft
  • makes up most of bones length
  • composed of compact bone
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14
Q

What is the periosteum?

A

Outside covering of the diaphysis
Fibrous connective tissue membrane
Perforating (Sharpey’s) fibers secure periosteum to underlying bone

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15
Q

What is the epiphysis?

A

Ends of the bone

Composed mostly of spongy bone enclosed by thin layer of compact bone

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16
Q

What is the articular cartilage?

A

Covers external surface of the epiphyses
Made of hyaline cartilage
Decreases friction at joint surfaces

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17
Q

What is the epiphyseal plate?

A

Flat plate of hyaline cartilage seen in young, growing bone
Causes lengthwise growth of a long bone
fuses when growth stops

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18
Q

What is the epiphyseal line?

A

Remnant of the epiphyseal plate

Seen in adult bones

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19
Q

What is the marrow (medullary) cavity?

A

Cavity inside the shaft
Contains yellow marrow (mostly fat) in adults
Contains red marrow for blood cell formation in infants

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20
Q

In adults where is red marrow situated?

A

cavities of spongy bone and epiphyses of some long bones

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21
Q

What is the osteon (Haversian system)

?

A

Compact bone micro-anatomy

A unit of bone containing central canal and matrix rings

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22
Q

What is the cantral (haversian) canal?

A

Compact bone micro-anatomy
Opening in the center of an osteon
Runs lengthwise through bone
Carries blood vessels and nerves

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23
Q

Where are osteocytes situated?

A

Compact bone micro-anatomy

cavities called lacunae

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24
Q

How are lacunae arranged?

A

in concentric rings called lamellae

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25
Q

What are lamellae?

A

rings situated around the central (Haversian) canal

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26
Q

What is an osteocyte?

A

bone cell, maintains bone tissue

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27
Q

What is an osteoblast?

A

a cell which secretes the substance of bone

act in group

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28
Q

What is an osteoclast?

A

a large multinucleate bone cell which absorbs bone tissue during growth and healing.

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29
Q

What is the extracellular matrix of bone composed of?

A

Water
Collagen fibers and other organic molecules which provides bone its tensile strength
Crystallized mineral salts which gives bone its hardness

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30
Q

What is ossification?

A

Process of bone formation

Occurs on hyaline cartilage models or fibrous membranes

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31
Q

What is endochondral ossification?

A

Osteoblasts (bone-forming cells) cover hyaline cartilage model
Enclosed cartilage is digested away, opening up a medullary cavity

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32
Q

What are the two regions of long bone that are not converted from cartilage by birth? (they remain cartilage)

A

Articular cartilages
Epiphyseal plates
New cartilage is formed continuously on external face of these two cartilages
Old cartilage is broken down and replaced by bony matrix

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33
Q

What to factors dictate bone remodelling?

A

Blood calcium levels

Pull of gravity and muscles on the skeleton

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34
Q

When is parathyroid hormone release and what does it do?

A 
Released when blood calcium levels are low
Activates osteoclasts (bone-destroying cells)
Osteoclasts break down bone and release calcium ions into the blood
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35
Q

What does hypercalcemia prompt? and what is it?

A
  • calcium storage in bones

- high blood calcium levels

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36
Q

What is osteoporosis?

A

bone thinning disease
Disease makes bones fragile, and bones can easily fracture
Vertebral collapse results in kyphosis (also known as “dowager’s hump”)

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37
Q

Who is affected by osteoporosis?

A

50 percent of women over age 65

20 percent of men over age 70

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38
Q

How does estrogen aid in womens health?

A

Estrogen aids in health and normal density of a female skeleton

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39
Q

In mechanical terms what is the function of bone?

A

Provide mechanical support for each body segment

Act as a lever system to transfer muscle forces

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40
Q

What properties must bone have?

A

stiff, strong, tough and light

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41
Q

What do tension and compression lines do?

A

Help spread out load in bone

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42
Q

What two phases is bone made up of?

A

mineral (strong and brittle) & collagen (weak and ductile)

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43
Q

What does bone mechanics depend on?

A

types of loading

bone density

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44
Q

What types of loading can bone be put under?

A

tension - doesn’t work v well as naturally not subjected to tension a lot
compression
bending
torsion

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45
Q

If a bone deforms elastically what does that mean?

A

no permanent deformation

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46
Q

If a bone deforms plastically what does that mean?

A

permanent deformation

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47
Q

What is the yield point?

A

strain where plastic range begins

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48
Q

What is the ultimate strain/stress?

A

fracture occurs

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49
Q

Compare bone to a tendon under a load

A

bone has a higher Young’s modulus and UTS but a tendon is a lot more ductile and can undergo more strain

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50
Q

What strain are the tendons and bone put under when running?

A

Achilles tendon ~ 6% (Yield=8%)
Tibia ~ 0.07% (yield=0.7%)

tendons operate v close to their yield strength

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51
Q

Will bone break under tension, shear or compression first?

A

shear
tension
compression (Highest load)

52
Q

Torsion results in a….

A

spiral fracture

53
Q

Bending results in a….

A

butterfly fracture

54
Q

Compression results in a…

A

oblique fracture

55
Q

Tension results in a….

A

transverse fracture

56
Q

Does higher density make bone stiffer?

A

Yes
compact bone is the stiffest 1.8 g/cm^3
cancellous 0.3-0.9 g/cm^3

57
Q

How is strength of bone related to density?

A

strength ∝ 𝜌^2

58
Q

Describe fracture by single load/high stress

A

Tensile fractures usually induced by rigorous muscle contractions
Compression fractures induced by impacts
Most fractures involve bending, torsional, or combined loads

59
Q

Describe fracture by multiple loads/low stress

A 
fatigue fractures (stress fractures) 
no. of repetitions is important 
bone repairs during recovery after exercise
60
Q

How is bone remodelling dependent on mechanical loading? (mechanosensitive)

A

Wolff’s Law 1892
Bone laid down where needed
Resorbed where not needed

Bone response to loading is site specific, not general
Bone responds to high loads and impact loading
Trabecular bone lost most rapidly during unloading (bed rest, spaceflight etc.)

61
Q

describe fatigue injuries of tissue

A

Number of repetitions: Muscle fatigue increases stress on bones
Time between repetitions: Bone cannot repair rapidly enough

62
Q

What is the peak bone stress on anteromedial sufrace of tibia felt when running and walking?

A

Walk (1.4 m/s)
compression 2MPa
tension 3-4MPa

Running (2.2 m/s)
compression 3 MPa
tension 11-12MPa

63
Q

How is cancellous bone different to compact bone?

A

it is more porous

64
Q

What is the tensile strength of compact bone at 20 and 80yrs ?

A

20: 140MPa
80: 120MPa

65
Q

How does the bone age?

A

Higher porosity leads to higher loss in cancellous bone

Some changes in gross geometry

66
Q

How can exercise help bone ageing?

A

increase in bone density

higher bone mineral density

67
Q

What is a joint also know as?

A

articulation

68
Q

Describe a joint

A

a point of contact between bones, between cartilage and bones, or between teeth and bone

69
Q

What does a joints structure determine?

A

combination of strength and flexibility

70
Q

What two criteria is the structural classification of joints based on?

A

1) presence or absence of a space between the articulating bones, called a synovial cavity
2) type of connective tissue that holds the bones together.

71
Q

What are the three classifications of joints structurally?

A
  • fibrous joint
  • cartilaginous joint
  • synovial joint
72
Q

Describe a fibrous joint

A

no synovial cavity and bones are held together by dense irregular connective tissue.

Synarthrosis

73
Q

Describe a cartilaginous joint

A

no synovial cavity and the bones are held together by cartilage.

Amphiarthrosis
articulating bones tightly connected by either hyaline cartilage or fibrocartilage

74
Q

Describe a synovial joint

A

united by the dense irregular connective tissue of an articular capsule, and often by ligaments.

synovial cavity between articulating bones
Diarthrosis

75
Q

What does the functional classification of joint relate to?

A

degree of movement they permit

76
Q

Name the functional classification of joints?

A

Synarthrosis – An immovable joint.
Amphiarthrosis – A slightly movable joint.
Diarthrosis – A freely movable joint.

77
Q

What does the synovial membrane do?

A

secretes synovial fluid, which forms a thin, viscous film over the surfaces within the articular capsule. (envelope surrounding synovial joint)

78
Q

What do many synovial joints also contain?

A

accessory ligaments, articular discs, fibrous & synovial membranes.

79
Q

Name the types of synovial joint based on shape

A 
Plane joint
Hinge joint
Pivot joint
Condylar joint
Saddle joint
Ball-and-socket joint
80
Q

Movement of a plane joint

A

non-axial

bones in hand (palm)

81
Q

Movement of a hinge joint

A

uniaxial

elbow humerus and ulna

82
Q

Movement of a pivot joint

A

uniaxial

elbow ulna and radius

83
Q

Movement of a condylar joint

A

biaxial

finger metacarpal and phalanx

84
Q

Movement of a saddle joint

A

biaxial

finger carpal and metacarpal

85
Q

Movement of ball-and-socket

A

multiaxial

shoulder head of humerus

86
Q

What is tendonitis?

A

inflammation of tendon sheaths

87
Q

What is arthritis?

A

inflammation or degenerative disease of joints
over 100 types, most crippling widespread disease in US

initial symptoms: pain, stiffness, swelling of the joint

88
Q

Movement in the sagittal plane

A

flexion extension

89
Q

Movement in the coronal plane

A

lateral flexion

90
Q

Movement in the transverse plane

A

rotation of neck

internal external - shoulder and hip

91
Q

What is the function of the synovial joint?

A

Lubrication (no tangential forces)

Distribution of normal forces over a large area

92
Q

How is the function of the synovial joint achieved by synovial fluid and articular cartilage?

A

Both are biphasic (mixture of solid and fluid phases)
Synovial fluid: Fluid mixed with elastic solute aggregates
Cartilage: Elastic solid network inundated by fluid

93
Q

What biphasic mixture (colloid) is blood?

A

sol
solid in liquid

clotting blood is a gel
liquid in solid

94
Q

Define biocompatability

A

material the induces no measurable harm to the host

chemical and physical; interactions and design

95
Q

Give an example of a class I medical device

A

lowest risk

bandages, surgical scalpel

96
Q

Give an example of a class IIa medical device

A

Low risk

contact lenses, epidural catheter, pregnancy test

97
Q

Give an example of a class IIb medical device

A

Moderate risk

orthopaedic implants, dental implants, diagnostic ultrasound system

98
Q

Give an example of a class III medical device

A

High

HIV test kit, pacemaker, angioplasty catheter

99
Q

List the essential considerations made in design of metallic biomaterials

A 
Excellent biocompatibility (non-toxic)
High corrosion resistance
Suitable mechanical properties
High wear resistance
Osseo-integration (in the case of bone prosthetics)
100
Q

What guidance is given for biocompatibility?

A

Match elements that are present in body
Trace elements can be toxic at higher levels
No metals are completely inert or non-toxic
Use alloys with virtually inert element
Use highly corrosion resistant element (e.g. Ti)

101
Q

What guidance is given for corrosion resistance?

A

The body environment is very different from ambient conditions
Different part of the body have different pH and oxygen concentration
Normal pH: 7.2-7.4 but 3-4 at inflammation sites
Lower oxygen accelerates corrosion of metal

102
Q

What guidance is given for mechanical properties?

A

Materials must be able to match original tissue
Metals are able to bear significant loads and undergo plastic deformation prior to failure
Higher elastic modulus: implant will bear all load
Stress shielding effect
More exposure to cyclic loading
Normal walk: 1000s steps at 1Hz
At hip, loading stress ~50MPa
For a person that walks 2000 steps/day: 1x107 cycles !

103
Q

What guidance is given for wear?

A

Wear is inevitable in joints ⇒ Material choice dictated by joint type

104
Q

Which is the best pair of materials for ball and socket joints?

A

ceramic on ceramic

105
Q

What guidance is given for Osseo-integration?

A

For bone prosthetics:
Ability of an implant surface to bond to adjacent bone
Failed osseo-integration creates fibrous tissue, which leads to loosening
Modulated by surface properties (chemistry, roughness and topography)

106
Q

Why might iron be/not be biocompatible?

A

found in blood, necessary for proper function

too much can create free radicals

107
Q

Why might chromium be/not be biocompatible?

A

Regulator of sugar levels in body

High levels lead to DNA damage and liver toxicity

108
Q

Why might nickel be/not be biocompatible?

A

Involved in many functions (unknown until 1970s)

High levels is toxic to cells in-vitro and in animal studies

109
Q

List these alloys of steel in decreasing toxicity: nickel, cobalt, iron, vanadium titanium, chromium

A

cobalt, vanadium, nickel, chromium, titanium, iron (least toxic)

110
Q

Name the mechanical properties of 316L steel (good biocompatibility)

A

depends on alloy & processing
stronger than bone
but commonly fails as implant
fatigue strength in salone solution ~200-300MPa

111
Q

How do stainless steel implants fail?

A

fatigue

due to poor machining

112
Q

What need to be developed before iron-less stainless steel can be used?

A

toughening method

113
Q

Why are steel implant popular?

A 
Readily available
Lower cost
Excellent fabrication properties
Accepted biocompatibility
Toughness
114
Q

How is cobalt based alloys better than stainless steel?

A

better corrosion resistance

less toxic

115
Q

Why might cobalt be/not be biocompatible?

A

constituent of B12

At high level: heart damage

116
Q

Why might molybdenum be/not be biocompatible?

A

essential for many enzymes

no acute toxicity

117
Q

Why might tungsten be/not be biocompatible?

A

no role in human body found yet

no clear toxicity levels

118
Q

What do metal on metal implants lead to?

A

elevated serum metal ion levels

119
Q

How do the mechanical properties of the cobalt alloy compare to stainless steel?

A

Better mechanical properties due to packed crystal structure
Cobalt-Chromium yield strength > 500 MPa

Fatigue properties
Higher than stainless steel
Under physiological conditions, with 107 cycles, corrosion fatigue strength is below 200 MPa
No better than stainless steel after 20 years …..

120
Q

What is a cobalt based alloy most popular for?

A

implant for joint bearing system

121
Q

How are titanium implants superior

A

specific strength (strength/density)
Biocompatibility
Enhanced corrosion resistance
excellent bone bonding capabilities

122
Q

How are titanium implants inferior

A

Inferior in tribological properties
poor shear strength
wear resistance

123
Q

Why might titanium be/not be biocompatible?

A

not found in humans

non toxic even in large dose

124
Q

Why might vanadium be/not be biocompatible?

A

role not well defined in humans

could be toxic in large dose

125
Q

Why might aluminium be/not be biocompatible?

A 
function not well known in humans
causes neurological disease at large dose
126
Q

Why might niobium be/not be biocompatible?

A 
function not well known in humans
very toxic at large does, DNA damage
127
Q

Compare titanium to cobalt and steel

A

UTS comparable to stainless steel but lower than cobalt
same with yield strength
higher fatigue strength than ss but lower than cobalt

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