MSK L5 Bone and Cartilage Flashcards Preview

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Flashcards in MSK L5 Bone and Cartilage Deck (57)
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1
Q

Matrix: Made up of

A

Inorganic/mineral

Organic

2
Q

Matrix: Inorganic/mineral made up of

A

Hydroxyapatite

3
Q

Matrix: Inorganic/mineral Function

A

Compression strength

→ without = bendy

4
Q

Matrix:Organic made up of

A

Collagen and proteoglycans

→ without =brittle bones (osteogenesis impracta

5
Q

Matrix: Organic part function

A

Flexible strength

6
Q

Bones types:

A
  1. Cortical or compact – more dense

2. Cancellous (trabecular or spongy) – less dense – bars and plates interconnected

7
Q

Matrix

A

Made up of many osteons

8
Q

Osteon

A

Concentric layers of lamellae around central blood vessels.

9
Q

Haversian canal

A

Contains blood vessels

10
Q

Interstial lamellae

A

In between two osteon

11
Q

Circumferential lamellae

A

Near matrix at surface

12
Q

Canaliculi

A

Radiate from lacunae from mature bones and osteocytes into the haversian canal. Channels provide passageway through compact bone to provide nutrition to the cells.

13
Q

Volkmann’s canal

A

Perforating blood vessels – allows them to join in outer membrane

14
Q

Osteoblast

A

Forming bone (multinucleated)

15
Q

Canaliculus

A

Radiate from lacunar of mature bone cell (osteocyte) into adjacent cavities with blood vessels to obtain nutrients.

16
Q

2 types of bone development (ossification):

A
  1. Intramembranous → ossification of membrane to bone

2. Endochondral ossification→ calcification of cartilage model into bone

17
Q

Bone Growth:

A

Apposition growth
Process (width)
Endochonral growth (length) process

18
Q

Apposition growth

Process (width)

A
  1. OB in periosteum secrete matrix and become trapped as osteocytes
  2. Osteoclasts in crease diameter of medullary cavity
  3. Increases diameter of bones until skeletal maturity
19
Q

Endochonral growth (length) process

A
  1. Requires interstitial growth from cartilage first
  2. Occurs at epiphyseal growth plates
  3. Stops when growth plates ossify
20
Q

New bone laid down

A

Woven bone (random collagen)

21
Q

Remodelled why

A

More orderly collagen fibres

22
Q

Remodelling process

A
Osteoblasts lay down bone
Osteoclasts resorbed (remove) bone
→ Lamellar bone (ordered formed)
23
Q

Mature bone

A

Old bone is constantly being replaced by new bone

Bone shape changes in response to changing stresses

24
Q

Factors influencing bone growth and remodelling:

A
  1. Mechanical factors
  2. Genes
  3. Hormones
  4. Aging
  5. Diseases
25
Q

Mechanical → influencing bone growth and remodelling:

A

Wolf’s Law
→ More stress increases osteoblasts activity → more bone
→ Less stress decreases osteoblast activity → less bone

26
Q

Genes: influencing bone growth and remodelling:

A
  1. Determine potential shape and size
  2. Height and bone mass is multifactorial (many genes involved and other factors)
  3. Genes influence
    a. Growth hormone release
    b. Hormone receptor on bone cells
    c. Ability to absorb nutrients from the gut
  4. Some genetic disorders influence bone growth e.g. dwarfism (FGFr3 mutation), turners syndrome
27
Q

Hormones: influencing bone growth and remodelling:

A
  1. Growth, sex and thyroid hormones influence cell differentiation and metabolism
  2. Overactive pituitary gland →excess GH
28
Q

Ageing: influencing bone growth and remodelling:

A
  1. Osteoblast matrix production slows in comparison to osteoclast matrix resorption
  2. Decreased collagen deposition results in more brittle bone (less flexible strength)
  3. Bone mass peaks at 25-30 years then falls.
29
Q

Diseases: influencing bone growth and remodelling:

A
  1. Osteoporosis → bone mass is reduced particularly in women after menopause (reduced oestrogen production).
  2. Other factors affecting oestrogen levels
    a. Removal of ovaries
    b. Extreme exercise
    c. Anorexia nervosa
    d. Smoking
  3. Cancellous bone is most affect as it is severly weakened if connections lost.
30
Q

FGFr3 →

A

normal proliferation of chondrocytes

Defective = poor proliferation of chondrocytes an abnormal growth of long bones in limb.

31
Q

Cartilage: types

A
  1. Fibrocartilage – strongest and most rigid
    a. E.g. minicus
  2. Hyaline cartilage
    a. Joint surface
    b. Epiphyseal growth plate
  3. Elastic cartilage → balance between structure and flexibility
    a. E.g. ear
    b. Eustacian tube
32
Q

Cartilage growth

A
  1. Appositional growth

2. Interstial growth

33
Q

Perichondrium: Outer layer

A

Dense irregular CT with fibroblasts

34
Q

Perichondrium: Inner layer

A

Fewer fibres with chondroblasts

35
Q

Perichondrium: Appositional growth

A

Chondroblasts

36
Q

Perichondrium: Interstial growth

A

Chondrocytes

37
Q

Articular Cartilage: Type of

A

Hyaline cartilage

38
Q

Articular Cartilage: Found

A

On articular surfaces of bones

39
Q

Articular Cartilage:Has no

A

Perichondrium- as it forms part of the joint.

40
Q

Articular Cartilage: Growth

A

Similar to growth plate (but never ossifies)

Columns of cells → calcified cartilage and then form bone

41
Q

Articular Cartilage: Collagen structure

A

Arcades – high concentration of collagen on the surface.

42
Q

Articular Cartilage: Arcades

A

Type II collagen fibrils anchor proteoglycan matrix to bone

43
Q

Articular Cartilage: Growth stops

A

At a similar time to growth plate but never ossifies

44
Q

Function of Articular cartilage: Smooth

A
  1. Reduces friction (heat → protein damage)

2. Low-wear surface

45
Q

Function of Articular cartilage: Deformable and elastic

A

Distributes load evenly
• Increased surface area → reduced force (peak contact stress)
• Creep (deformation and load) also increase surface area during sustained loading

46
Q

Function of Articular cartilage: Visually

A
  • Simple, inert tissue
  • Has high stiffness to compression and resilience
  • Exceptional ability to distribute load and great durability
47
Q

Function of Articular cartilage: Adult articular cartilage

A

Hypocellular
Aneural
Avascular

48
Q

Cartilage matrix

A
. Large number of proteoglycans attaching to hyaluronic acid chain → help to maintain the reversible deformity property of cartilage.
→ Maintains water within the structure
3.	Collagen type II (mainly)
a.	Provide stable structure
4.	Collagen (other types)
49
Q

Matrix Synthesis Promotion

A

TGF

IGF

50
Q

Matrix Synthesis Inhibition

A

IL-1

TNF

51
Q

Matrix degradation Promotion

A

IL-1

TNF

52
Q

Matrix degradation Inhibition

A

TGF

IGF

53
Q

Factors influencing cartilage metabolism

A
  1. Mechanical factors
  2. Injury
  3. Aging
  4. Diseases
54
Q

Mechanical → adaptive remodelling

A

Cartilage is poor at this
➢ High strain = deposition
➢ Low strain = resorption
1. Anabolic and catabolic processes adjusted to adapt matrix to mechanical demands.
2. Low below 1 MPa may be catabolic while load above 1 MPa may be a anabolic stimulus.

55
Q

Injury and repair:

A
  1. Lack capillaries within cartilage.
  2. Nutrients from diffusion (synovium not bone).
  3. Chondrocytes do not normally divide in adult but still secrete matrix (repairs normal wear).
  4. Tears/lesions never fully heal.
56
Q

Ageing:

A
  1. Decreased PG and collagen turnover
    a. Collagen disruption
    b. PGs lost
    c. Water lost on compression
    d. Tissue damage
  2. Increase no-enzymatic glycation NEG)
  3. Impaired joint lubrication
    a. Friction/heat
    b. Fibrillation
    c. Osteoarthritis
57
Q

Non-enzymatic glycation:

A
  1. Cross-linking between collagen and sugars
  2. Process not controlled by enzymes or cells
  3. Advanced glycatino end=products (AGEs) make tissue stiffer, more brittle and yellowish (seen with ageing)

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