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Musculoskeletal System > 9. Cartilage of the Joint > Flashcards

9. Cartilage of the Joint Flashcards

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1
Q

what is CARTILAGE

A

specialized form of CONNECTIVE TISSUE that consists of CELLS and
EXTRACELLULAR MATERIAL

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2
Q

What do you find in CARTILAGE, EMBEDDED in ECM

A

CHONDROCYTES
- secrete extracellular material (mostly matrix proteins)

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3
Q

what gives the cartilage its unique characteristics

A

MATRIX

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4
Q

CARTILAGES are classified into: (3)

A
  • HYALINE CARTILAGE
    (mainly in Synovial Joints)
  • ELASTIC CARTILAGE
    (outer ear, larynx, epiglottis)
  • FIBROCARTILAGE
    weight-bearing
    (pubic symphysis, intervertebral discs, meniscus, and temporomandibular joint)
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5
Q

what do you find in ELASTIC CARTILAGE (in matrix)

A

ELASTIC FIBRES in matrix

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6
Q

what do you find in the MATRIX of FIBROUS CARTILAGE

A

COLLAGEN FIBRES

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7
Q

COMPONENTS of CARTILAGE (3)

A

COLLAGEN
ELASTIN
PROTEOGLYCAN

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8
Q

which COLLAGEN is the main one in CARTILAGE

A

TYPE 2

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9
Q

PURPOSE of COLLAGEN in CARTILAGE

A

provide structural STRENGTH

  • therefore type 2
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10
Q

PURPOSE of ELASTIN in CARTILAGE

A

FLEXIBILITY

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11
Q

PURPOSE of PROTEOGLYCAN in CARTILAGE

A

provides LARGE OSMOTIC EFFECT

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12
Q

how do PROTEOGLYCANS in CARTILAGE provide LARGE OSMOTIC EFFECT

A
  • they carry many NEGATIVE CHARGES
  • ATTRACT CATIONS (+) eg Na2+ SODIUM
  • resulting in LARGE OSMOTIC EFFECT which HOLDS WATER in the MATRIX (flow of water from the weak solution to the strong solution - WATER IN, enhances ability to BEAR LOAD)
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13
Q

What is a PROTEOGLYCAN

A
  • PROTEOGLYCANS consist of a core protein with at least one GLYCOSAMINOGLYCAN (GAG) COVALENTLY LINKED

Glycosaminoglycan: long
unbranched polysaccharide chains composed of repeating disaccharide units

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14
Q

EXAMPLE of a major PROTEOGLYCAN in CARTILAGE

A

AGGRECAN

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15
Q

what joint related substance is a NONSULFATED GLYCOSAMINOGLYCAN

A

HYALURONIC ACID

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16
Q

What is the MAIN FUNCTION of CARTILAGE

A

CONNECT BONES TOGETHER

(also found in the joints, the rib-cage, the ear, the nose, the throat and between the bones of the back)

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17
Q

another FUNCTION of CARTILAGE

A

create a place on which BONES CAN FORM when they are first developed
- growth plate

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18
Q

structure of the ECM of ELASTIC CARTILAGE

A

CRISS-CROSSED by numerous BRANCHED ELASTIC FIBRES - rich in ELASTIN (protein)

(see image)

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19
Q

ELASTIC FIBRES in ELASTIC CARTILAGE have a HIGH DEGREE OF FLEXIBILITY and RESILIENCE.
what % of their orginial length:

A

150% of ORIGINAL LENGTH

When bent, elastic cartilage will rapidly bounce back to its original form

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20
Q

what do you find on the OUTER MARGINS of ELASTIC CARTILAGE

A

fibrous PERICHONDRIUM

  • made of dense connective tissue (collagen secreted by FIBROBLASTS)
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21
Q

where is ELASTIC CARTILAGE MAINLY FOUND (3)

A
  • EXTERNAL EAR
  • EUSTACHIAN TUBES (opening that connects the middle ear with the nasal-sinus cavity)
  • epiglottis (flap of tissue that sits beneath the tongue at the back of the throat)
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22
Q

what does FIBROCARTILAGE compose of

A

TYPE I COLLAGEN
& FIBROUS TISSUE

viewed as a composite/mixture of HYALINE CARTILAGE
and DENSE FIBROUS CONNECTIVE TISSUE (COLLAGEN I)

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23
Q

what does FIBROCARTILAGE LACK

A

a true PERICHONDRIUM

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24
Q

FUNCTION of FIBROCARTILAGE
what sort of sites is it found at

A

WEIGHT-BEARING

at sites which are subjected to TENSILE and COMPRESSIVE FORCES

forms a structural and functional junction
where cartilage and ligament meet

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25
where is FIBROCARTILAGE FOUND
INTERVERTEBRAL DISCS MENISCI of KNEE (Lateral & Medial) TEMPOROMANDIBULAR JOINT
26
ARTICULAR CARTILAGE is which type of cartilage
HYALINE
27
2 FUNCTIONS of HYALINE CARTILAGE
- DISTRIBUTE LOAD (shock absorb) - ALLOW MOVEMENT
28
in HYALINE CARTILAGE, COLLAGEN TYPE II is ATTACHED to COLLAGEN TYPES..
9 IX & 11 XI
29
MATURE CHONDOCYTES (in hyaline and elastic cartilage) occupy spaces in the MATRIX called
LACUNA
30
2 CHARACTERISTICS of ARTICULAR CARTILAGE
AVASCULAR (no blood supply) ANEURAL (no nerves)
31
ARTICULAR CARTILAGE is..
SHOCK-ABSORBING
32
cells in the matrix of ARTICULAR CARTILAGE and what do they do
CHONDROCYTES maintain a stable phenotype to retain their function as a permanent cartilage
33
how are COLLAGEN FIBRES at SUPERFICICAL LAYER of ARTICULAR CARTILAGE vs DEEP LAYER
PARALLEL superficially STOOD ON THEIR ENDS at DEEP layer - collagen fibres most RESISTANT here
34
ARTICULAR CARTILAGE has DIFFERENT ZONES what does the TIDE MARK separate
CALCIFIED CARTILAGE (ZONE 4) (zones 1-3: Tangenital, Transitional, Radial)
35
PROTEOGLYCANS/AGGRECAN occupy LARGE VOLUME of WATER (due to NEGATIVE charge due to GLYCOSAMINOGLYCAN CHAINS attached). this brings about a RISE IN OSMOTIC PRESSURE and SWELLING of cartilage. HOW IS THIS HELD TOGETHER WHEN LOAD IS APPLIED?
RESISTANCE of COLLAGEN (intact collagen fibres) in cartilage COUNTERACTS SWELLING PRESURE and holds cartilage intact. these features enable joints to RESIST COMPRESSIVE FORCE while MAINTAINING a HIGH TENSILE STRENGTH
36
SYNOVIAL FLUID is important for articular cartilage function. what are its CHARACTERISTICS (4)
PLASMA-LIKE LUBRICATION to REDUCE FRICTION supplies NUTRITION (as no bloody supply)
37
COMPONENTS of SYNOVIAL FLUID
- LUBRICIN - PROTEOGLYCAN - HYALURONAN, HA (hyaluronica acid) - GLYCOSAMINOGLYCAN (composed of the repeating sugars glucuronic acid & N-acetylglucosamine.) - PHOSPOLIPIDS eg Phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin
38
LUBRICIN in SYNOVIAL FLUID (secreted by articular cartilage and synovium) is encoded by which GENE
PRG4
39
FUNCTION of HA in SYNOVIAL FLUID
PROVIDES VISCOSITY to synovial fluid (role in LUBRICATION) through its high molecular weight (0.5–3.8 106 Da) and concentration (0.1– 5mg/mL).
40
what do the PHOSPHOLIPIDS in SYNOVIAL FLUID provide
HYDROPHOBICITY to articular surface & lubrication for solid-solid contact
41
what is VISCOSITY a measure of
INTERNAL FRICTION of a FLUID
42
What is SHEAR
a strain produced by pressure in the structure of a substance the GREATER the FRICTION = the GREATER the FORCE NEEDED
43
VISCOSITY formula VISCOSITY =
SHEAR STRESS / SHEAR RATE SHEAR RATE: the measure of the FLUID SPEED compared to the SURFACE that its sliding from
44
SHEAR THINNING is derived from...as...
HA ALLIGNMENT MOLECULE as the SHEER RATE INCREASES movement of the alignment as as you move the joint
45
MODELS of LUBRICATION in ARTICULAR CARTILAGE: 1. SQUEEZE FILM:
as 2 surfaces are squeezed together, FLUID is SQUEEZED OUT from the gap generating a HYDROSTATIC PRESSURE
46
MODELS of LUBRICATION in ARTICULAR CARTILAGE: 2. BOOSTING/BOOSTED
eg if jumping WATER moves INTO cartilage and so INCREASES CONCENTRATION of HYALURONIC ACID in fluid-film
47
MODELS of LUBRICATION in ARTICULAR CARTILAGE: 3. ELASTOHYDRODYNAMIC
sliding MOVEMENT DEFORMATION of the surface serves to TRAP PRESSURIZED FLUID in 1 AREA
48
FLUID-FILM MECHANISMS
NO CONTACT between surfaces, FRICTION DEPENDENT on the VISCOSITY of the Lubricant PROVIDE the LOW FRICTION ENVIRONMENT for the articular cartilage at physiologic loads, accomplished by creating a wedge of fluid between the two bearing surfaces. The most desirable lubrication
49
BOUNDARY LUBRICATION
CHEMICAL PROPERTIES of Lubricant are NOT AS IMPORTANT as the SURFACES IN CONTACT PREVENTS ASHESION and ABRASIONS of two surface and is independent of the physical properties of the lubricant or contacting surfaces. Hyaluronan and lubricin are believed to be the main boundary lubricants of the diarthrodial joint.
50
what is the LAMBDA RATIO a measure of
MINIMUM FILM THICKNESS (h min) required in relation to the composite surface ROUGHNESS (Ra1, Ra2) shown on STIBECK CURVE friction coefficient against the bearing number μω/p (lubricant viscosity (η), speed (ω) and contact pressure (p) ) COEFFICIENT OF FRICTION is DIRECTLY PROPORTION to the VISCOSITY of the lubricant and the DIFFERENCE IN SPEED of the contact surfaces; and INVERSELY PROPORTIONAL to the PRESSURE which is EXERTED on the contact SURFACES *Boundary lubrication: λ ≤ 1 *Mixed lubrication: 1 < λ < 3 *Fluid film lubrication: λ ≥ 3
51
3 types of WEAR of articular cartilage which lead to DISRUPTION of CARTILAGE MICROSTRUCTURE
- INTERFACIAL WEAR Adhesion, Abrasion - FATIGUE WEAR increase strain rate, microtrauma exceed, reparative process - HIGH IMPACT LOADING WEAR increase Stress, Increase Strain
52
CHANGES in articular cartilage with WEAR:
- LOOSENING of COLLAGEN NETWORK - PROTEOGLYCAN EXPANSION (collagen not holding it together) - TISSUE SWELLING - REDUCED STIFFNESS of cartilage - INCREASED PERMEABILITY -> abnormal: STRESSED & STRAINS Mechanoelectrochemical stimuli ECM REMODELLING of CHONDROCYTES
53
what do the CHANGES in articular cartilage with WEAR eventually lead to
OSTEOARTHIRITIS
54
what is an EARLY INDICATOR of OSTEOARTHIRITIS
LOSS of PROTEOGLYCANS Formation of clusters of activated and proliferating chondrocytes is a hallmark in the early phase of OA cartilage
55
OA: what do CHONDROCYTES SECRETE that cause ARTICULAR CARTILAGE to be LOST what do they do
METZINCINS: MMPs & ADAMTSs ENZYMES that BREAK DOWN (/regulate) ECM
56
MMPs and ADAMTSs are part of which ENZYME FAMILY
METZINCINS
57
how many TYPES of MMPs and ADAMTSs are there
23 TYPES of MMPs 20 TYPES of ADAMTSs (19 types ADAMs)
58
OA: what ENZYME causes CLEAVAGE of COLLAGEN TYPE II (cleavage removes the collagen)
CATHEPSIN K - a lysosomal CYSTEIN PROTEASE (involved in bone remodelling and resorption)
59
OA: what do MMPs and ADAMTSs do to AGGRECAN (proteoglycan)
CLEAVE aggrecan (Aggrecanases - break down aggrecan)
60
OA: what results from CLEAVAGE of AGGRECAN by MMPs and ADAMTSs
AGGRECAN (proteoglycan) is LINKED to GLYCOSAMINOGLYCANS: - HYALURONAN (HA) - KERATAN SULFATE - CHONDROITIN SULFATE these sugars are RELEASED and escape CAUSING SWELLING
61
how does ARTICULAR CARTILAGE WITHSTAND LOAD
by ATTRACTING WATER into the NEGATIVELY CHARGED PROTEOGLYCANS

Musculoskeletal System (18 decks)

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