MSK L3 Joint structure and function Flashcards Preview

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Flashcards in MSK L3 Joint structure and function Deck (102)
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1
Q

Classification of Joints:

A

According to structure

According to function

2
Q

Classification of Joints: According to structure

A
  1. Fibrous
  2. Cartilaginous
  3. Synovial
3
Q

Classification of Joints:

According to function

A

Synarthroses
Amphiarthroses
Diarthroses

4
Q
  1. Synarthroses
A

no/little movement (fibrous and some cartilaginous joints

5
Q
  1. Amphiarthroses
A

– some movement (cartilaginous joints)

6
Q
  1. Diarthroses
A

free movement (always synovial joints)

7
Q

Fibrous

A

no joint cavity and dense fibrous connective tissue joining articulating surface.

8
Q

Cartilaginous joints

A

no cavity and two bones are joined y pad of cartilage – fibrous or hyaline.

9
Q

Synovial –

A

cavity between ends of articulating bones – ends covered with fibrous or hyauline for protection.

10
Q

Fibrous Joints: 3 sub classifications:

A
  1. Sutures
  2. Syndesmoses
  3. Gomphoses
11
Q

Sutures

A

Found only in the skull,
Form at 18mths of age when they replace fontanels
Fibrous tissue covered by periosteum

12
Q

Several types of sutures

A
  1. Serrate (between frontal and parietal bones)
  2. Lap or squamous - overlap (between parietal and temporal bones
  3. Plane or butt (between paired maxillary bones forming hard palate).
13
Q

Synostosis sutures

A

Sutures may become totally ossified in adults forming a synostosis (e.g. between frontal bones)

14
Q

Syndesmoses:Definition

A

Bones joined by interosseous ligament or dense aponeurotic membrane

15
Q

Syndesmoses: Example

A

Interosseous membrane between radius and ulna

16
Q

Syndesmoses: Movement

A

Flexibility of collagen fibres in ligament may allow limited movement

17
Q

Gomphoses: Definition

A

Pegs and sockets, held in place by bundles of regular collagenous connective tissue

18
Q

Gomphoses: Example

A

Found between teeth and bones of jaw – periodontal ligaments

19
Q

Gomphoses:Movement

A

Allow sight movement of teeth during mastication as collagen fibres are orientated in different planes.

20
Q

Cartilaginous joints: types

A
  1. Synchondroses (primary)

2. Symphyses (secondary)

21
Q

Syncondroses (primary) Definition

A

Advancing centres of ossification separated by hyaline cartilage

22
Q

Syncondroses (primary) Temporary types

A

Most are temporary (e.g. epiphyseal growth plates (and fuse in adults

23
Q

Syncondroses (primary) Permanent types

A

Some persist throughout life e.g. costal cartilages, which allow some flexibility of rib cage during inspiration.

24
Q

Symphyses (secondary) Definition

A

Fibro-cartilage pads between a.c. of adjacenet bones

25
Q

Symphyses (secondary) Movement

A

Allow for slight movement: Symphysis pubis allows expansion of pelvis in childbirth.

26
Q

Symphyses (secondary)Examples

A

Symphysis pubis – childbirth

Intervertebral discs allow limied motion between vertebrae

27
Q

Symphyses (secondary)Examples that fuse

A

Some symphses fuse during growth (e.g. sacral and coccygeal discs)

28
Q

Synovial Joints: Definition

A

Articulating bones separated by synovial cavity filled with synovial fluid

29
Q

Synovial Joints: Movement

A

Cavity gives synovial joints wide range of movement compared to other joints

30
Q

Synovial Joints: Examples of movement in different planes

A
Plane (or gliding)
Hinge
Pivot
Ellipsode(or condyloid)
Saddle
Ball and socket
31
Q

Plane (gliding) joints: Definition

A

Opposing surfaces almost flat or slightly convex and concave

32
Q

Plane (gliding) joints: Allow

A

Small side0to-side or back-and-forth movements and small amount of rotation

33
Q

Plane (gliding) joints: Examples

A
  1. Sacroiliac joints
  2. Apopphyseal joints of spine
    • Allow thoracic sine ribs to movement upwards and outwards during inspiration
34
Q

Hinge joints → Definition

A

Convex and of one bone articulates with concave end of another.

35
Q

Hinge joints → Allow

A

Hinge-type movement about a single axis such as flexion and extension.

36
Q

Hinge joints →Examples

A

Interphalangeal joints of fingers, and tibio-femoral joint of knee.

37
Q

Pivot joints:Definition

A

Conical or rounded surface of one bone fits into depression on another.

38
Q

Pivot joints: Allows

A

Rotation about a single axis

39
Q

Pivot joints: v

A
  1. Joint between head of radius and ulnar allows rotation of forearm.
  2. Atlanto-axial joint between atlas and axis allows rotation of head.
40
Q

Ellipsoid:Definition

A

Oval convex surface articulates with ellipsoid concavity.

41
Q

Ellipsoid:Allows

A

Bi-axial movement in 2 planes but no rotation.

42
Q

Ellipsoid:Examples

A
  1. Atlanto-occipital joint in neck
  2. Meta-carpophalangeal (MCP) joints in hands
    Radiocarpal joint of wrist
43
Q

Saddle joints: Definition

A

Two saddle-shaped surfaces articulate at right angles to one another

44
Q

Saddle joints: Allows

A

Modified condyloid joint, allows wide range of movement about 2 axes

45
Q

Saddle joints:Examples

A

Found in carpometacarpal (CMC) joint of thumb, and in ankle.

46
Q

Ball and Socket Joints: Definition

A

Almost spherical head (ball) articulates with almost spherical cup (socket)

47
Q

Ball and Socket Joints:Movement

A

Allow for greatest range of movement of al joints, allow multi-axial movement in all planes

48
Q

Ball and Socket Joints: Examples

A

Hip and shoulder joints

49
Q
  1. All synovial joints are surround by
A

joint capsule which fully encloses articulating surfaces.

50
Q
  1. Joint capsule is lined by
A

synovium/synovial membrame – lines inner surface of joint capsule except where there is articular cartilage

51
Q
  1. Joint cavity – filled with
A

synovial fluid.

52
Q

Capsule

A

Outer fibrous capsule

Inner synovial membrane (synovium

53
Q

Outer fibrous capsule

A

Blends with periosteum

54
Q

Outer fibrous capsule composed of

A

Dense irregular connective

55
Q

Function of outer

A

Type 1 collagen – resists tensile loads as it is an irregular orientation – allows resistance of a range of mvoements

56
Q

Innervation of capsule

A

Highly innervated – site of joint pain rather than articular cartilage which has non blood supply or innervation.

57
Q

Inner capsule (syovium) Definition

A

Lines joint cavity except for articular surfaces

58
Q

Inner capsule (syovium) Functions

A

Produces constiuents of synovial fluid

59
Q

Ligaments: (within capsule) Formed from

A

Localised thickening of fibrous capsule

60
Q

Ligaments: (within capsule) Composed of

A

Denses REGULAR CT comprising parallel collagen fibres (mainly type 1)

61
Q

Function of collagen arrangement

A

Gives ligaments great tensile strength along their length

62
Q

Where synovium meets articular cartilage

A

Lots of infolding and villi
Villi → have many capillaries to ensure constituents e.g. oxygen and nutrients can transfer into the synovial fluid. Articualar (avascular) relies on this.

63
Q

2 main layers of synovium

A
  1. Supporting layer or stroma (sub0intima)

2. Lining of synovial cells in contact with synovial fluid

64
Q

2 types of synovial cell in inner lining

A
  1. Type A
65
Q

Type A cells
→ Derived from
→ Function

A

Derived form bone marrow (macrophages)
Secretory and phagocytic functions → high density of mito and golgi.
→ Remove cell debris from synovial fluid

66
Q

Type B cells
→Cell type
→ Function

A

Type of fibroblasts

Role in synthesis of hyaluronic acid (HA) and proteins → important for maintenance of viscosity (lubrication).

67
Q

Synovitis

A

Inflammation of synovium – symptom of RA

68
Q

Articular Cartilage: Contains

A

Cells, fibres and matrix arranged in zones

69
Q

Articular Cartilage: Zones

A
  1. Tangential zone
  2. Transitional zone
  3. Radial zone – column arrangement
  4. Calcified cartilage (by ossified bone)
70
Q

Articular Cartilage: Cartilage cells

A

Chondrocytes; density varies with age, morphology changes in different zones.

71
Q

Articular Cartilage: Fibres of Articular collagen

A

Fibres are collagen, mostly type II – resist stress

Small amount so type VI,IX,XI

72
Q

Articular Cartilage: Matrix composed of

A

Large aggregated proteoglycans (aggrecan) some smaller PGs (decorin and biglycan).

73
Q

Articular Cartilage: GAG side changed important for

A

Hydrophillic and therefore attract water into the cartilage – allows it to resist pressure and forces.

74
Q

Articular Cartilage: Surface of articular cartilage

A

Lamina splendens – covers articular surface

Provides a low friction surface

75
Q

Articular cartilage sits on

A

Subchondral bone

76
Q

Subchondral bone Definition

A

Cortical bone plate supported by trabecular bone

77
Q

Subchondral bone:In children

A

Perforated by blood vessels where it provides route for nutrient exchange, in adults it gathers nutrients from synovial fluid.

78
Q

Subchondral bone: In disease

A

Shows biochemical and structure changes in some joint diseases.

79
Q

Menisci: Definition

A

Articular discs or pads composed of fibro-cartilage

80
Q

Menisci: Located

A

Within capsule, provide extra strength and support

81
Q

Menisci: Greater contact area action

A

Increases stability and decreases stress on joint.

82
Q

Bursae: Definition

A

Flattened sacs filled with synovial fluid

83
Q

Bursae: Location

A

Often found where tendon passes over bone

84
Q

Bursae:Modified bursae

A

Form tendon sheaths that surround tendons

85
Q

Bursae: Inflammation

A

Bursitis can occur with overuse

86
Q

Synovial Fluid: Definition

A

Fills joint cavity and any bursae

87
Q

Synovial Fluid: Components

A

Similar to interstial fluid but contained high concentratinos of Hyalornic acid.

88
Q

Synovial Fluid: Hyalornic acid

A
Forms structure (longitudinal molelcus) GAG attach to to form aggregates.
Provides viscosity properties – helps with lubrication
89
Q

Synovial Fluid:Role

A
  1. Lubrication

2. Cartilage nutrition

90
Q

Mechanical Function of synovial joints:

A
  1. Synovial joints allow movement whilst providing stability
  2. Shape of articulating surfaces influences type and range of movement
  3. Increased mobility associated with reduced stability
91
Q

Improving stability:

A
  1. Bones enlarge at ends to provide large contact are (increased stability and reduced stress).
  2. Deformed cartilage and menisci also increase contact area
92
Q
  1. Stability further increased by:
A

a. Capsule and ligaments surrounding joint
b. Internal ligaments e.g. cruciates in knee – prevent forward and backward sliding
c. Attachment of muscles and tendons across joint.

93
Q

Mechanical function of cartilage:

A
  1. To protect bone from high stresses by distributing load evenly on to subchondral bone
  2. To provide low-friction low-wear surfaces (helped by presence of joint lubricants
94
Q

Role of mechanical factors in joint disorder: Shear causes friction leading to

A
  1. Loss of energy
  2. Increase in temperature
  3. Wear and tear at bearing surface
95
Q

Role of mechanical factors in joint disorder: Lubrication reduces

A

Damaging effects of friction

96
Q

Role of mechanical factors in joint disorder:In synovial joints, two main types of lubrication

A

Fluid-film

Boundary

97
Q

Fluid Film lubrication: Static compressive loading

A
  1. Load acting in centre
  2. Film of synovial fluid between two joint surfaces which acts to separate the surfaces
  3. Fluid will try to move laterally but because cartilage is deformable and permeable it spreads the load over a larger area leaving the film
  4. Fluid is also added
98
Q

Fluid Film lubrication: Dynamic loading e.g. walking

A

Hydrodynamic lubrication

  1. Fluid filled is dragged between the surfaces.
  2. At leading edge where cartilage is being loaded
  3. The fluid gets dragged between the two joint surfaces
99
Q

Fluid Film lubrication: Boundary lubrication

A

Lubricin – bound tightly to articular surface.

Charged molecules – like charged particles will repel eachother maintain a distance between the two surface

100
Q

Lubrication Failure:

A
  1. Failure of lubrication mechanisms can lead to increased friction and fibrillation of cartilage surface
  2. Roughened fibrillated surface results in increased friction and wear and may lead to further cartilage damage.
101
Q

Effects of sustained or repetitive loading:

A
  1. Mechanical loading causes fluid changes in cartilage, which are usually reversible
  2. Sustained compression squeezes fluid out, reducing cartilage thickness and ability to equalise stress on underlying bone.
  3. Repetitive cyclic loading can cause proteoglycan loss at cartilage surface and distortion of collagen network
102
Q

Effects of mechanical overload:

A
  1. High levels of mechanical loading can:
    a. Damage cartilage surface
    b. Kill chondrocytes

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