lecture 28-32: MSK 2 - joints

Question 1

joint definition

Answer 1

• any point where two or more bones interconnect
• movement
• force transmission
• growth

Question 2

functiona; joint classifications

Answer 2

• synarthrosis: immovable (commonaly axial)
• ampharthrosis: slightly movable
• diarthrosis: freely movable (commonly appendicular)

Question 3

simple synovial joint

Answer 3

• diarthrotic joint
• not restricted by properties of a specific tissue(s)
• ends are mostly free

Question 4

4 common feature sof synovial joints

Answer 4

1. articular cartilage
2. articular capsule - connects ends of joint (blood vessels and nerves)
3. joint cavity contains…
4. synovial fluid

Question 5

articular cartilage function

Answer 5

• covers ends of articulating bones
• hyaline cartilage
• absorbs shocks and support heavy loads
• smooth and near frictiones
  resit expansion, compression and shear

Question 6

articular cartilage structure

Answer 6

• surface: low PG, dense horizontal parralel fibres, oblong lacunae
• functional cartilage:
• increasing PG content
• middle zone: oblique pattern of fibres, round lacunae
• deepzone: verticle collagen, high PG, nests of chondrocytes
• transition zone: hydroxyapatite, calcifying chondrocyte
• osteochodral junction: very undulatory and rich in PG

Question 7

articular capsule function

Answer 7

• form sleeve around joint connecting bones
• perforated by cessels and nerves to suppy joint space.
• loose enough to not restrict movement but reinforced with ligaments

Question 8

articular capsule layers

Answer 8

• fibrous layer:
• synovial membrane:

Question 9

articular capsule fibrous layer

Answer 9

• dense connective tissue (regular and irregular)
• continuous with periostem
• resist tension and physical support to synovial membrane
• richly innervated (pain and proprio) and have fibroblasts

Question 10

articular capsule synovial membrane

Answer 10

• loose connective tissue
• intima: secrete componants if synovial fluid
• subintima: between fibrous and intima, highly vascular with adipocytes and fibroblasts
• capsule maintenance and protection

Question 11

articular capsule cells

Answer 11

• fibroblasts to lay down collagen and reticular and elastic fibres
• adipocytes in subintama
• macrophage sin subintama
• synovocytes that secrete fluid
• nerve cells

Question 12

joint cavity

Answer 12

• potential space with small amount fluid
• lines with synocial membrane with some infolding (villi)

Question 13

synovial fluid functions

Answer 13

• lubrication
• shock absorption
• chondrocyte metabolism

Question 14

synovial fluid componants

Answer 14

• contains water and Ca+, K+, Na+
• ultra filtrate of blood plasma
• some hyaluronic acid
• some free cells like monocytes and lymphocytes, macrophages

Question 15

structure of a proteoglycan complex

Answer 15

• repeating disaccharide = GAG (e.g chondroitin (CS), keratin sulphase (KS))
• attach multiple gags to core protein to make it a proteoglycan (e.g aggrecan)
• attach proteoglycans to another gag called hyaluronic acid to make large proteoglycan complex that attach to collagen fibres and are good at attracting water

Question 16

loading cycle/mechanism

Answer 16

1. -ve charges in middle cartilage zone attrract +ions from joint space into cartilage
2. increase ion conc. causes water movement into cartilage
3. unloaded equilibrium: cartilage swells until collagen tension forces prevent are equal to swelling forces
4. load introduced so water and +ions are squeezed back into joint space, but this also cushions load
5. loss of fluid decrease cartilage volume and -ve charges compressed closer together
6. compressive force becomes equally opposed by -ve charge repultion and solid componant
7. load removed and cycle repeats