MSK 3 Flashcards
(219 cards)
what is a synovial joint
two (or more) articulating bones
ARTICULATING surfaces covered by HYALINE cartilage
enclosed fibrous capsule
NON-ARTICULATING surfaces lined by SYNOVIUM (synovial membrane)
joint space filled with synovial fluid
formed from condensing mesenchymal tissue–> interzonal mesenchyme (menisci, cruciate ligaments, synovium)
describe the structure of articular cartilage
- no perichondrium–> makes healing and nutrition difficult
- not innervated
- negligible friction
- chondrocytes make ALL the proteins–> type II collagen and proteoglycans
- formed by ARCHES–> the arches confer structural stability and ability to be compressed (weight bearing)
- mechanism of walking circulates and renews water content–> supplies nutrients and removes waste from joint
what are the two basic layers of the synovium
- superficial (cellular lamina) inner border
2. deep (subcellular intima)
what is found in the superficial/cellular lamina layer of the synovium
consists of SYNOVIOCYTES (which gives the impression of a cell membrane)
- lines inner surface of the synovium
- variable shapes
- 1-3 cell layers thick
- no intracellular junctions or basement membrane (therefore not true epithelium)
**there are two types of synoviocytes: A and B
what are the two types of synoviocytes and how do they differ
found in the superficial/cellular lamina layer of the synovium
A–> 20-30%; MONOCYTE derived–> phagocytose particles within the joint space, produce lytic enzymes; become macrophage-like synovial presenting (dendritic) cell in rheumatoid arthritis
B–> predominant; MESENCHYME derived–> synthesize and secrete lubricating molecules like hyaluronic acid and lubricin
what is found in the deep/subcellular intima layer of the synovium
vascular connective tissue (may be loose, fibrous or adipose)
what is the source of synovial fluid
2 sources: transudate of serum and secretion from type B synoviocytes
transudate is from fenestrated capillaries in the connective tissue of the synovium (excludes molecules > 100 nm)
what happens to the transudate portion of the synovial fluid during inflammation
during inflammation, capillaries become leaky and cell counts increase from 100/ml to >50 000/ml and EXUDATE
what is the meniscus composed of
fibrocartilage
mixture of dense regular CT and cartilage
type I collagen fibres in parallel
what is the purpose of the structure of the synovial joint? (i.e what function does it serve)
the presence of lubricating fluid and the capsule around the joint allow for a greater range of motion without friction
how do the synovial joint structures relate to one another during expansion (i.e not weight bearing)
- negative GAG side chains repel each other
- side chains attract water
- cartilage matrix volume increases
- matrix expansion is limited by the collagen arcade
how do the synovial joint structures relate to one another during compression (i.e weight bearing)
- weight bearing pushes GAG side chains together
- side chains release water
- reduces cartilage matrix volume
describe the consistency of synovial fluid
viscous
non-newtonian fluid with egg white consistency
what is the principle role of synovial fluid
reduce friction between articular cartilage during movement
what secretes synovial fluid
(some is transudate from fenestrated capillaries)
synovial membrane secretes synovial fluid in the joint cavity
what does synovial fluid contain
- hyaluronan–> secreted by fibroblast-like cells (type B synoviocytes)
- lubricin–> secreted by chondrocytes of the articular cartilage and type B synoviocytes
- interstitial fluid filtered from the blood plasma
in addition to reducing friction, what is another role of synovial fluid
also participates in nutrient and waste transportation
fluid supplies oxygen and nutrients and removes CO2
protects cartilage and other joint structures from stresses during loading
how does synovial fluid protect joint structures/cartilage during loading
it is a non-compressable fluid film trapped between articular surfaces during loading–> this is called molecular sieving
list the different types of synovial fluid
type 0–> normal
type 1–> non-inflammatory
type 2–> inflammatory
type 3–> septic
type 4–> hemorrhagic
describe the following attributes of type 0 (normal) synovial fluid
- volume
- viscosity
- clarity
- color
- WBC count
- polys (%)
- gram stain
- glucose
- protein
- crystals
for type 0 (normal)
- less than 3.5 ml
- high
- clear
- colorless/straw
- less than 200
- less than 25%
- negative
- normal
- normal (1/3 serum)
- none
describe the following attributes of type 1 (non-inflammatory) synovial fluid
- volume
- viscosity
- clarity
- color
- WBC count
- polys (%)
- gram stain
- glucose
- protein
- crystals
for type 1 (non-inflammatory)
- > 3.5 ml
- high viscosity
- clear
- straw/yellow color
- 200-2000 WBC/mm3 (mostly mononuclear)
- less than 25%
- negative
- normal
- normal (1/3 serum)
- none
describe the following attributes of type 2 (inflammatory) synovial fluid
- volume
- viscosity
- clarity
- color
- WBC count
- polys (%)
- gram stain
- glucose
- protein
- crystals
for type 2 (inflammatory)
- > 3.5 ml
- low viscosity
- cloudy
- yellow color
- 2000-75000 WBC/mm3 (mostly polyonuclear)
- > 50% polys
- gram stain negative
- decreased glucose
- increased protein
- positive for crystals if in the setting of gout; negative for crystals if in the setting of rheumatoid arthritis
describe the following attributes of type 3 (septic) synovial fluid
- volume
- viscosity
- clarity
- color
- WBC count
- polys (%)
- gram stain
- glucose
- protein
- crystals
for type 3 (septic)
- > 3.5 ml
- mixed viscosity
- opaque
- mixed color
- > 100 000 WBC/mm3
- > 75% polys
- gram stain often positive
- glucose is very decreased
- increased protein
- no crystals
describe the following attributes of type 4 (hemorrhagic) synovial fluid
- volume
- viscosity
- clarity
- color
- WBC count
- polys (%)
- gram stain
- glucose
- protein
- crystals
for type 4 (hemorrhagic)
- > 3.5 ml
- high viscosity
- mixed clarity
- red color
- > 100 000 WBCs/mm3
- > 75% polys
- negative gram stain
- normal glucose
- normal protein (1/3 serum)
- no crystals