joints Flashcards
3 main categories of joints
fibrous, cartilaginous, synovial
3 types of fibrous joints
suture, syndesmosis, gomphosis
fibrous joints
held together by fibrous connective tissue, little movement
short, direct and often transitory
no joint cavity
suture joints (fibrous joint)
- flat bones of skull
- little movement but allow for growth
- close to form synostosis: fusion or 2 or more bones of skull
bregma
- meeting of sagittal and coronal suture on top of head (hole on head)
- also known as fontanelle
- persists in toy breeds; hole never closes up
syndesmosis joints (fibrous joint)
- intervening tissue; two adjacent bones linked together for example tibia and fibula
- more movement than suture but very restricted
gomphosis (fibrous joint)
- peg in a socket joint
- usually teeth
- firm attachment
- very slight movement
cartilaginous joints formed from
cartilage, fibro-cartilage or both
- no joint capsule
2 types of cartilaginous joints
- symphysis (fibrocartilaginous)
- synchondrosis (hyaline cartilage)
cartilaginous joints movement
limited; compression or stretching
symphysis (cartilaginous joint)
- fibrocartilaginous
- fibre sandwich between two layers of cartilage
- ex where 2 os coxae come together
- ex intervertebral disc
intervertebral disc joints
- in between vertebrae, fibres arranged in circular fashion like an onion, annulus fibrosum
- in the middle of disk is nucleus pulposus which is a gelatinous material
- slipped disk is rupture of annulus and nucleus pulposus spits out; puts pressure on spinal cord
synchondrosis joint (cartilaginous)
- hyaline cartilage
- mainly transitory joints in growing bones
- ex is epiphyseal cartilage aka growth plate
- ex is costochondral joint (rib to sternum)
- ex hyoid to skull
synovial joints all have
- joint capsule
- joint cavity
- synovial fluid (fills joint cavity)
- articular cartilage
classification of joints (simple and compound)
- simple: 2 articular surfaces
- compound; more than 2
ball and socket joint
enarthrosis
ex hip and shoulder
hinge joint
(ginglymus)
flex and extends, no lateral movement
condylar joint
ex stifle
condyles on condyles
flex and extend, no lateral movement
looks unstable, requires ligaments
pivot joint
trochoid
ex atlanto-axial
get rotation around a long axis
gliding joint
arthrodial
anything that doesn’t fit into above categories
ex is carpometacarpals joints
outer layer of joint capsule
stratum fibrosum
inner layer of joint capsule
what does it do
- stratum synoviale
- loose connective tissue; very thin, only 2-3 cells thick
- phagocytic: cells will engulf any tissue/ rubbish in synoviale fluid and removed
- cells also secrete things such as hyaluronan which gives synoviale fluid is viscous sticky character
stratum fibrosum (outer layer of joint capsule) + stratum synoviale (inner layer of joint capsule) =
synovial membrane
synovial membrane is
- secretory
- also absorptive (keeps right amount of synovial fluid in the joint) aided by movement –> lack of movement in old people = swollen joints bc too much synovial fluid
- other characteristics include folds, pouches and fat pads
articular cartilage is usually composed of
hyaline cartilage
but fibrocartilage in temporo-mandibular joint
function of articular cartilage
reduce friction and shock absorption
avascular and no nerves
articular cartilage get nutrition from
synovial membrane and some from underlying bone
how is articular cartilage regenerated
multiplication of healthy cartilage cells and by conversion of stratum synoviale cells
best regeneration at periphery because nearer nutrients from synovial membrane
thickness of cartilage depends on
weight bourne on it so thickest in middle articular surface
surface of articular cartilage we see
- collagen fibres anchored in underlying bone
- hoops form a corrugated surface
- springy for shock absorption and resist shear forces
synovial fluid functions and what does it contain
- contains mucopolysaccharides (hyaluronan) –> viscous fluid
- functions are nutrition of articular cartilage, lubrication and shock absorption
ligaments are
usually thickenings of stratum fibrosum in response to tensional forces
ligaments function
strengthen joints, restrain movement, aided by tendons and extrinsic ligament
ligaments made up of
almost pure collagen
difference between tendons and ligaments
ligaments are NOT associated with muscle, tendons are
some ligaments that are remnants of
tendons
true or false ; some ligaments hardly restrain movement
true
menisci
special fibrocartilage articular structures
where are menisci found
stifle and temporo-mandibular joints only
menisci function
shock absorbers, may also increase ‘fit’ or SA joint
what do menisci have which is atypical for cartilage
a nerve supply
dislocation/ luxation of joints is prevented by
- shape or articualr surfaces
- ligaments
- muscles or tendons
- cohesive force (= surface tension) of synovial fluid
flexion
reduce angle of joint
extension
increase angle of joint
overextension
extend over 180 degrees
gliding
rubbing between joints
abduction
move away from midline
adduction
move toward midline
circumduction
large circular movement of limb
bursae
- not a joint
- synovial structures
- reduce friction between tendons and bones
when synovial bursa wrap all the way around tendons they are called
tendon sheath
tendon sheaths are held in place by tissue called
retinaculum
sesamoid bones
small gliding bones associated with tendons where tendons run over synovial joints
sesamoid bone functions
reduce fiction and maintain alignment +/- increase leverage
