Joints Flashcards
what is the definition of a joint
The union between two bones, but joints do not necessarily imply movement as some are specialised to permit little or no movement
how are bones classified
based on the way in which the bones are held togetehr
what are the three groups of joints
fibrous
cartilaginous
synovial
what is a fibrous joint and what are the three types
united by collage
- sutures
- syndesmosis
- gomphosis
what is a cartilaginous joint and what are the two types
united by cartilage
- synchondroses or primary cartilaginous joints
- symphysis or secondary cartilaginous joints
what do synovial joints do
unite the skeletal elements by fibrous capsule which is fluid filled
fibrous joints : sutures
where are they found
found only between skull bones
fibrous joints : sutures
structure in the foetal skull
- sutures are wide and the bones present smooth opposing surfaces
- this allows a slight degree of movement between the skull bones during the passage of the head through the birth canal
fibrous joints : sutures
structure after birth
- sutures become quite rigid
- allowing no movement between the articulating bones
- sutures develop into one of three types
- as time goes on sutures lock together begin to ossify and fuse and disappear
fibrous joints : sutures
types of sutures after birth
squamous
serrated
denticulate
fibrous joints : syndesmosis
structure
two bony components are slightly apart, united by an interosseous membrane and a little movement is permitted between them
e.g. in between radius and ulna
fibrous joints : gomphoses
structure
has the form of a peg in socket i.e. the root of a tooth in the jaw
- fibrous tissue is arranged as the periodontal ligament
cartilaginous joints : symphyses
structure
partially moveable joint in which the apposing surfaces are covered by hyaline cartilage but separated by intervening fibrous tissue or fibrocartilage.
cartilaginous joints : symphyses
where are they found
in midline of body
e.g. sternum and vertebrae, between two halves of the pelvis
cartilaginous joints : synchondroses
where do these joints develop
between bones of endochondral origin
cartilaginous joints : synchondroses
structure
solid plate of hyaline cartilage between apposing surfaces. The cartilage plate acts as an epiphyseal plate between primary and secondary ossification centres of long bones and therefore provides an area for growth
synovial joints : four basic features
and 2 features that are sometimes present
- ends of bones are covered by hyaline cartilage
- the presence of a joint cavity
- a joint capsule
- a synovial membrane
- (disc)
- (bursae)
synovial joints : why is bone not suitable for forming apposing surfaces
- its rigidity means that the forces are transmitted over a small area of contact and thereby generating enormous pressures
synovial joints : why is cartilage a suitable surface for forming apposing surfaces
- tough, but deformable and surface adapts under pressure
- its elastic properties allow it to regain its original form when the pressure is removed
synovial joints : joint cavity
the ends of the bones are separated by a joint cavity which is not large and contains a small amount of synovial fluid
synovial joints : what is the structure of the joint capsule
- joint capsule surrounds joint like a sleeve completely enclosing it
- consists of bundles of collagen fibres
- may vary in tautness and thickness
- thickenings of capsule are called ligaments
synovial joints : where is the synovial membrane
- capsule is lined by a synovial membrane but not the articular surfaces and has a rich capillary network
synovial joints : what does the synovial membrane contain and what are its properties
- membrane capable of both secretion and absorption of fluid
- viscosity of fluid changes with the speed of joint movement becoming thinner as the speed increases
synovial joints : what are discs and where are they found
- may be interposed between articular surfaces thus dividing joint into two cavities and thereby increasing the range of movements possible at a joint
- discs may also increase the congruency of the joint and to help spread the load over the joint
synovial joints : what are bursae and where are they found
- sacs filled with synovial fluid
- most bursae are found close to the joint and may have continuous synovial membranes
- occur in places where structures which move relative to each other are in close apposition
synovial joints : how are synovial joints classified
shape of joint surfaces
or
movements which take place at the joint
types of joints
ball & socket condyloid - knuckles hinge - elbow plane ellipsoid in foot saddle - shaped - base of thumb pivot - allows head to turn
movements - what is the simplest movement
gliding - two surfaces slide past eachother
other movements occur in pairs of opposites - what are they
angular or rotationary
angular movements
flexion and extension
abduction and adduction
what is flexion
decreases angle at joint
what is extension
inc angle at joint
what is abduction
to move away from the midline
what is adduction
to move towards the midline
rotational movements
external (lateral) and internal (medial)
what is external
to turn away from midline
what is internal
to turn towards midline
special terms that apply to specific joint
pronation - to turn the palmar surface of the hand to face posteriorly
supination -to turn the palmar surface of the hand to face anteriorly
inversion - to turn plantar surface of the foot medially
eversion - to turn plantar surface of the foot laterally
what are joints that only have one axis of rotation called?
uniaxial
in smaller joints movement is possible in all directions what are they referred to as
non axial
what features is movement at synovial joint related to
- shape of articulations
- the tension of the joint capsule
- the position of ligaments
- the position of the muscle surrounding the joint
the temporomandibular joint : shape of articulation
- condyle of the mandible is roller shaped and fits into the fossa in the temporal bone
- fossa is surrounded by a bar of bone except anteriorly
the temporomandibular joint : joint capsule
has a loose capsule attached to the margins of the articular area
the temporomandibular joint : ligaments
the lateral ligament is a thickening of the joint capsule
- two accessory ligaments
the temporomandibular joint : muscles
4 major pairs of muscles which move the joint
- muscles form a rotator cuff around the joint and confer dynamic stability to the joint
what is the movement in fibrous joints
sutures - none
syndesmosis - little
gomphoses - shock absorbing
what is the movement in cartilaginous joints
synchondroses - none
symphysis - little
what is the movement in synovial joints
allow a lot of movement
