Joints Flashcards
Functions joints allow:
- permit limited movement
- transfer forces from one bone to another
What are the joint classifications? And how are they united?
- fibrous (allow little to no movement, united by fibrous tissue)
- cartilaginous (allows limited movement, united by hyaline or fibrocartilage)
- synovial (allows movement, united by a synovial joint capsule)
Joints can be classified by range of motion possible - what are they?
- synarthrosis (no movement)
- Amphiarthrosis (limited mobility)
- Diarthrosis (free movement)
Describe the synovial joint
- majority of joints
- bones separated by fluid-filled space, lined with hyaline cartilage (low friction and allows the most movement of all joint types)
- articulating surfaces and joint enclosed by joint capsule
- inner synovial membrane
- strengthened by outer fibrous layer
What does the synovial membrane do?
- contains synovial lining cells which produce hyaluronic acid for viscosity
- produced synovial fluid
- inner synovial membrane strengthened by outer fibrous layer
- contains simple squamous epithelium
- contains blood vessels and lymph (fenestrated capillaries, reabsorb and renewal of fluid)
What does articular or hyaline cartilage do?
- reduces friction and acts as a shock absorber
What does the joint capsule do?
- contains synovial fluid
- an envelop around the joint
What does synovial fluid do?
- provides cushioning
- takes nutrients to the site and waste away from the site
- lubricates the joint and reduces friction
- maintains articular contact
Describe articular hyaline cartilage
- no blood vessels or nerves
- withstand loads of pressure without pain or bleeding
- slow/limited healing and repair
- good at resisting compression
- smooth surface, low friction
Describe the connective tissue in joints
- few cells, chondrocytes 1-3%
- extracellular matrix
- hydrophilic proteoglycans (e.g., hyaluronic acid)
- water 70-80%
- collagen fibres (type 2)
Describe ligaments within a joint?
- strong white/fibrous ligaments hold together bones
- restrict movement (along with the shape of articular surfaces)
- intra vs extra capsular
Describe intracapsular ligaments
- within joint capsule
- not within joint space
- synovium reflects over them
Describe menisci or semilunar cartilages
- found in some synovial joints (stifle, teres major)
- crescent shaped fibrocartilages
. load distribution
. shock absorption
. stabilisation
What protects tendons near joints?
- sesamoids ~ ossification or chondrification
- tendon sheaths and bursae ~ sacs/tubes containing cavities filled with synovial fluid and with synovial lining
Describe how a joint gets it nervous and vascular supply
- blood vessel to epiphysis and joint capsule (not cartilage)
- free sensory fibres (pain) from joint capsule/synovium
- motor fibres to blood vessels
- sensory fibres from blood vessels
- proprioceptive fibres from joint capsule
What are the 6 degrees of freedom?
- cranial-caudal translation
- proximal-distal translation
- medial-lateral translation
- rotate around the craniocaudal axis
- rotate around the proximodistal axis
- rotate around the mediolateral axis
what does rotating around the mediolateral axis result in?
- flexion = bending
- extension = straightening
What does rotation around craniocaudal axis result in?
- adduction = bringing back towards the midline of the body
- abduction = taking away from the midline from the body
rotation around the proximodistal axis will result in what?
- pronation (internal rotation) = lateral surface rotated inwards
- supination (external rotation) = medial surface rotated outwards
Movement types are often what?
- coupled
- biological joints don’t strictly do pure movements in just one degree of freedom
The mobility of a joint depends on what?
- the shape of the bones
- the ligaments connecting them
What are the types of synovial joints
- plane (prince)
- hinge (harry)
- pivot (pulled)
- condylar (charles)
- ellipsoid
- saddle
- ball-and-socket (bag)
Describe a plane joint
- two flat surfaces
- translation, no real rotational movements
- articular process of equine cervical vertebrae
Describe the hinge joint
- cylindrical surface and corresponding receiving surface
- usually a notch to limit sideways motion
- movement (rotation) in one plane only
- e.g., equine metacarpophalangeal joint
Describe the pivot joint
- peg fitted withing ring
- rotational movements of peg within ring
- bovine atlantoaxial joint
Describe the condylar joint
- two knuckled-shaped condyles with with corresponding concave surfaces
- mostly rotation about transverse axis running between condyles, but rotation about other axes and translation also possible
Describe a ellipsoidal joint
- ovoid convex surface with corresponding concavity
- rotation and translation in two planes
Describe the saddle joint
- two fitting surfaces, each maximally convex in one direction and maximally concave in another
- rotation and translation dictated by geometry of surfaces
Describe a ball and socket joint
- sphere and cup morphology
- up to six degrees of freedom
