joints Flashcards
what is a joint
union between 2 or more rigid components (bone or cartilage)
also known as articulation
why do we need joints
movement and growth
what are the 3 types of joints
fibrous
cartilaginous
synovial
fibrous joints
dense fibrous connective tissue - collagen fibres hold the bones together
high tensile strength
little movement in adults
examples of fibrous joints
periodontal ligament
cranial sutures
interosseous membranes
types of cartilaginous joints
1y: synchondroses
2y: symphyses
1y cartilaginous joints
allow for bone growth
disappear in adults
no movement - movement can lead to growth plate fractures
made from hyaline cartilage
2y cartilaginous joints
don’t ossify with age
found in midline of the body
limited movement
hyaline + fibrocartilage
hyaline cartilage
pearly, translucent, fairly elastic and may ossify with age
fibrocartilage
fibrous and more resistant than hyaline cartilage
synovial joints
greatest movement
may also contain articular discs, ligaments and bursae
synovial membrane
produces synovial fluid which lubricates the joint
articular cartilage
hyaline cartilage
articular discs
firther from the centre of the body
ligaments in synovial joints
in and around the joint
can be part of the capsule or outside it
6 types of synovial joints
hinge saddle plane pivot condylar (ellipsoid) ball and socket
movement at pivot joint
rotational e.g. top of the spine
movement at plane joint
sliding and gliding
8 joint movements
flexion/extension abduction/adduction lateral/medial rotation circumduction supi-/pronation inversion/eversion dorsi-/plantarflexion true flexion/extension
flexion
two ventral surfaces closer to each other (vice versa for extension)
abduction
moving a limb away from the midline
adduction
moving a limb towards the body
lateral rotation
outwards (bending arm at elbow to 90 degrees then moving forearm away from body)
medial rotation
towards the midline
circumduction
drawing a circle in the air with whole arm/leg
combination of flexion, extension, abduction and adduction
supination
palm facing upwards
pronation
palm facing down
inversion
moving just the foot towards the midline
eversion
moving just the foot away from the midline
dorsiflexion
raising the foot upwards towards the shin
flexion
plantarflexion
moving the food back away from the shin
joint stability
- The more degrees of freedom, the less stable the joint/higher risk if dislocation
- Shape of articulating surfaces (e.g. shoulder vs hip, hip is very deep socket and much more stable than the shoulder joint which is easier to dislocate)
- Fibrous capsule and ligaments (surround the joint, hold everything in place)
Muscles (strong, support the joint), special group of muscles in the shoulder joint which act to support the joint and stabilise it
blood supply to the joints
rich blood supply
anastomoses (communication between 2 blood vessels w/o an intervening capillary network) - lots of blood vessel branches that reconnect, allows blood an alternative path e.g. during extreme flexion and extension
nerve supply to the joints
rich nerve supply
- Proprioception (specialised sensory nerve endings that monitor internal changes in the body brought about by movement and muscular activity) - allows sense of the relative position of different parts of the body
○ Proprioceptors not just in muscle spindles but also in joint capsules
Hilton’s law: the nerve supplying a muscle that crosses a certain joint, also innervates this joint
trauma to the joint
(fracture at the joint of the bone, dislocation), close to the joint there is only a thin layer or compact bone (mainly spongy bone)
arthritis
(osteo- and rheumatoid) - osteo is the degenerative joint disease, not as simple as wear and tear. Rheumatoid is an autoimmune disease and can also affect other parts of the body.
craniosynostosis
(abnormal skill growth due to premature fusion of cranial structures)
Sutures in the skull close too early, causes problems in childhood as the brain is still growing and the skull is no longer flexible, leads to deformed skull and can lead to impairments (e.g. can compress nerves)
