18 - Joints and Joint Tissue Flashcards
What do I need to know?
- Classification of joints and features of each
- Structure and function of the intervertebral joint and the changes that occur with ageing and damage
- Structure, function and pathology of a synovial joint
What is a joint?
The junction of 2 or more bones that allows for movement (may be small or large)
How are different joints classified?
According to the types and arrangements of the component tissues
What are the types of joints?
There are 4
- Synarthroses (fibrous joints)
- Synchrondroses (primary cartilaginous joints)
- Secondary cartilaginous joints
- Diarthroses/Synovial Joints
Describe synarthroses joints
- also called fibrous joints as the bones are united by fibrous tissue that insert into the bones (Sharpey’s Fibres)
- allows the bones to move relative to each other without moving apart
- permits little movement
What are the 2 types of synarthroses joints?
Joints that may fuse = Synostosis
Joints that don’t fuse = Syndesmosis
What is a synostosis joint?
A synarthroses/fibrous joint that may fuse for example the sutures of the skull
What is a syndesmosis joint?
A synarthroses/fibrous joint that is unfused for example the interosseous membrane
What are the 2 types of a synostosis synarthroses joint?
Squamous and serrate (interdigitate)
> occurs in the sutures of the skull
> there is LITTLE movement at these joints
What is a fracture of the epiphyseal plate called?
Salter Harris Fracture
What is a primary synchondroses joint?
- primary cartilaginous joint (bone - cartilage - bone)
- permit very small movement/immovable
What are 2 examples of a primary synchondroses joint?
- epiphyseal plate
- costal cartilages
What type of joint is the epiphyseal plate converted into?
Primary cartilaginous joint > synostosis (fused bones)
What percentage of childhood long bone fractures does a Salter-Harris Fracture make up?
15% (fracture epiphyseal plate)
> both the joint and left over line is a point of weakness
What is the significance of having synchondroses at the costal cartilages?
- need considerable flexibility for ventilation movements - calcifies and becomes stiff with age)
- between anterior ribs and sternum (posteriorly they are synovial)
Epiphyseal … eventually leaves as bone is ….
Epiphyseal lines eventually leaves as bone is remodelled
What are secondary synchondroses joints?
- bone > cartilage > FCT > cartilage > bone
- is a wider joint; has little movement but is flexible
What are 2 exmaples of a secondary synchondroses joint?
- Intervertebral disc
2. Manubrio-sternal joint
Describe the intervertebral disc as a secondary synchondroses joint
- there are collagen fibres on the outside of the disc that sweep from 1 body to the next (AF); the majority of these fibres run at angles
- there are 2 plates of hyaline cartilage (remaining from the fetal vertebral disc; the rest has ossified) with fibrous tissue (AF & NP) in between
Describe the intervertebral disc as a secondary synchondroses joint
- centre of ossification/micro-cancellous bone
- hyaline cartilage plate
- AF & NP
- hyaline cartilage
- bone …
Intervertebral Disc =
2 x plates of hyaline cartilage
(fibrocartilage)
AF
NP
What are Sharpey’s Fibres?
- collagen fibres from the AF that insert into the collagen and bone as it develops
- occurs especially at the periphery and are firmly embedded so it is hard to pull the AF away from the bone
Where do you find fibrocartilage?
At the point where the collagen fibres from the AF insert into the cartilage plates (sharpey fibres)
Are you more likely to pull off the bone or break the AF/sharpey fibres?
Break the bone
How do you identify the NP?
- lighter staining
- less dense/conc of collagen fibres
- hydrated
- loose CT