Anatomy of joints Flashcards
What is a joint?
It is the site of the meeting of 2 or more bones together
How are joints classified?
- Based on the connecting structure between the articular surface, the “surface where two bones meet”, & the degree of mobility and movement allowed at the joint
What are the different types of joints?
1) Fibrous joint
2) Cartilaginous joint
3) Synovial joint
Describe a fibrous joint.
- Articular surfaces are connected by a strong fibrous tissue
- No movement is permitted
- Found in:
a) Sutures of the skull “ossified with age AKA turns into bones”
b) Inferior tibiofibular J. (Syndesmosis) AKA between the Tibia and Fibula
c) Between the teeth and joints (gomphosis)
Describe a cartilaginous joint
- Bones that are connected together by cartilage
- Divided into primary and secondary:
1) Primary (hyaline cartilage):
- Bones are connected by hyaline cartilage
- No movement
- Ossifies with age
- Found in (Epiphyseal cartilages “between head and shaft of long bones”, & between the 1st costal cartilage and sternum “AKA manubrium”)
2) Secondary (fibrocartilage sandwiched between hyaline cartilage):
- Bones are connected by a disc of dense white fibrocartilage “firm but flexible”
- Limited movement
- Ossifies rarely
- Found in the midline of the body (Intervertebral discs “might ossify normally or pathologically”, symphysis pubis, joints between species of the sternum)
What is a nucleus pulposes?
The central gel-like core of the intervertebral disc which functions as a shock absorber, is surrounded by an annulus fibrosis providing it with strength and stability to the intervertebral discs
How does disc prolapse/herniation occur?
When the annulus fibrosus weakens or tears, the nucleus pulposus may protrude through the outer ring.
The compressed form is when we stand up, the extended form is when we sleep, that’s why you are taller when you wake up than at late night
Describe a synovial joint
- Freely mobile joint
- Do not ossify easily, only if there is a pathology but doesn’t ossify normally
- Most common type of joint
What is the structure of a synovial joint?
- Hyaline cartilage covers the articular surfaces of bones
- The whole joint cavity is covered by a capsule (fibrous tissue), Which is thickened in certain parts forming capsular ligaments (inflexible fibrous bands)
- Outside the capsule, there are extracapsular ligaments that can be (fibrous or elastic)
- The inside of the capsule is lined with synovial fluid
- It might contain intra-articular structures like (discs, meniscus, labrum & tendons)
How are bones kept together and close to each other without touching?
By the fact of negative pressure created by the synovial joint
What is a ligament?
A cord/band of connective tissue uniting two structures that are commonly associated with joints there are two types:
a) Fibrous (unstrechable)
b) Elastic (strechable)
What is a bursa?
A lubricating device consisting of a closed fibrous sac filled with a film of viscous fluid commonly located around joint
- Found in areas where tendons rub against bones, ligaments, or other tendons
- Bursa’s cavity can communicate with the cavity of synovial joints (communicating bursa) found in the knee and shoulder joints, like the subacromial bursa found in the shoulder joint
Where do we find the olecranon bursa?
Around the elbow joint
Where do we find the tendo-calcaneal bursa?
Around the ankle
What are the different synovial joint classifications?
A) According to the shape of the articular surfaces:
1) Plane (Acromioclavicular joint)
2) Hinge (Elbow, ankle & interphalangeal joints)
3) Pivot (Atlanto-axial & radio-ulnar joint)
4) Ellipsoid (Wrist joint & metacarpophalangeal “Doesn’t allow rotation”)
5) Saddle (Carpometacarpal joint of the thumb “limited rotation”)
6) Ball & socket (Hip & shoulder joints “allows the widest range of motion”)
7) Condyloid (Knee joint, and jaw mandible)
B) According to the axes around which the movement occurs:
1) Uniaxial joint (move around one axis like the hinge and pivot joints)
2) Biaxial Joint (movement around 2 axes like the condylar & ellipsoid joints “flexion, extension, adduction, abduction”)
3) Multi-axial joint (all types of movement are allowed like the ball & socket & saddle hinge “flexion, extension, adduction, abduction, rotation”)
- plane joint can be considered as mult-axial or uniaxial in some books
C) According to the number of articulating bones:
1) Simple joint (joint formed by two bones like the acromioclavicular joint)
2) Compound joint (joint formed of more than 2 bones like the elbow)
3) Complex joint (joints comtaing intracapsular structures like the knee joint)
