Joint Flashcards
What are the function of joints
Allow movement in 3-dimensions
Bear weight
Transfer the load evenly to the musculoskeletal system
What are the structural classifications of joints
Fibrous
Cartilaginous
Synovial
What is an example of a fibrous joint
Teeth sockets
What is an example of cartilaginous joints
Intervertebral discs
What is an example of synovial joints
Metacarpophalangeal
What are the functional classifications of joints
Synarthroses
Amphiarthroses
Diarthroses
Define synarthroses with example
Immovable joints, mostly fibrous
e.g. skull sutures
Define amphiarthroses with example
Slight moveable joints, mostly cartilaginous
E.g. intervertebral discs
Define diarthroses with examples
Freely moveable joints, mostly synovial
E.g. hip
What are the three examples of fibrous joints
Sutures
Syndesmoses
Gomphoses
Explain sutures
Occur only between bones of the skull - allow skull growth in development
Adjacent bones interdigitate
Junction filled with very short tissue fibres
Describe syndesmoses
Bones are connected by a cord (ligament) or sheet (interosseous membrane) of fibrous tissue
Amount of movement permitted is proportional to length of fibre
Describe gomphoses
A peg-in-socket fibrous joint found only in tooth articulation
Examples of cartilaginous joints
Synchondroses
Symphyses
Describe synchondroses
Bones are directly connected by hyaline cartilage
Usually amphiarthroses e.g. slightly moveable e.g. costal cartilage of the rib
Describe symphyses
Connecting cartilage is a pad or a plate of fibrocartilage e.g. intervertebral discs
Joint classification summary
Fibrous - synarthrosis - suture, syndesmosis, gomphosis
Cartilaginous - amphiarthrosis - synchondrosis, symphysis
Synovial - diarthrosis
Describe synovial joints
Articulating bones are separated by fluid-filled cavity
Most joints in the body fit into this category
What are the 5 characteristic features of synovial joints
Articular cartilage
Joint capsule - the inner layer is the synovial membrane
Joint (synovial) cavity - a space filled with synovial fluid
Synovial fluid
Reinforcing ligaments
What are the types of cartilage
Elastic cartilage
Fibrocartilage
Hyaline cartilage
- all contain chondrocytes - synthesise extracellular matrix
Define bursae
Fluid filled sacs lined by synovial membrane
Define menisci
Disc of fibrocartilage
2 cover surface of tibia and femur
Describe articular (hyaline) cartilage
Almost frictionless surface
Resists compressive loads
High water content
Low cell content
No blood supply
What are the articular cartilage zones
Superficial zone (10-20%)
Middle/intermediate zone (40-60%
Deep zone (30%)
Calcified zone
Subchondral zone
Describe synovial fluid
Joint lubricant
Covers articulating surfaces with thin film (0.5ml)
Modified from plasma by synovial membrane (synoviocytes)
Result = slimy fluid - like egg white
Reduce friction during articulation
Describe synovial membrane
Sits on the joint capsule and encloses synovial cavity
Only a few cells thick
Can have villi and projections to increase surface area
Secretes synovial fluid components - hyaluronate and a source of inflammatory cells in rheumatoid arthritis
What do ligaments connect
Bone to Bone
What is the role of ligaments
Stabilise joints
Less regularly arranged fibre than tendons
Can stretch up to 6% before breaking
May contain more elastic fibres than tendons (generalisation)
What do tendons connect
Bone to muscle
What is the role of tendons
Stabilise joints
Made of dense regular connective tissue - rich in type 1 collagen
Allow muscles to be accommodated at a distance from their insertion
Provides a solid base (insertion to bone) on which muscles can pull
What stabilises joints
Ligaments
Tendons
Muscles
How do joint mechanics work
A synovial joint is the fulcrum of a level system
A lever can apply a torque (twist) about a fulcrum, proportional to force x distance
Describe a first class lever
Fulcrum is in the middle (elbow joint)
The force is at one end (the triceps muscle)
Resistance is at the other end (the weight being pulled) e.g. pulling weight downwards
Describe a second class level
The fulcrum is at one end (e.g. temporomandibular joint)
The force is at the other end (the muscles of the chin)
Resistance is at the centre (the muscles attached to the coronoid process)
Describe third class lever
Fulcrum is at one end (e.g. elbow joint)
The force is in the middle (biceps muscle)
Resistance is at the other end (the weight being pulled) e.g. pulling the weight upwards
What type of joint is the hip joint
Synovial joint - ball and socket
Held in securely in place by strong ligaments and heavy cylindrical joint capsule
What are the main stabilising ligaments in the hip joint
Iliofemoral
Pubofemoral
Ischiofemoral
Describe the shoulder joint
Ball and socket
Stability sacrificed for rang of movement
Joint capsule is loose
Dislocation of the shoulder quite common
Rotator cuff muscles help in stabilisation but are prone to injury - especially at tendon insertion sites
What are the stabilising ligaments of the shoulder
Glenoidal labrum - fibrocartilage
Coracohumeral ligament
Three glenohumeral ligaments
Transverse humeral ligament
What are the tendons and muscles which stabilise the shoulder
Long head of biceps branchii
Tendons of the rotator cuff
- subscapularis
- suprascapularis
- infraspinatus
- teres minor
What is the knee joint
Not a hinge joint
Femur and tibia = condyloid - ovoid head of one bone moves in an elliptical cavity of another
Femur and patella = gliding
Joint capsule thin but strengthened by many tendons and ligaments
