Articular System and Joints

Question 1

What is Cartilage and what are the types of cartilage?

Answer 1

Resilient, semi-rigid connective tissue located in parts of skeleton where MORE FLEXIBILITY = required
(eg: costal cartilage of ribcage allows it to expand)

• nourished via diffusion –> very slow to repair/regrow
• articular cartilage provides smooth surfaces for joints

Types:

1. Hyaline: most common, covers bony, articular structures
   - model for early foetal skeleton
   - moderate collagen amount
2. Elastic: flexible and forms discrete structures (eg: pinna)
   - contains bundles of elastic fibres
3. Fibrocartilage: forms specialised joints and contributes to articular surfaces (eg: discs, meniscus)
   - mix of fibrous and hyaline
   - can withstand prolonged pressure
   - LOTS of COLLAGEN

Question 2

Synovial Joints

Answer 2

Moveable
- bones united by a fluid-filled joint cavity

MAJOR FEATURES:
1. Articular Hyaline Cartilage
2. Joint cavity (containing synovial fluid)
3. Ligament 
Joint capsule made up of:
4. Fibrous layer enclosing the synovial joint
- dense connective tissue (collagen)
- can thicken to form ligament 
5. Synovial Membrane:
- highly vascular
- produces fluid
- lines internal surface

ACCESSORY STRUCTRUES:

1. Discs and Meniscus:
   - made of fibrocartilage
   - extend inward from articular capsule and partially or completely divide it
   - allows separate movements on each side to occur simultaneously
   - helps to absorb compression forces
2. Labrum:
   - fibrocartilage lip that extends from edge of socket to deepen it and increase contact area b/w bones
3. Fat pads:
   - space fillers that help spread synovial fluid
   - intracapsular, but extrasynovial
4. Bursae and Tendon Sheaths:
   - bags of lube that reduce friction
   - flattened fibrous sacs lines with synovial fluid
   - very numerous in high mobility joints (eg: shoulder)

Question 3

Types of Synovial Joints

Answer 3

1. Plane Joint - sliding/gliding on flat surface (eg: b/w carpals)
2. Hinge Joint - movement at right angle to joint –> flexion/extension (eg: b/w humerus and ulna)
3. Pivot Joint: longitudinal axis of bones –> rotation
4. Condylar Joint: flexion, extension, adduction abduction –> movement around 2 axes at right angles (eg: knuckles)
5. Saddle: same as condylar, but saddle shaped bones
6. Ball and Socket: multiple axis –> flex/extension, add/abd, circumduction, rotation

Question 4

Fibrous Joints:

Answer 4

Bones united by a fibrous tissue; degree of movement depends on length of fibres

• no joint cavity: bones held tog. by dense irregular connective tissue

3 types:

1. Sutures: thin layer of connective tissue called suteral ligament (only in skull)
2. Syndesmosis: when 2 adjacent bones are linked by a ligament
3. Gomphosis: short collagen fibres running b/w root of tooth and bony socket

Question 5

Cartilaginous Joints

Answer 5

no joint cavity

1. Synchondroses: a bar of hyaline cartilage b/w 2 ossification centres of a developing bone
2. Symphysis - fibrocartilage that connects 2 separate bones (eg: invertebral discs)

Question 6

Factors Stabilising Synovial Joints

Answer 6

1. better fit = less movement
2. Additional ligaments = more stable
3. Increased strength and tightness = more stable
4. Stronger muscles wrapped around joint = more stable

INCREASED STABILITY = DECREASED RANGE OF MOVEMENT