JOINT

 JOINT

DEFINITION:

• Joint is a junction between 2 or more bones /cartilages.
• With expection of the hyoid bone every bone in the body is connected to form a joint.
• 23 joints in a body

FUNCTIONS:

• Holds the bone together 
• Allows the skeleton some flexibility so that gross movement can occur
• Makes bone growth possible.

CLASSIFICATION OF JOINT

1. Structural classification
2. Functional classification
3. Regional classification
4. Classification according to no.of articulating bone.

STRUCTURAL CLASSIFICATION

• Fibrous joint 
• Cartilaginous joint
• Synovial joint

  a. Fibrous joint 

• Suture 
• Syndesmosis
• Gomphosis

  b. Cartilaginous joint

• Primary cartilaginous or synchondrosis
• Secondary cartilaginous or symphysis

  c. Synovial joint ( according to shape of articulating surface )

• Ball and surface
• Saddle
• Condylar
• Hellipsoid
• Hinge
• Pivot
• Plane

FUNCTIONAL CLASSIFICATION

• Synarthrosis immovable
• Amphiarthosis ( slightly movable )
• Diathrosis ( freely movable )

REGIONAL CLASSIFICATION

• Skull type
• Vertebral type
• Limb type

FIBROUS TISSUES

• The bones are joined by fibrous tissues
• There is no joint cavity
• Most are immovable

3 types

• Suture
• Syndesmosis
• Gomphoses

TYPES OF SUTURE 

1. PLANE 
• Eg: internasal suture

   2.  SERRATE

• Eg: inter parietal suture

1. SQUAMOUS
• Eg: temporoparietal suture
2. DENTICULATE
• Eg: lambdoid suture
3. SCHINDYLESIS
• Eg: joint between rostrum of sphenoid and upper border or vomer

SYNDERMOSIS

• Bones are connected by an interosseus membrane.
• Slightly movable .
• Eg: between tibia and fibula and unlar and radius.

GOMPHOSIS

• The peg in socket fibrous joint between a tooth and its alveolar socket .

CARTILAGINOUS :

1. Primary cartilaginous joint 

• Bones are united by a plate of hyaline cartilage so that joint is immovable and strong.
• Eg: joint between epiphysis and diaphysis.

1. Secondary cartilaginous joint

• Also know as symphysis
• It is a fibres types of tissue , where hyaline cartilage ends of a bone.

SYNOVIAL JOINT 

characteristic features.

• Articular cartilage
• Synovial cavity ( joint cavity )
• Articular capsule 
• Synovial membrane  / fluid
• Reinforcing ligament 
• Fatty pads or articular disc.
• Tendon sheath 
• Bursa

GENERAL STRUCTURE OF SYNOVIAL JOINT.

1. Articular cartilage

• Hyaline cartilage
• Avascular , non -nervous and elastic
• Spongy cushions absorb compression
• Protects ends of bones from being crushed .

1. Joint (synovial)cavity

• Potential space 
• Small amount of synovial fluid 

1. Articular capsule 

• 2 layered
• Outer :fibrous capsule of dense irregular connective tissue

1. Synovial fluid 

• Filtrate of blood
• Continuous special glycoproteins
• Nourishes cartilage and function as slippery

BURSAE AND TENDON SHEATH's

• Contains synovial fluid
• Not joints but often associated with them.

Lubrication of a synovial joint

• synovial fluid 
• Hyaline cartilage
• Intra articular fibrocartilages 
• Fat pads
• Bursae

NERVE SUPPLY OF JOINTS

Hiltons law

• The nerve which supply a joint 
• Also supply group of muscles regulating the movements of muscles acting on the joint and skin over the joint.