Joints pt 1 Flashcards
Articulations
site where 2/more bones meet
Functions: gives skeleton mobility, hold skeleton together
classifications: functional + structural
Functional classification of joints
Based on amount of movement joint allows
3 functional:
1. synarthroses: immovable joints (syn = together, arthro = joint)
2. amphiarthroses: slightly movable joints
3. Diarthroses: freely movable joints
Structural classification of joints
Based on material binding bones together and presence/absence of joint cavity
3 structural:
1. fibrous joints
2. cartilaginous joints
3. synovial joints
Fibrous joints
- bones joined by dense fibrous CT
- no joint cavity
- most synarthrotic (immovable) depends on length of CT fibers
- 3 types:
1. Sutures: joint held by short interconnecting fibers. (skull)
2. syndesmoses: held by ligament and fibrous tissue longer than sutures
3. gomphosis: peg in socket, periodontal ligament holds tooth in socket, fibrous joint
Cartilaginous joints
- bones united by cartilage
- no joint cavity
- not highly movable
- 2 types
1. synchondroses: immovable, united by hyaline cartilage
2. symphyses: slightly movable, united by fibrocartilage
Synovial joints
- bones separated by fluid filled joint cavity
- all are diarthrotic
- include all limb joints, most joints of body
non distinguishing features:
- fatty pads: for cushioning bw fibrous layer and synovial membrane/bone
- articular discs (menisci): fibrocartilage separates articular surfaces to improve fit of bone ends, stabilize joints, and reduce wear and tear
structures:
1. bursae: sacs lined with synovial membrane (contain synovial fluid)
- reduce friction where ligaments, muscles, skin, tendons, or bone rub
- tendon sheaths: elongated bursa wrapped completely around tendon subjected to friction
6 distinguishing features in synovial joints
- Articular cartilage: hyaline cartilage
- prevents crushing of bone ends - Join (synovial) cavity: small fluid-filled potential space
- Articular (joint) capsule
- 2 layers: external fibrous layer (dense CT) and inner synovial membrane (loose CT, makes synovial fluid) - Synovial fluid
- viscious, slippery filtrate of plasma and hyaluronic acid
- lubricates and nourishes articular cartilage
- contains phagocytic cells to remove microbes and debris - different types of reinforcing ligaments
- capsular: thickened part of fibrous layers
- extracapsular: outside capsule
- intracapsular: deep to capsule; covered by synovial membrane - Nerves + blood vessels
- nerve fibers detect pain, monitor joint position (proprioception) and stretch
- capillary beds supply filtrate for synovial fluid
3 stabilizing factors of synovial joints
- shapes of articular surfaces (minor role)
- ligament number and location (limited role)
- muscle tendons that cross joints (most important)
- muscle tone keeps tendons taut, extremely important in reinforcing shoulder + knee joints and arches of the foot
Movement allowed in synovial joints
- all muscles attach to bone/CT at no fewer than 2 points (origin: attachment to immovable bone, insertion: attachment to movable bone)
- muscle contraction causes insertion to move toward origin
- movements occur along transverse, front, sagittal planes
Range of motion for synovial joints
- nonaxial: slipping
- uniaxial: movement in one plane
- biaxial: movement in 2 planes
- multiaxial: movement in/around all 3 planes
3 general movements of synovial
- Gliding: one flat bone surface glides/slips over another similar surface
- flat bones surface moves side to side
- no alteration of joint angle
- limited range due to articular capsule + ligaments
- intercarpal joints (wrist bones)
-intertarsal joints (ankle bones)
- bw articular processes of vertebrae - Angular movements: increase/decrease angle bw 2 bones
- flexion (decrease angle of joint)
- extension (increase angle of joint)
- hyperextension (excessive extension beyond normal ROM)
-abduction: movement away from midline
- adduction: movement toward midline
- circumduction: involves flexion, abduction, extension, and adduction of limb (limb describes cone in space, circular) - rotation: turning of bone around its own long axis
- toward midline/away from it
- medial and lateral rotation
- ex: bw C1 + C2 vertebrae, rotation of humerus + femur
Special movements at synovial joints
- supination + pronation of radius + ulna
- dorsiflexion + plantar flexion of foot
- inversion + eversion of foot
- protraction + retraction of scapula
- elevation + depression of mandible
- opposition of thumb
