Joints pt 1

Question 1

Articulations

Answer 1

site where 2/more bones meet

Functions: gives skeleton mobility, hold skeleton together

classifications: functional + structural

Question 2

Functional classification of joints

Answer 2

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

Question 3

Structural classification of joints

Answer 3

Based on material binding bones together and presence/absence of joint cavity

3 structural:
1. fibrous joints
2. cartilaginous joints
3. synovial joints

Question 4

Fibrous joints

Answer 4

• 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

Question 5

Cartilaginous joints

Answer 5

• 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

Question 6

Synovial joints

Answer 6

• 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

2. tendon sheaths: elongated bursa wrapped completely around tendon subjected to friction

Question 7

6 distinguishing features in synovial joints

Answer 7

1. Articular cartilage: hyaline cartilage
   - prevents crushing of bone ends
2. Join (synovial) cavity: small fluid-filled potential space
3. Articular (joint) capsule
   - 2 layers: external fibrous layer (dense CT) and inner synovial membrane (loose CT, makes synovial fluid)
4. Synovial fluid
   - viscious, slippery filtrate of plasma and hyaluronic acid
   - lubricates and nourishes articular cartilage
   - contains phagocytic cells to remove microbes and debris
5. different types of reinforcing ligaments
   - capsular: thickened part of fibrous layers
   - extracapsular: outside capsule
   - intracapsular: deep to capsule; covered by synovial membrane
6. Nerves + blood vessels
   - nerve fibers detect pain, monitor joint position (proprioception) and stretch
   - capillary beds supply filtrate for synovial fluid

Question 8

3 stabilizing factors of synovial joints

Answer 8

1. shapes of articular surfaces (minor role)
2. ligament number and location (limited role)
3. muscle tendons that cross joints (most important)
   - muscle tone keeps tendons taut, extremely important in reinforcing shoulder + knee joints and arches of the foot

Question 9

Movement allowed in synovial joints

Answer 9

• 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

Question 10

Range of motion for synovial joints

Answer 10

• nonaxial: slipping
• uniaxial: movement in one plane
• biaxial: movement in 2 planes
• multiaxial: movement in/around all 3 planes

Question 11

3 general movements of synovial

Answer 11

1. 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
2. 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)
3. 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

Question 12

Special movements at synovial joints

Answer 12

• 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