Anatomy Chp 8

joints

also called articulations; places where two or more bones meet

joint structure

determines function and range of motion

trade-off of joints

mobility vs. stability- more movement = less stability (high injury risk)

classification methods of joints

1. by range of motion (functional)

2. by structure (histological)

functional classification terms

synarthrosis, amphiarthrosis, diarthrosis

synarthrosis

immovable

amphiarthrosis

slightly moveable

diarthrosis

freely moveable (synovial joints)

synarthroses

• bones held by dense connective tissue

• little or no movement

• function: strength, protection, force distribution

• examples:

  • suture → skull bones

  • gomphosis → tooth in socket

  • synchondrosis → epiphyseal plate

  • synostosis → fused bones

amphiarthroses

• bones connected by cartilage or ligaments

• limited movement

• examples

  • syndesmosis → ligament connects bones

  • symphysis → fibrous cartilage pad

diarthroses

always have:

• joint capsule

• articular cartilage

• joint cavity

• synovial membrane

• accessory structures

• sensory nerves

• blood vessels

• synovial fluid functions:

  • lubrication

  • nutrient delivery

  • shock absorption

accessory structures

• menisci

• fat pads

• ligaments

• tendons

• bursae

menisci

fibrous cartilage pads

fat pads

cushioning, space-filling

ligaments

capsular, extracapsular, intracapsular

tendons

stabilize joint via muscle tone

bursae

fluid filled sacs that reduce friction

• tendon sheaths = elongated ____

synarthrosis

strongest joint

diarthrosis

weakest joint

increases stability

ligaments, joint shape, muscle tone

axes of motion

• superior-inferior

• medial-lateral

• anterior-posterior

types of movement

angular motion, rotation, special movements

angular motion

• flexion → decreases joint angle

• extension → increases joint angle

• hyperextension → beyond normal (injury risk)

• abduction → away from midline

• adduction → towards midline

• circumduction → circular motion

rotation

• medial (internal)

• lateral (external)

• pronation → palm faces posterior

• supination → palm faces anterior

special movements

• inversion/eversion (foot)

• dorsiflexion/plantar flexion (foot)

• lateral flexion (spine)

• protraction/retraction (jaw/shoulders)

• opposition/reposition (thumb)

temporomadibular joint (TMJ)

• synovial hinge + gliding joint

• fibrous cartilage (not hyaline)

• articular disc divides joint into two cavities

• high mobility, high dislocation risk

• movements;

  • elevation

  • depression

  • protraction

  • retraction

  • side-to-side

intervertebral joints

1. intervertebral disc (symphysis)

2. two zygapophysial (facet) joints (synovial)

intervertebral disc structure

• anulus fibrous → outer fibrous cartilage

• nucleus pulposus → inner gelatinous core (shock absorber)

• endplates → attach disc to vertebrae

aging effects of intervertebral joints

low water content, decreases height, high herniation risk

shoulder complex

• only one attachment to axial skeleton → huge mobility

• mobility > stability

• stability mainly from muscles → rotator cuff

sternoclavicular joint

• “master joint”

• positions scapula

• has articular disc

glenohumeral (shoulder) joint

• ball-and-socket

• shallow socket → easily dislocated

• glenoid labrum deepens socket

elbow joint

• hinge joint

• actually 3 joints in one capsule

• very stable due to:

  • bone shape

  • thick capsule

  • strong ligaments

radio-ulnar joints

• allow pronation and supination

• linked by interosseous membrane

wrist joint

• radiocarpal joint → condylar

• intercarpal joints → plane

• doesn’t position hand much but affects tendon efficiency

hand joints

• thumb carpometacarpal joint → saddle (opposition)

• MCP joints → condylar

• interphalangeal joints → hinge

hip joint

• strongest synovial joint

• ball-and-socket

• acetabular labrum deepens socket

• extremely stable → fractures more common than dislocations

knee joint

• most complex hinge joint

• two joints → tibiofemoral, patellofemoral

• menisci crucial for stability

• major ligaments → ACL/PCL, MCL/LCL

• locking mechanism stabilizes knee in extension

ankle joint (talocrural joint)

• hinge joint

• dorsiflexion and plantar flexion

• stability from ligaments and malleoli

foot joint

• designed for support and flexibility

• intertarsal, tarsometatarsal, MTP joints

aging joints

• low cartilage

• low synovial fluid

• high stiffness and fracture risk

• arthritis= inflammation of synovial joints

• exercise helps slow degradation

joints

• where two bones meet

• fluid, cartilage, or fibrous tissue

• tradeoff of flexibility and strength

synarthosis

no movement

types: fibrous, cartilaginous, bony fusion

fibrous synarthrosis

suture (sutural ligaments), gomphosis (periodontal ligaments)

cartilaginouse synarthoris

synchondrosis (ex: btwn ribs and sternum)

bony fusion synarthrosis

synostosis (ex: fusion of frontal bones)

amphiarthrosis

some movement

types: fibrous, cartilaginous

fibrous amphiarthrosis

syndesmosis

• between tibia and fibula

• between fibula and talus

cartilaginous amphiarthrosis

symphysis

• pubic symphysis

• intervertebral discs

diarthrosis (synovial)

free movment

key parts of diarthrosis

• fibrous joint capsule

• synovial membrane

• articular cartilages

• joint cavity containing synovial fluid

synovial fluid

• lubricates articular cartilages and reduces friction

• nourishes chondrocytes of articular cartilages

• acts as shock absorber

accessory structures of a knee joint

• bursa

• fat pad

• meniscus

• tendons

• blood vessels

• nerves

• ligaments

  • extracapsular

  • intracapsular

pivot joint

ex: btwn C1 and C2

hinge joint

ex: elbow

saddle joint

ex: btwn trapezium carpal bone and 1st metacarpal bone

ball and socket joint

ex: hip joint

condyloid joint

ex: btwn radius and carpal bones of wrist

plane joint

ex: btwn tarsal joints

abduction

away from longitudinal axis

• frontal plane; lateral/medial

adduction

towards longitudinal axis

• frontal plane; lateral/medial

flexion

decreases angle btwn bones; bend forward

• anterior/posterior plane

extension

increases angle btwn bones'; bend backwards

• anterior/posterior plane

hyperextension/flexion

movement beyond normal limits

types of angular motion

• adduction/abduction

• flexion/extension

• rotation

• supination/pronation (up/down)

• eversion/inversion (moving feet lateral/medial)

• dorsiflexion/plantar flexion (moving feet up/down)

• posterior/anterior (ex: jaw)

• inferior/superior (ex: jaw)

• opposition/reposition

TMJ (temporomandibular joint)

• 2 synovial cavities in same place

• very loose

• allows for chewing

• plane and hinge joint

intervertebral ligaments

• ligamentum flavum

• posterior longitudinal ligament

• interspinous ligament

• supraspinous ligament

• anterior longitudinal ligament

intervertebral disc

• vertebral endplate

• anulus fibrosis

• nucleus pulposus

zygapophysial joints

articular processes between vertebrae

herniated/bulging discs

damages anulus fibrosis causes herniation of nucleus pulposus

sternoclavicular joint

only joint for axial and upper appendicular

• two synovial cavities

• two plane joints

glenohumeral joint

• ball and socket

• greatest range of motion (high injury risk)

• triaxial

elbow joint

3 joints within one capsule

• 2 hinge joints: humero-ulnar (strongest; trochlea and trochlear notch) and humeroradial (more flexible; capitulum and head of radius)

• 1 pivot joint: proximal radio-ulnar

proximal and distal radio-ulnar joints

pivot joints, allow rotation

proximal radio-ulnar joint

head of radius and radial notch of ulna

distal radio-ulnar joint

ulnar notch of radius and head of ulna

radio-ulnar ligament and interosseous membrane

stabilize distal joint, allows for supination/pronation

condylar joints

• flexion/extension

• adduction/abduction

• circumduction

wrist joint

radiocarpal joint anf intercarpal joint

femur joint

ball and socket joint

• fat pad absorbs shock

knee joint

• works as hinge joint

• ligaments, menisci, tendons, bursa and fat pad all stabilize joint

• ligaments prevent hyperextension/flexion and allow for extensive adduction/abduction

• cruciate ligaments allow locking/unlocking of joint and allow you to stand for long periods of time

ligaments that stabilize knee joint

• anterior/posterior cruciate ligament

• tibial/fibular collateral ligament

• popliteal ligament

talocrural joint

hinge joint; talus, tibia, fibula)

• limited dorsiflexion

• limited plantar flexion

tibiotalar joint

hinge; main joint; bears body mass; supported by:

• proximal tibiofibular joint: plane joint

• distal tibiofibular joint: fibrous syndesmosis

• fibulotalar joint: fibrous syndesmosis