KAAP 309: Joints

Functional classifications of joints

synarthroses, amphiarthroses, diarthroses

synarthroses

immovable

amphiarthroses

slightly moveable

diarthroses

freely moveable

structural classifications of bones

fibrous, cartilaginous, synovial

fibrous (tissue? joint cavity? movable?)

dense CT, no joint cavity, immovable

Fibrous types

sutures, gomphoses, syndesmoses

Sutures

only in the skull; will ossify during middle age; immobility is key to protection of the brain

gomphoses

located in the tooth and socket; allows microscopic movement with pressure

syndesmoses

bones connected by ligaments and fibrous tissues; movement is based on the length of the connecting fibers

Cartilaginous joints (tissue? joint cavity? movable?)

connected through cartilage disc, no joint cavity; minimal movement

cartilaginous joints types

synchondroses and symphyses

synchondroses

connected with hyaline cartilage, ex: epiphyseal plate; synarthroses

symphyses

bones connected via fibrocartilage; amphiarthrodial, ex: intervertebral disc

Synovial joints (tissue? joint cavity? mobility?)

separated by synovial cavity; has a joint cavity; diarthroses

Types of synovial joints

plane, hinge, pivot, condylar, saddle, ball + socket

Bursae

flattened sacs filled with thin layer of synovial fluid; decreases friction; cushions muscles and increases mechanical effect

tendon sheath

elongated bursae that surrounds a tendon; common in “crowded areas” like the hands and feet

Relationship between mobility and stability

more mobility = less stability (and vice versa)

What is the weakest part of the skeleton?

synovial joints

articular surface

relative proportion of articular surfaces

ligaments purpose

prevents excessive movement, tighter ligaments = decreased range of motion BUT increased stability

effect of muscle tone on stability

stronger muscle = more stability

gliding

flat bones slide across each other

rotation

bones spins on a longitudinal axis

internal = toward midline

external = away from midline

extension

straighten muscle back to 0 degrees

flexion

decrease joint angle

hyperextension

extend beyond anatomical position (past 0 degrees)

abduction

away from midline

adduction

toward the midline

circumduction

flexion—> adduction —>extension—>abduction

supination

palm anterior (anatomical position)

pronation

palm posterior

inversion

tip sole medially

eversion

tip sole laterally

pronation of ankle

dorsiflex, evert, abduct

supination of ankle

plantar flexion, invert, adduct

protraction

bring forward

retraction

bring back

what is a unique motion of the jaw?

lateral excursion

opposition

thumb to other 4 fingers

reposition

return thumb to anatomical position

plane joint

gliding, nonaxial movement

hinge

unilateral, one bone is convex and the other is concave

pivot

unilateral, ex: c1 and c2

condylar

biaxial, ex: phalanges

saddle

biaxial, both sides have concave and convex portions

ball and socket

multiaxial, moves in all 3 planes, ex: shoulder

articular cartilage

reduces friction

joint cavity

synovial fluid

joint capsule

CT coating encapsulating cavity; retains fluid and protects; inner layer contains fibroblast cells that secrete synovial fluid

ligaments

connect bone to bone

synovial fluid

rich in albumin and hyaluronic fluid; reduces friction; viscous and slippery, nourishes cartilage

nerves and blood vessels of joints

aid in proprioception