Joints (Ch 9)

joints

where rigid elements of the skeleton meet at or articulations

what greek root means joint?

arthro

functional classification

based on amount of movement

• synarthroses—immovable

• amphiarthroses—slightly movable

• diarthroses—freely movable

structural classification

based on material that binds bones together

• fibrous, cartilaginous, synovial

fibrous joints

immovable or slightly movable

types of fibrous joints

• sutures

• syndesmoses (tibiofibular joint)

• gomphoses

suture

occur between bones of the skull

gomphoses

tooth in a socket

syndesmoses

interosseous membrane between radius and ulna

synovial joints

most movable type of joint; fluid-filled joint cavity

what do synovial joints contain?

• articular cartilage

• joint (articular) cavity

• reinforcing ligaments

• sensory nerves

articular cartilage

type of hyaline cartilage covering the ends of opposing bones; absorbs compression

joint (articular) cavity

holds synovial fluid

reinforcing ligaments

thickened parts of the fibrous layer; job is to attach bone to bone

bursa (in the synovial joints)

a flattened fibrous sac lined by a synovial membrane; “pillow”

tendon sheath (in the synovial joints)

an elongated bursa that wraps around a tendon

bursae and tendon sheaths help with?

reducing friction

angular movements

• increase or decrease the angle between bones

• flexion/extension, abduction/adduction, circumduction

rotation

• movement around a bone’s long axis

• atlas and axis, hip and shoulder

elevation

lifting a body part superiorly

depression

moving the elevated part inferiorly

protraction

nonangular movement anteriorly; move forwards and out

retraction

nonangular movement posteriorly

supination (arm)

forearm rotates laterally, palm faces anteriorly “serving soup”

pronation (arm)

forearm rotates medially, palm faces posteriorly

opposition

thumb moves across the palm to touch the tips of other fingers

inversion (feet)

turns sole medially

eversion (feet)

turns sole laterally

dorsiflexion (feet)

lifting the foot so its superior surface approaches the shin

plantar flexion (feet)

depressing the foot, elevating the heel

rotation

turning a bone around the longitudinal axis

flexion

decreasing the angle between two bones, usually in the sagittal plane

extension

increasing the angle between bones, usually in the sagittal plane

abduction

moving a limb away from the body midline in the frontal plane

adduction

moving a limb toward the body midline; “adding to the body”

circumduction

moving a limb or finger so that it describes a cone in space

anterior cruciate ligament (ACL)

in front of the knee joint; prevents anterior sliding of the tibia

posterior cruciate ligament (PCL)

in the back of the knee joint; prevents posterior sliding of the tibia

locking the knee

stabilizes the knee joint without tiring the extensor muscles

joint tradeoff

more movable = less stable

less movable = more stronger

cartilaginous joints

bones are united by cartilage

what do cartilaginous joints contain?

• synchondroses

• symphyses

synchondroses

immovable joint between bones united by hyaline cartilage

symphyses

fibrocartilage unites bones; resists tension and compression (intervertebral discs, pubic symphysis)