Joints- ch 7 anatomy

joint definition

where 2 bones meet

how are joints classified?

according to the degree of movement, and by the tissue types (fibrous, cartilaginous, and synovial)

3 degrees of movement

immovable-synarthrotic, slightly moveable-amphiarthrotic, and freely moveable-diarthrotic

fibrous joints

a thin layer of dense regular CT(fibrous) that joins the bones. not rlly any movement.

fibrous joint examples

• sutures (like skull)

• syndesmoses (distal ends of tibia and fibula)

• gomphoses (where teeth meet facial bones)

cartilaginous joints +example

disks of fibrocartilage or hyaline cartilage between bones. slightly flexible and allows limited movement. disks help absorb shock and helps to equalize pressure between adjacent vertebrae. ex: intervertebral disks, symphysis pubis, and first rib of sternum

synovial joints

freely movable joints. articular ends covered with hyaline cartilage and a tubule capsule holding them in place. between the cartilage, there's a cavity full of synovial fluid to lubricate the joints, which is secreted by the synovial membrane

the 4 features of synovial joints

• articular cartilage (the hyaline cartilage between the 2 bones)

• articular capsule (in the knee, was the fibrous capsule surrounding the synovial membrane)

• joint cavity

• ligaments to reinforce it

ways joints move described by axis

• nonaxial: gliding and sliding, no movement within an axis though

• uniaxial: movement in 1 plane

• biaxial: movement in 2 planes

• multiaxial: movement in all directions

types of synovial joints

ball & socket, gliding, hinge, pivot joint, saddle joint, condyloid

ball and socket joint + examples

free movement in all planes, in shoulder and hip. egg shape in a cup

gliding/plane joints +examples

nearly flat articulating surfaces, slides bones past each, allowing for back and forth or even twisting motions. in wrist and ankle (carpals and tarsals), and even in vertebrae. think of it as rubbing 2 dominos on top of each other

hinge joint + examples

looks like a door hinge- how one cylinder fits into a spot. Only allows movement in one plane, and is for flexion and extension. elbow, knee, and phalanges

pivot joint + examples

kinda structured the upside way of a hinge joint, like half of a russian nesting doll, sorta attaches onto one bone and rotates. allows for rotation only. ex: proximal end of radius and ulna, and neck

saddle joint + examples

looks like a saddle, almost like if you fit a sine and a cosine graph together. opposing articular surfaces. ex: thumb. is biaxial

Condyloid joint (+ examples)

oval end that articulates with elliptical cavity. almost looks like an oval doorknob? allows for movement in 2 planes: back and forth and side-to-side, NO rotation. biaxial ex: where metacarpals and phalanges meet, and where the radius and carpals

what does movement involve?

contraction of a muscle attached to an immovable (fixed) end, origin, and a movable end, insertion

flexion

bending a joint, decreasing angle

extension

Straightening of a joint, increasing angle

dorsiflexion

flexing of foot

plantar flexion

Pointing of foot

abduction

lifting away from midline, usually upwards

adduction

lifting back down to midline, usually where the resting position is

rotation

twisting around a central axis, changes position without moving angle of joint

cirumduction

a complete circular motion

supination

turning hands upward

pronation

turning hands downward

eversion

sole of foot turns out

inversion

sole of foot turns in

retraction

moving a part backward (pulling chin back)

protraction

Moving a part forward (thrusting of chin)

elevation

pulling body part up- like shrugging shoulders or smiling

depression

lowering a body part- like drooping shoulders or frowning

hyperextension

excess extension that can result in injury

what joint is between the distal tibia and fibula

fibrous

disks of fibrocartilage between the articulating surfaces of the knee

menisci

fluid-filled sacs, sometimes associated with synovial joints. not actually part of the joint though

bursae

tendon sheath

bursa that wraps around a tendon