Joints Flashcards
joints
sites of union b/n bones or bodies of cartilage
consist of tissues which unite bones & cartilages at these sites
articular surfaces of a joint
surface areas of the apposing structures (generally)
fibrous joints
united by fibrous (connective) tissue
ex. distal tibiofibular joint of leg, joints b/n flat bones of skull (suture joints)
cartilagenous joints
bones are united by cartilage
2 classes: primary & secondary
primary cartilagenous joints (synchondroses)
apposing bones are joined by hyaline cartilage
ex. growth plates of growing long bones, union of first rib w/ manubrium of sternum
secondary cartilagenous joints
articular surfaces of bones covered by thin layers of hyaline cartilage, & hyaline cartilage plates are united by a layer of fibrocartilage
ex. manubriosternal joint, pubic symphysis, intervertebral discs
fibrocartilage
contains a very high concentration of collagen protein fibers in its matrix
dif type of collagen than that found in matrix of hyaline cartilage
synovial joints
artiuclation in which articular surfaces of bones are separated by a membrane-bound, fluid filled cavity
provide greatest degree of movement b/n bones at expense of stability of joint
degree of movement is inversely proportional to its stability
articular cartilage
thin layer of hyaline cartilage that covers articular surfaces of bones in a synovial joint
synovial membrane
lines fluid-filled cavity between synovial joints, except where the cavity is bored by articular cartilage
synovial fluid
fluid secreted by the highly vascular synovial membrane of a synovial joint
rich in hyaluronic acid
has consistency of thick machine oil
functions as an excellent lubricant b/n bones
fibrous capsule
dense, fibrous connective tissue that encloses an entire synovial joint
articular disc (structure)
piece of fibrocartilage interposed like a shelf or pad b/n articulating surfaces of a synovial joint
around its circumference, anchored to the fibrous capsule of the joint
menisci
articular disc of a synovial joint that’s incomplete & crescent shaped
ex. knee joint
functions of articular discs & menisci
shock absorption
assistance in providing more even distribution of weight & synovial fluid
improvement of the fit of articular surfaces
plane joints
type of synovial joint
apposed articular surfaces are flat or almost flat & the boens slide on one another
ex. sternoclavicular & acromioclavicular joints
hinge joints
type of synovial joint
resemble the hinge on a door
articular surfaces are molded to each othe rin such a way to allow movement in one plane (uniaxial)
allow flexion & extension
ex. elbow, knee, ankle, & interphalangeal joints
pivot joints
type of synovial joint
movement occurs around one axis (uniaxial)
a central bony pivot is surrounded by a ligamentous ring & rotation is the only movement possible
movement occurs as the pivot turns within the ring, or as the ring turns around the pivot, around the longitudinal axis
ex. atlantoaxial & proximal & distal radioulnar joints
condylar (ellipsoid) joints
type of synovial joint
biaxial joints that allow movement around 2 principla axies which are at right angles to each other
an elliptical convex articular surface fits into an elliptical concave aritcular surface
the movements of flexion-extension, abduction-adduction take place
a combination of these movements allows circumduction around a third axis, but rotation around the third axis is not possible b/c of the ellipsoid shape of the bones
ex. radiocarpal (wrist) & metacarpophalangeal (knuckle) joints
saddle joint
type of synovial joint
biaxial b/c two principal axes of movement
articular surfaces are saddle-shaped
movements include flexion-extension, abduction-adduction, & circumduction (same as condylar)
modest amount of axial rotation is seen as well
ex. carpometacarpal joint of thumb
ball & socket joints
type of synovial joints
ball-shaped head of one bone fits into the socket-like concavity of another
arrangement permits maximum degree of all movement (flexion-extension, abduction-adduction, circumduction, & rotation
greater depth of socket = more stable joint = more limited movement
ex. shoulder & hip joints
3 main factors that determine stability of a joint
shape of articular surfaces (ex. hip)
ligaments (ex. knee)
tone of muscles around the joint (ex. shoulder)
innervation of synovial joints
Hilton’s law: the nerve supplying a joint also supplies the muscles that act across the joint & the skin covering the articular insertions of these muscles
