Joints

Question 1

joints

Answer 1

sites of union b/n bones or bodies of cartilage

consist of tissues which unite bones & cartilages at these sites

Question 2

articular surfaces of a joint

Answer 2

surface areas of the apposing structures (generally)

Question 3

fibrous joints

Answer 3

united by fibrous (connective) tissue

ex. distal tibiofibular joint of leg, joints b/n flat bones of skull (suture joints)

Question 4

cartilagenous joints

Answer 4

bones are united by cartilage

2 classes: primary & secondary

Question 5

primary cartilagenous joints (synchondroses)

Answer 5

apposing bones are joined by hyaline cartilage

ex. growth plates of growing long bones, union of first rib w/ manubrium of sternum

Question 6

secondary cartilagenous joints

Answer 6

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

Question 7

fibrocartilage

Answer 7

contains a very high concentration of collagen protein fibers in its matrix

dif type of collagen than that found in matrix of hyaline cartilage

Question 8

synovial joints

Answer 8

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

Question 9

articular cartilage

Answer 9

thin layer of hyaline cartilage that covers articular surfaces of bones in a synovial joint

Question 10

synovial membrane

Answer 10

lines fluid-filled cavity between synovial joints, except where the cavity is bored by articular cartilage

Question 11

synovial fluid

Answer 11

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

Question 12

fibrous capsule

Answer 12

dense, fibrous connective tissue that encloses an entire synovial joint

Question 13

articular disc (structure)

Answer 13

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

Question 14

menisci

Answer 14

articular disc of a synovial joint that’s incomplete & crescent shaped

ex. knee joint

Question 15

functions of articular discs & menisci

Answer 15

shock absorption

assistance in providing more even distribution of weight & synovial fluid

improvement of the fit of articular surfaces

Question 16

plane joints

Answer 16

type of synovial joint

apposed articular surfaces are flat or almost flat & the boens slide on one another

ex. sternoclavicular & acromioclavicular joints

Question 17

hinge joints

Answer 17

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

Question 18

pivot joints

Answer 18

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

Question 19

condylar (ellipsoid) joints

Answer 19

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

Question 20

saddle joint

Answer 20

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

Question 21

ball & socket joints

Answer 21

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

Question 22

3 main factors that determine stability of a joint

Answer 22

shape of articular surfaces (ex. hip)

ligaments (ex. knee)

tone of muscles around the joint (ex. shoulder)

Question 23

innervation of synovial joints

Answer 23

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