9.1 - Joints & Their Classification

joint (articulation)

any point where two bones meet, whether or not the bones are mobile at that interface

arthrology

science of joint structure, function, and dysfunction

kinesiology

study of musculoskeletal movement

four major categories of joints

bony, fibrous, cartilaginous, and synovial

bony joint (synostosis)

immobile joint formed when the gap between two bones ossifies and they effectively become a single bone

bony joint (formation)

can form by the ossification of either fibrous or cartilaginous joints

bony joint (examples)

childhood (right and left mandibular bones; ilium, ischium, and pubis; and epiphysis and diaphysis of long bones), old age (first rib and sternum; two parietal bones along the sagittal suture)

fibrous joint (synarthrosis)

point at which adjacent bones are bound by collagen fibers that emerge from one bone, cross the space between them, and penetrate into the other

three types of fibrous joints

sutures, gomphoses, and syndesmoses

sutures and gomphoses (fibers)

fibers are very short and allow for little or no movement

syndesmoses (fibers)

fibers are longer and the attached bones are more mobile

sutures

immobile or only slightly mobile fibrous joints that closely bind the bones of the skull

three types of sutures

serrate sutures, lap sutures, and plane sutures

serrate sutures

appear as wavy lines along which the adjoining bones firmly interlock with each other by their serrated margins

serrate sutures (example)

coronal, sagittal, and lambdoid sutures

lap sutures (squamous sutures)

occur where two bones have overlapping beveled edges and appear as relatively smooth lines on the surface

lap sutures (example)

squamous suture

plane sutures (butt sutures)

occur where two bones have straight nonoverlapping edges

plane sutures (example)

intermaxillary suture

gomphosis

attachment of a tooth to its socket

periodontal ligament

fibrous ligament that consists of collagen fibers that extend from the bone matrix of the jaw into the dental tissue

periodontal ligament (function)

holds the tooth firmly in place and allows it to move or give a little under the stress of chewing

syndesmosis

fibrous joint at which two bones are bound by relatively long collagenous fibers

interosseus membrane

especially mobile syndesmosis that joints the shafts of the radius and ulna

interosseus membrane (function)

permits movements such as pronation and supination of the forearm

cartilaginous joint (amphiarthrosis)

joints in which two bones are linked by cartilage

two types of cartilaginous joints

synchondroses and symphyses

synchondrosis

joint in which the bones are joined by hyaline cartilage

synchondrosis (example)

temporary joint between the epiphysis and diaphysis of a long bone, attachment of the first rib to the sternum by a hyaline costal cartilage

symphysis

joint in which two bones are joined by fibrocartilage

symphysis (example)

pubic symphysis, invertebral discs