8-1. Classification of Joints Flashcards
articulations
sites where two or more bones come together; give the skeleton mobility and hold it together
What are the classifications of joints?
functional - based on degree of movement
structural - based on material binding bones together
What are the functional classifications of joints?
synarthrosis (immovable)
amphiarthrosis (slightly moveable)
diarthrosis (freely moveable)
synarthrosis
an immovable joint. eg. cranial sutures
amphiarthrosis
a slightly movable joint. eg. intervertebral discs
diarthrosis
freely movable joints. eg. shoulder
What are the structural classifications of joints?
fibrous
cartilaginous
synovial
fibrous joints
bones joined together by fibrous tissue, held together tightly. No joint cavity present. Functionally, most are synarthrotic
What are the three types of fibrous joints?
sutures
syndesmosis
gomphosis
sutures
seams between skull bones; bind bones tightly together yet allow them to grow at edges during youth. By middle age, fibrous tissue ossifies and skull bones fuse into a unit
syndesmosis
bones connected by ligament; amount of movement depends on length of connecting fibers.
(eg. ligament connecting tibia and fibula is short (synarthrosis); one connecting radius and ulna permits rotation (amphiarthrosis))
gomphosis
peg-in-socket fibrous joint where tooth sits in bony alveolar socket; held by periodontal ligament (synarthrosis)
cartilaginous
bones held together by cartilage, no joint cavity present
What are the two types of cartilaginous joints?
synchondroses
sympheses
synchondroses
bar of hyaline cartilage unites bones (synarthrosis)
eg. epiphyseal plate, joint between first rib and sternum
symphyses
articulating bones fused to pad of fibrocartilage that acts as shock absorber and permits limited movement (amphiarthrosis)
(eg. intervertebral discs, pubic symphysis)
synovial joints
bones separated by fluid filled joint cavity; all are diarthroses
What are the five distinguishing features of synovial joints?
- articular cartilage (smooth hyaline cartilage covers bone surfaces at joints)
- joint (synovial) cavity (space between bones; contains small amount of synovial fluid)
- articular capsule (joint cavity enclosed by 2 layered capsule; outer fibrous capsule and inner layer is a synovial membrane)
- synovial fluid (small amount of slippery fluid within joint capsule that lubricates and reduces friction between cartilages)
- reinforcing ligaments (joints reinforced and strengthened by a number of band-like ligaments)
What are some other features that some synovial joints have?
menisci
bursa
tendon sheath
menisci
discs of fibrocartilage separating the articular surfaces of some synovial joints (knee, jaw). make joint more stable and minimize wear and tear
bursa
flattened fibrous sacs lined with synovial membrane and containing a thin film of lubricating synovial fluid. common where tendons, ligaments, muscles or bones rub together
tendon sheath
elongated bursa that wraps around a tendon subjected to friction
What are the six types of synovial joints?
plane joint hinge joint pivot joint condyloid joint saddle joint ball and socket joint
plane joint
flat articular surfaces allow short gliding motions (eg. intercarpal, intertarsal)
