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)
hinge joint
cylindrical projection of 1 bone fits into trough of other; allows only flexion/extension
(eg. elbow (btwn radius and ulna), btwn flanges)
pivot joint
rounded end of 1 bone protrudes into ring of bone/ligament on another; only allows rotation of 1 bone around axis
(eg. dens, radius and ulna)
condalyoid joint
oval surface of 1 bone fits into matching depression on other; permits all angular motions
(eg. knckle, wrist, atlas and occipital condyles)
saddle joint
saddle-shaped articular surfaces fit together, concave to convex, allow greater freedom of movement
(eg. base of thumb (1st CMC joint - carpal to metacarpal)
ball and socket joint
spherical head of 1 bone fits into cuplike socket of other; universal movement is allowed
(eg. shoulders, hips)
Which joint is the largest and most complex in the body?
the knee joint - allows extension, flexion and some rotation
Which joint is the most movable?
the shoulder joint - ball and socket joint that has sacrificed some stability to be the most freely movable
femoropatellar joint
a plane joint that allows the patella to glide across the distal end of the femur during knee movements
tibiofemoral joint
between the femoral condyles above and the C-shaped menisci of tibia below. It acts primarily as a hinge but allows some rotation when the knee is partially flexed
What is unique about the knee joint?
joint cavity is only partially enclosed by capsule - anteriorly, 3 broad ligaments run from patella to tibia below
cruciate ligaments
cross each other in the notch below femoral condyles and help prevent anterior-posterior displacement when we stand
collaterol ligaments
prevent lateral or medial rotation when knee is extended
The knee is heavily reinforced by ___ and ___
muscle tendons and at least a dozen bursae
___ blows are most dangerous to the extended knee
Lateral - tear collateral ligament, medial meniscus and anterior cruciate ligament
How is the shoulder joint formed?
large rounded head of the humerus fits into shallow glenoid cavity of scapula, slightly deepend by a rim of fibrocartilage. The articular capsule is thin and loose; the few ligaments reinforcing are on the anterior surface
What provides stability to the shoulder joint?
muscle tendons crossing the shoulder - superstablizer is the tendon of the long head of the bicep brachii, securing the head of humerus against the glenoid cavity
rotator cuff
made of four tendons and associated muscles, encircles the shoulder joint and blends with the articular capsule
What 4 muscles make up the rotator cuff?
subscapularis
supraspinatus
infraspinatus
teres minor
