the skeletal system - chp 8 joints
DESCRIPTION
pptTRANSCRIPT
-
JointsJoints (articulations), the sites where two or more bones meet, have two fundamental functions:Give skeleton mobilityHold skeleton together Joints are classified by structure & function: Structure: focused on the material that binds the bones together & whether a joint cavity is presentFunction: Based on the amount of movement allowed at the joint.
-
Joints: Structural ClassificationFocuses on material binding joint and whether or not a joint cavity is presentThree structural categories:Fibrous: joined by fibrous tissue, no joint cavity, generally immovable or only slightly movable (based on length of connective tissue fibers)Sutures, Syndemoses & GomphosesCartilaginous: articulating bones are united by cartilage, lack a joint cavitySynchondroses or SymphysesSynovial: articulating bones are separated by a fluid-containing joint cavity, substantial freedom of movementmajority of joints fit into this category including all limb joints
-
Fibrous JointsSutures (seams) Only between bones of skullCompletely filled with short connective tissue to prevent movement but allow growthOssifies at middle age and become synostoses (bony junctions) Syndesmoses Connected by a ligament, length can vary and determine mvmntEx) tibia/fibula (some give) v. radius/ulna (rotation permitted)Gomphosespeg-in-socketOnly example is teeth in bony alveolar socketFibrous connection is short periodontal ligament
-
Cartilaginous JointsSynchondroses:Bar or plate of hyaline cartilage unites bonesEx) ephipheseal plates in long bones of children (eventually become synostoses) and immovable joint of 1st rib costal cartilage to manubrium
Symphyses: (growing together)Articular surfaces covered with articular hyaline cartilage which is fused to pad or plate of fibrocartilageFibrocartilage acts as a shock absorber and permits limited movement, for strength and flexibilityEx) Intervertebral disks and pubis symphysis
-
The Synovial JointFive Distinct FeaturesArticular cartilageJoint (synovial) cavityArticular capsuleSynovial fluidReinforcing ligaments
-
Structures Associated with the Synovial JointBursae flattened fibrous sacsLined with synovial membranesFilled with synovial fluidNot actually part of the jointTendon sheathElongated bursa that wraps around a tendon
-
Types of Synovial Joints Based on Shape I
-
Types of Synovial Joints Based on Shape II
-
Movements Allowed by Synovial Joints
-
Joints: Functional ClassificationBased on amount of movement allowed in the jointThree functional categories:Synarthroses: immovable majority of fibroussome cartilaginousAmphiarthroses: slightly movable some cartilaginousDiarthroses: freely movable All synovial
-
Joint InjuriesSprains: ligaments reinforcing a joint are stretched or torn; common in lumbar region of spine, the ankle & the kneeCartilaginous injuries: overuse damage to articular cartilage or tearing of knee menisci, usually due to intense athletic use; often hear snap & pop noiseDislocations: bones are forced out of alignment; usually accompanied by sprains, inflammations & joint immoblilization; Usually the result of a serious fall or contact injury
-
Inflammatory & Degenerative ConditionsBursitis: inflammation of bursa; usually due to a physical blow or friction
Tendonitis: inflammation of tendon sheaths; usually due to overuse
Arthritis: broad term applying to >100 types of inflammatory/degenerative diseases that damage joints; combined it is the most widespread, crippling disease in the U.S.
-
ArthritisOsteoarthritis (OA): most common chronic arthritis; wear & tear arthritis; develops in ~85% of Americans; probably related to normal aging process, believed that normal joint use promotes the release of metalloproteinase enzymes that break down articular cartilage
Rheumatoid Arthritics (RA): Autoimmune disease, immune system attacks bodily tissue; Initial trigger unknown, may be linked to streptococcus bacterium, affects ~1% of Americans will be affected; starts off with joint tenderness and stiffness, onset is usually bilateral; periods of flare-ups & remissions
Gouty Arthritis: Increase in uric acid in blood sometimes results in needle-like urate crystals in the soft tissues of joints; this triggers an inflammatory response or a gout attack; typically affects one joint, usually base of the big toe
****