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Joints

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Joints (articulations)
where two or more bones meet
Function of Joints
give skeleton mobility and hold skeleton together
Three Classifications of Joints
synarthrotic, amphiarthrotic, diathrotic
Synarthroses
immovable joints
Amphiarthroses
slightly movable joints
Diarthroses
freely movable joints
Suture
an immovable joint (especially between the bones of the skull) that ossify during middle age
Structural Classification of Joints
focuses on the material binding the bones together and whether or not a joint cavity is present. There are fibrous, cartilaginous, and synovial joints
Fibrous Joints
synarthrotic joints connect bone to bone with dense fibrous connective tissue. There are sutures, gomphoses, and sydesmoses
Gomphoses
fibrous joints consisting of pegs, sockets they fit into and the ligaments that hold them; is an amphiarthrosis
Syndemoses
structural classification; fibrous joint; bones connected by ligaments; synarthrotic (tibia/fibula) to amphiarthrotic (ulna/radius)
Cartilaginous Joints
Have no joint cavity, connects bones to bone by cartilage.
Examples of Cartilaginous Joints
growth plates, disks between vertebrae and the pelvic symphysis
Types of Cartilaginous Joints
synchondroses, symphyses
Synchondroses
bones joined by hyaline cartilage; synarthrotic
Symphyses
bones are connected by a broad, flat disc of fibrocartilage; amphiarthrotic
Synovial Joints
the most movable joints of the body; diarthrotic each contains a fluid-filled joint cavity
Distinguishing Factors of Synovial Joints
articular cartilage, joint (synovial) cavity, and articular (joint) capsule
Articular cartilage
hyaline cartilage that covers ends of long bones; decreases friction
Joint cavity
filled with synovial fluid and provides constant lubrication during movement
Articular capsule
external fibrous capsule (dense irregular connective tissue) and internal synovial membrane (loose connective tissue)
Synovial fluid
plasma and hyaluronic acid lubricates, nourishes, and keeps the joint moveable
Distinguishing Features of Synovial Joints
three types of reinforcement ligaments; capsular, extracapsular, intracapsular
Capsular
part of fibrous capsule
Extracapsular
outside the capsule
Intracapsular
deep to capsule; covered by synovial membrane
Bursae
flattened fibrous sacs lined with synovial membranes, common where ligaments, muscles, skin, and tendons rub together
Function of Bursae
act as a "ball-bearing"
Tendon sheath
Elongated bursae; urrounds a tendon and found along long tendons in bone
Stabilizing Factors in Synovial Joints
shapes of articular surface, ligament number and location, and muscle tone
Shape of Articular Surface
plays a minor role in mobility but play major role in stabilizing synovial joints
Ligament Number and Location
plays a limited role in synovial joint stabilization, but the more ligaments there are, the stronger the joint
Stretching Ligaments
Once you stretch a ligament, it stays stretched. After stretched more than 6% of its original length, ligaments snap
Muscle Tone
plays a major role in stabilizing synovial joints and keeping tendons that cross the joint taut. Especially key in the knee, shoulder, and arches of foot)
Movement of Synovial Joints
muscle attachments across a joint
Origin of Synovial Joints
attachment to the immoveable (or less moveable) bone
Insertion of Synovial Joints
attachment to the moveable bone
Where Synovial Joint Movements Occur
transverse, frontal, or sagittal planes
Muscle Contraction
causes the insertion to move toward the origin