Joints Joints (articulations) - the sites where two or more bones meet; weakest parts of skeleton....
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Transcript of Joints Joints (articulations) - the sites where two or more bones meet; weakest parts of skeleton....
![Page 1: Joints Joints (articulations) - the sites where two or more bones meet; weakest parts of skeleton. Two fundamental functions: – Give skeleton mobility.](https://reader035.fdocuments.us/reader035/viewer/2022062423/56649c9e5503460f9495e009/html5/thumbnails/1.jpg)
Joints• Joints (articulations) - the sites where two or
more bones meet; weakest parts of skeleton.Two fundamental functions:– Give skeleton mobility– Hold skeleton together; sometimes playing a
protective role.
• Joints are classified by structure & function: – Structure: focused on the material that binds the
bones together & whether a joint cavity is present– Function: Based on the amount of movement
allowed at the joint.
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Joints: Structural Classification• Focuses on material binding joint and whether or not a joint
cavity is present• Three structural categories:– Fibrous:
• joined by fibrous tissue, no joint cavity, generally immovable or only slightly movable (based on length of connective tissue fibers)
• 3 Types of Fibrous Joints: Sutures, Syndesmoses & Gomphoses
– Cartilaginous: • articulating bones are united by cartilage, lack a joint cavity• 2 Types of Cartilaginous Joints: Synchondroses or Symphyses
– Synovial:• articulating bones are separated by a fluid-containing joint cavity,
permits substantial freedom of movement. Freely movable diarthroses
• majority of joints fit into this category including all limb joints
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Fibrous Joints• Sutures (“seams”)
– Only between bones of skull– Completely filled with short connective tissue continuous w/ periosteum
to prevent movement but allow for growth– Ossifies at middle age and become “synostoses” (bony junctions); moving
cranial bones would damage brain – protective adaptation. • Syndesmoses (syndesmos = ligament)
– Bones connected by a ligament, length can vary & determines movement– Prevents true movement, fuctionally an immovable joint/synarthrosis– Ex: tibia/fibula (some “give”) v. radius/ulna (rotation permitted)
• Gomphoses– “peg-in-socket” fibrous joint– Only example – articulation of teeth in bony alveolar sockets– Fibrous connection is short periodontal ligament
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Cartilaginous Joints• Synchondroses:
– Bar or plate of hyaline cartilage unites bones @ synchondrosis (junction of cartilage)
– Ex: ephipheseal plates connecting diaphysis & epiphysis in long bones of children (eventually become synostoses) and immovable joint of 1st rib costal cartilage to manubrium
• Symphyses: (“growing together”)– Articular surfaces of bone are covered with articular hyaline
cartilage which is fused to pad or plate of fibrocartilage– Fibrocartilage acts as a shock absorber and permits limited
movement, for strength and flexibility– Ex) Intervertebral disks and pubis symphysis of pelvis
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The Synovial JointThe Synovial Joint
Five Distinct Features1.Articular cartilage2.Joint (synovial) cavity3.Articular capsule4.Synovial fluid5.Reinforcing ligaments
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Structures Associated with the Synovial JointStructures Associated with the Synovial Joint
Bursae – flattened fibrous sacs
Lined with synovial membranes
Filled with thin film of synovial fluid
Not actually part of the joint
Generally found in places of prone to friction. Ex: shoulder joint
Tendon sheath
Elongated bursa that wraps around a tendon
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Types of Synovial Joints Based on Shape ITypes of Synovial Joints Based on Shape I
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Types of Synovial Joints Based on Shape IITypes of Synovial Joints Based on Shape II
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Movements Allowed by Synovial Joints
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Joints: Functional Classification
• Based on amount of movement allowed in the joint• Three functional categories:
– Synarthroses: immovable • majority of fibrous• some cartilaginous
– Amphiarthroses: slightly movable • some cartilaginous
– Diarthroses: freely movable • All synovial
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Joint Injuries• Sprains: ligaments reinforcing a joint are
stretched or torn; common in lumbar region of spine, the ankle & the knee
• Cartilaginous injuries: overuse damage to articular cartilage or tearing of knee menisci, usually due to intense athletic use; often hear “snap & pop” noise
• Dislocations: bones are forced out of alignment; usually accompanied by sprains, inflammations & joint immoblilization; Usually the result of a serious fall or contact injury
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Inflammatory & Degenerative Conditions
• Bursitis: 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.
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Arthritis• Osteoarthritis (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