Arthrology
Classification:
Fibrous joints — Immobile joints, united by fibrous tissue, may ossify with age.
Three types are recognized:
1. Suture = Undulating seams between bones of the skull
2. Gomphosis = Tooth in an alveolus, united by periodontal ligament
3. Syndesmosis = Bones joined by ligaments, e.g., (radius & ulna) and (tibia & fibula)
Cartilaginous joints — Immobile joints, united by cartilage, ossify with age.
Two types are recognized:
1. Symphysis = Fibrocartilage union, e.g., pelvic symphysis; mandibular symphysis.
2. Synchondrosis = Hyaline cartilage union, e.g., physis
Synovial joints — mobile joints, fibrous tissue enclosing a synovial cavity Classified on the basis of.
Number of bones:
Simple joint = formed by two bones, e.g., shoulder joint
Compound joint = formed by more than two bones, e.g.,
elbow joint, carpal joint
Shape:
Hinge joint = movement in one plane
Ball & socket joint = capable of circumduction
Plane joint = gliding action, e.g., vertebral articular processes
Synovial Joint Structure:
Joint feature
Articular (hyaline) cartilage covers the opposing surfaces of the bones
Synovial membrane lines a synovial cavity that separates the bones
the membrane secretes synovial fluid into the cavity
Fibrous (collagenous tissue) layer located external to synovial membrane
Mechanically joins the bones, blends with periosteum selectively thickened to form ligaments
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Additional features found in some synovial joints...
=> Meniscus = fibrocartilage in the synovial cavity, interposed between the bones.
=> Internal ligaments that appear to be within the joint cavity.
=> Fat pads between the fibrous & synovial layers produce synovial folds that may protrude into the joint cavity.
Types of fibrous joint
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(a) Syndesmosis
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(b) Suture
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(c) Gomphosis
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Synovial joint
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Stifle joint of dog
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