What are joints Are the bodys hinges There
What are joints? • Are the body’s hinges • There are three types • Fixed or fibrous joints • Slightly movable or cartilaginous joints • Freely movable or synovial joints
Fixed, or fibrous joints Characteristics • No movements Structure • Fibrous tissue between the ends of the bone e. g. sutures in the skull, pelvic girdle bones.
Slightly moveable, or cartilaginous joints Characteristics • Slightly moveable, moves by compression of the cartilage. Structure • Pad of white fibrocartilage between the bones e. g. spine
Freely moveable, or synovial joints • In a freely movable joint ends of the bones are mostly covered by hyaline cartilage. • The cartilage helps to reduce friction and acts as a shock absorber during movement. • Ligaments are needed to bind the bones together and help prevent dislocation. • The space between the bones is called the joint cavity and is enclosed by a capsule of fibrous tissue.
Freely moveable, or synovial joints Five different types 1. Ball and socket A ball and socket joint allows for radial movement in almost any direction. They are found in the hips and shoulders
• Ellipsoid joints are similar to a ball and socket joint. They allow the same type of movement to a lesser magnitude. • The wrist is an ellipsoid joint
2. Hinge A hinge joint allows extension and retraction of an appendage
3. Gliding • In a gliding or plane joint bones slide past each other. • Midcarpal and midtarsal joints are gliding joints
4. Pivot • Pivot joints allow rotation around an axis. • The neck and forearms have pivot joints. In the neck the occipital bone spins over the top of the axis. • In the forearms the radius and ulna twist around each other.
5. Saddle A saddle joint allows movement back and forth and up and down, but does not allow for rotation like a ball and socket joint.
Joint Movements • • Flexion- bending movement that decreases an angle (elbow, knee) Extension- increasing the angle (straightening the arm) Abduction- moving a bone away from the midline (holding arms straight out at sides) Adduction- moving bone towards midline (returning arms to the side) Circumduction- making circles with your arms Rotations- moving bone around a central axis (shaking head no) Supination- Palm up (ulna and radius are parallel)
• • • Pronation- Palm down (ulna and radius cross) Eversion- moving sole of foot outward (walk like a penguin) Inversion- moving sole of foot inward (“pigeon toed”) Protraction- moving part of body forward on a plane parallel to the ground (sticking your bottom jaw out) Retraction- moving part of body back on a plane parallel to the ground (putting jaw back) Elevation- moving body part upward (raising your hand) Depression- moving body part downward Gliding- allows one bone surface to slide over another (bend your back) Opposition- movement of the thumb
Angular Movements
Rotational Movements
Special Movements
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