Extension in anatomy refers to a movement that increases the angle between body parts at a joint, typically straightening the joint.
Here's a more detailed explanation:
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Definition: Extension is fundamentally about increasing the angle between bones that articulate at a joint. It is the opposite of flexion, which decreases the angle.
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Mechanism: This increase in angle is achieved by the contraction of specific muscles that pull the bones away from each other, effectively straightening the limb or body part.
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Examples:
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Extending the arm: Straightening your arm at the elbow joint is an example of extension. The angle between your upper arm (humerus) and forearm (radius and ulna) increases.
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Extending the leg: Straightening your leg at the knee joint is another common example.
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Trunk Extension: Arching your back, increasing the angle between your abdomen and back.
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Extension Beyond Anatomical Position (Hyperextension): In some joints, extension can go beyond the normal anatomical position (straight). This is called hyperextension.
- Example: Bending your head backward so you are looking at the ceiling is hyperextension of the neck.
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Anterior vs. Posterior in Limbs: For limbs, especially the upper limb, movements are often described relative to the front (anterior) and back (posterior) of the body. Extension generally involves posterior movement of the limb.
In summary, extension is a crucial movement in the body that allows us to straighten our limbs and trunk, enabling a wide range of activities.
