The biceps connect to the radius in a way that facilitates both flexion and supination (outward rotation) of the forearm. The connection involves a 90-degree rotation of the muscle as it approaches the radius.
Here's a breakdown:
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Attachment Point: The distal (lower) end of the biceps muscle attaches to the radial tuberosity, a bony prominence on the radius bone located near the elbow joint.
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90-Degree Rotation: As stated in the reference, the biceps muscle undergoes a 90-degree twist as it connects to the radius. This rotation is crucial for supination.
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Functional Significance: This specific connection allows the biceps to effectively supinate the forearm. When the biceps contracts, it pulls on the radial tuberosity, rotating the radius and, consequently, the hand into a supinated (palm-up) position. This is in addition to flexing the elbow. The 90 degree rotation is critical to this motion.
| Feature | Description |
|---|---|
| Attachment Site | Radial tuberosity (a bony bump on the radius) |
| Muscle Rotation | Approximately 90 degrees as it approaches the radius, contributing significantly to the supination function. |
| Resulting Actions | Flexion and supination of the forearm. While the biceps aids in flexion, it is not the strongest flexor muscle. Its unique attachment gives it a primary role in supination. |
