Fig. 2-5. The arrangement of fibers in muscles. The fibers are basically parallel (upper row) or pennate (or penniform), i.e., arranged as in a feather (lower row). A, Quadrilateral, e.g., pronator quadratus. B, Straplike, e.g., sartorius. C, Fusiform, e.g., flexor carpi radialis. D, Unipennate, e.g., flexor pollicis longus. E, Bipennate, e.g., rectus femoris. F, Multipennate, e.g., deltoid. Pennate muscles usually contain a larger number of fibers and hence provide greater power. Click for high resolution image.

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