fascicle arrangement

circular

-fascicles are arranged in a circle around an opening and act as sphincters to close the opening

-ex: orbicularis oris and orbicularis oculi

convergent

-broadly distributed fascicles converge at a single tendon

-triangular

-ex: pectoralis major and pectoralis minor

parallel

-fascicles lie parallel to one another and to the long axis of the muscle

-trapezium, rhomboidal, and quadrate

-ex: trapezius, rhomboideus, and rectus abdominis

pennate

-fascicles originate from a tendon that runs the length of the entire muscle.

1. unipennate: fascicles are on only one side of the tendon (ex: palmar interosseus and semimembranosus)

2. bipennate: fascicles are on both sides of the tendon (ex: rectus femoris)

3. multipennate: fascicles are arranged at many places around the central tendon. they are spread out at angles to many smaller tendons (ex: deltoid)

fusiform

-fascicles lie parallel to the long axis of the muscle. the belly of the muscle is larger in diameter than the ends

-ex: biceps brachii (two-headed; shown) and triceps brachii (three-headed)