Answer
Based on the criterion of fascicle (bundle) arrangement muscle may be classified into five large groups:
1. Fusiform muscles: In these muscles the bundles are so arranged that the whole muscle tapers at both ends.
Examples re the gastrocnemius (calf muscle) and the biceps brachii.
2.Parallel muscles: In this class of muscles , the fascicles are of uniform width and have parallel
arrangement that in some cases present as a staplike structure.
Examples are the sarturious of the thigh and the rectus abdominis of the abdomen.
3. Triangular or convergent. In this class, the whole muscle has a fan-like shape--broad at one end and
narrow at the other.
Example : the pectoralis major
.
Work Step by Step
4, Circular muscles
These muscles form circular structures or sphincters
Examples are the obicularis oculi ; the external urethral sphincter ( voluntary)
and pyloric sphincter (smooth muscle).
5. The fifth class are the pennate or feather-shaped muscles. There are three subdivisions of this class:
a. Unipennate--all the fascicle approach the tendon from one side
Example: palmar interosseous
b. Bipennate : fascicles approach the tendon from both sides
e.g., rectus femoris of the thigh
c. Multipennate: shaped like a group of feathers with their quills meeting at one point
e.g., deltoid of shoulder.
