Answer
Muscles can be divided into the following types by the criterion of fascicle orientation:
fusiform, parallel, circular, triangular( convergent, unipennate, bipennate and multipennate
1, Fusiform; In this type muscles appear thick in the middle and tapering at both ends. These muscles are very strong, Examples are the gastrocnemius and the biceps brachii.
2. Parallel: These muscles have parallel bundles and the whole muscle is nearly uniform in width. Examples are the rectus abdominis, and the sartorius. Examples of two that are semi-rectangular (quadrilateral) in shape are the masseter, and the quadratus lumborum.
3. Circular ( sphincters). These muscles form rings around some body openings and control the entry and exit of materials into those passages. When they contract they constrict the openings and restrict or inhibit passage of substances; when the relax they allow passage of materials. Examples of this class are the obicularis oculi of the eye, the pyloric valve of the digestive tract ( smooth muscle), and the obicularis oris of the mouth.
Work Step by Step
4, Triangular or convergent. These muscle are wide at one end and narrower at the other. These muscles
are strong. An example is the pectoralis major.
5. Pennate muscles. These are feather-shaped muscles. Their fiber bundles attach to a tendon than runs
the entire length of the muscle
a. Unipennate: All the muscle fascicles attach to the tendon on one side. Examples: extensor
digitorum longus, and the posterior tibialis muscles
b. Bipennate: In these muscles, the fascicles insert into the tendon on both sides. An examples is the
rectus femoris.
c. Multipennate:. These present like a group of feathers with their quills inserted at the same area on
the tendon. An examples is the deltoid.
