Fasicular Arrangement

Structure

A muscle fascicle is a bundle of skeletal muscle fibers running parallel to each other, enveloped by a collagenous sheath called the perimysium. The arrangement and distribution of these fascicles, and hence, the orientation of the muscle fibers is directly related to the force, range, and direction of the movement of the muscle.

The fascicular arrangement of muscle can take many forms including the circular arrangement seen in muscles such as the orbicularis oris, the convergent (or triangular) arrangement seen in the pectoralis major, or the strap-like shape muscles seen in the sartorius muscle (Standring, 2016).

In this muscle, the biceps femoris muscle, the fascicles are organized in a parallel arrangement and lie along the long axis of the muscle within the “belly” of the muscle and will converge at either end where a tendon is then found. This arrangement of fibers results in what is called a fusiform muscle.

Function

The muscle fascicle bundles groups of muscle fibers together, resulting in greater cumulative strength of the muscle fibers. This facilitates in allowing the fascicle to produce more force during contraction. The arrangement of these fibers determines in what direction the muscle will “pull” as it contracts.

References

Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.