Muscle fascicle

A muscle fascicle is a bundle of skeletal muscle fibers surrounded by perimysium, a type of connective tissue.^[1]

Muscle fascicle
Structure of a skeletal muscle. (Fascicle labeled at bottom right.)
Details
Part of	Skeletal muscle
Identifiers
Latin	fasiculus muscularis
TA2	2006
TH	H3.03.00.0.00003
FMA	76740
Anatomical terminology [edit on Wikidata]

Not to be confused with Nerve fascicle.

Structure

Muscle cells are grouped into muscle fascicles by enveloping perimysium connective tissue.^[1] Fascicles are bundled together by epimysium connective tissue.^[1] Muscle fascicles typically only contain one type of muscle cell (either type I fibres or type II fibres), but can contain a mixture of both types.^[2]

Function

In the heart, specialized cardiac muscle cells transmit electrical impulses from the atrioventricular node (AV node) to the Purkinje fibers – fascicles, also referred to as bundle branches.^{[citation needed]} These start as a single fascicle of fibers at the AV node called the bundle of His that then splits into three bundle branches: the right fascicular branch, left anterior fascicular branch, and left posterior fascicular branch.

Clinical significance

Myositis may cause thickening of the muscle fascicles.^[3] This may be detected with ultrasound scans.^[3]

Muscle fascicle structure is a useful diagnostic tool for dermatomyositis. Myocytes towards the edges of the muscle fascicle are typically narrower, while those at the centre of the muscle fascicle are a normal thickness.^[4]

Muscle fascicles may be involved in myokymia, although commonly only individual myocytes are involved.^[5]

See also

• Deep fascia
• Endomysium
• Epimysium