Skeletal Muscle Fascicle Alignment

Key Organizational Points:

Fascicles

Groups of muscle cells bound by connective tissue

Fascicle alignment determines the strength and direction of force that muscles exert

Midline of the body

Separates right and left halves

Parallel muscles

Fascicles run in parallel
Appear either strap-like or spindle-shaped
The belly (aka, gaster) is the central portion of the muscle
When parallel fascicles contract, the muscle length shortens

Circular muscle

Fascicles are arranged around a circular opening
When they contract they close off openings (such as the mouth)

Convergent muscle

Fascicles converge at a tendon
When they contract, the muscle can shorten along multiple axes

Pennate muscles

Fascicles insert obliquely at a central tendon
When they contract, the muscle shortens

Types of pennate muscles: Bipennate muscle has fascicles that insert on both sides of the tendon Unipennate muscle has fascicles that insert on only one side of the tendon Multipennate muscle (such as the deltoid of the shoulder) comprises multiple tendons with oblique fascicle insertions

Skeletal Muscle Fascicle Alignment

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