9) PATTERN OF FASCICLE ORGANIZATION

• Parallel

• Circular

• Fusiform

• Triangular

• Pennate

  • Unipennate

  • Bipennate

  • Multipennate

PATTERN OF FASCICLE ORGANIZATION

Parallel

• Fascicles parallel to longitudinal axis of muscle, terminate at either end in flat tendons

Example: sternohyoid muscle

Circular

• Fascicles in concentric circular arrangement from sphincter muscles that enclose an orifice

Example: orbicularis oculi

Fusiform

• Fascicles nearly parallel to longitudinal axis of muscle; terminate in flat tendons; muscle tapers toward tendons where diameter is less than at belly

Example: digastric muscle

Triangular

• Fascicles spread over broad area converge at thick central tendon; gives muscle a triangular appearance

Example: pectoralis major muscle

Pennate

Short fascicles in relation to total muscle length, tendon extend nearly entire length of muscle

• Unipennate

• Bipennate

• Multipennate

3 Types of Pennate

Unipennate

• Fascicles arranged on only one side of tendon

Example: extensor digitorum longus

Bipennate

• Fascicles arranged on both sides of centrally positioned tendons

Example: rectus femoris

Multipennate

• Fascicles attach obliquely from many directions to several tendons 

Example: Deltoid

Intramuscular Injections (Clinical Correlation)

• Penetrates the skin and subcutaneous layer to enter the entire muscle itself 

• Preferred if prompt absorption is desired