Organization of Muscle Fibers

What are the patterns in which skeletal muscles are arranged?

parallel, convergent, pennate, and circular

How are skeletal muscle patterns determined?

by the shape or arrangement of the fibers relative to the direction of pull

How are muscles classified?

according to the shape or arrangement of their fibers relative to the direction of pull

Parallel muscle

muscle fascicles are parallel to the longitudinal axis

What are examples of parallel muscles?

biceps brachii and rectus abdominis

Convergent muscles

muscle fibers for a broad are but come together at a common point, such as a tendon, tendinous sheet, or raphe

What are examples of convergent muscles?

pectoralis major

Pennate Muscle

muscle fibers arrange like a feather; muscle fibers form an oblique angle to the tendon of the muscle

Unipennate

all muscle fibers are on the same side of the tendon

What is an example of a unipennate muscle?

extensor digitorum

Bipennate

muscle fibers are on both sides of the tendon

What is an example of a bipennate muscle?

rectus femoris

Multipennate

the tendon branches with the muscle

What is an example of a multipennate muscle?

deltoid muscle

Circular/Sphincter muscles

muscle fibers that form concentric rings; guard entrances and exits of long internal passageways, such as the digestive and urinary tracts

What are examples of circular muscles?

mouth and anus