Question

At the conclusion of this chapter, the student should be able to: Describe the relationship between the skeletal muscle’s fiber arrangement and its function.

Answer 1

Skeletal muscle fiber arrangement and its function.

Skeletal muscles are voluntary muscles which are present on bones . They change the limb position, help in walking, controlling body activities, controlling urination, defeacation. etc

Skeletal muscle fibers are arranged in various arrangements, So to function differently. This arrangement is based on axis of force generation of muscle ie from origin to insertion of muscle.

Arrangements are longitudinal,unipennate, and multipennate.

Longitudnal: Fascicles are parallel with axis of force generation and muscle fibers run longitudnally.. Eg biceps brachi , orbicularis occuli.

Unipennate :when all fibers orient at same angle in relation to axis of force. For eg. Vastus lateralis gets attached to patella and is a powerful extensor of knee joint.

Multipennate: Fibers in multipennate muscles are arranged at multiple angles in relation to the axis of force generation. It is most common arrangement . It is used for multiple function For eg. Trapezius and deltoid.

Trapezius can elevate or depress the shoulder blades.

Deltoid is a traingular muscle on shoulder. it has anterior fibers which flexes and medially rotates the arm by pulling the humerus towards the clavicle. The lateral fibers which causes abduction of arm ie pulls outwards by pulling the humerus toward the acromion process and posterior fibers which extends and laterally rotates the arm.