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Fiber arrangements

Fiber arrangements and muscle shapes

Fiber arrangement affects 1. Muscle's ability to exert F 2. ROM
Greater cross section diameter= Greater F exertion
Longer muscle= Greater ROM
2 major types of fiber arrangements 1. Parallel 2. Pennate
Parallel Muscles Fibers arranged parallel to length of the muscle Produce >ROM
Types of Parallel Muscles Flat Fusiform Strap Radiate Sphincter (Circular)
Flat Ex- Rectus Abdominus, External Oblique Thin and broad, originating from sheet like aponeuroses Forces are spread over a broad muscle
Fusiform Ex- Brachialis, Biceps Brachii Spindle-shaped w/ central belly that taper into tendons on each end F is focused onto small, bony targets
Strap Ex-Sartorius Uniform in diameter F is focused onto small bony targets
Radiate Ex-Pectoralis Major, Trapezius Triangular or Fan-Shaped or Convergent Flat+Fusiform
Sphincter (Circular) Ex- Orbicularis Oris Endless Strap Muscles Surrounds openings and functions to close them upon contraction
Pennate Muscles shorter fibers arranged obliquely to their tendons > Cross sectional diameter...> Power
Types of Pennate Muscles Unipennate Bipennate Multipennate
Unipennate Ex- Biceps Femoris, Extensor Digitorum Longus, Tibialis Posterior Fibers run obliquely from tendon on one side ONLY
Bipennate Ex- rectus femoris, flexor hallicus longus Fibers run obliquely on both sides of a central tendon
Multipennate Ex-Deltoid Several tendons with fibers running diagonally btwn them
Strongest Contraction produced by Bipennate and Multipennate
Created by: jmgibson1