Arrangement of Fascicles in Muscles Skeletal muscles – consist of fascicles Fascicles – arranged in different patterns Fascicle arrangement – tells about action of a muscle Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Arrangement of Fascicles in Muscles Types of fascicle arrangement Parallel – fascicles run parallel to the long axis of the muscle Strap-like – sternocleidomastoid Fusiform – biceps brachii Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Arrangement of Fascicles in Muscles Types of fascicle arrangement Convergent Origin of the muscle is broad Fascicles converge toward the tendon of insertion Example – pectoralis major Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Arrangement of Fascicles in Muscles Types of fascicle arrangement Pennate Unipennate – fascicles insert into one side of the tendon Bipennate – fascicles insert into the tendon from both sides Multipennate – fascicles insert into one large tendon from all sides Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Arrangement of Fascicles in Muscles Circular Fascicles are arranged in concentric rings Surround external body openings Sphincter – general name for a circular muscle Examples Orbicularis oris and orbicularis oculi Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Arrangement of Fascicles in Muscles Figure 11.3 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Lie anterior and posterior to the body axis Muscles of the Axial Muscles Lie anterior and posterior to the body axis Muscles of the Thorax, abdomen, and pelvis Many muscles of the Neck and some of the head Function to move the trunk and maintain posture Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Limb muscles arise from lateral parts of nearby myotomes Extensors Muscle mass dorsal to limb bones Flexors Muscle mass ventral to limb bones Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Limb Muscles Figure 11.4e Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Interactions of Skeletal Muscles in the Body A muscle cannot reverse the movement it produces Another muscle must undo the action Muscles with opposite actions lie on opposite sides of a joint Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Muscles Classified into Several Functional Groups Prime mover (agonist) Has major responsibility for a certain movement Antagonist Opposes or reverses a movement Synergist – helps the prime mover By adding extra force By reducing undesirable movements Fixator A type of synergist that holds a bone firmly in place Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Compartments of the Limbs Dense fibrous connective tissue divides limb muscles into compartments Muscles in opposing compartments are Agonist and antagonist pairs Each compartment is innervated by a single nerve Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Naming the Skeletal Muscles Location Example – the brachialis is located on the arm Shape Example – the deltoid is triangular Relative size Maximus, minimus, and longus indicate size Example – gluteus maximus and gluteus minimus Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Naming the Skeletal Muscles Direction of fascicles and muscle fibers Name tells direction in which fibers run Example – rectus abdominis and transversus abdominis Location of attachments – name reveals point of origin and insertion Example – brachioradialis Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Naming the Skeletal Muscles Number of origins Two, three, or four origins Indicated by the words biceps, triceps, and quadriceps Action The action is part of the muscle’s name Indicates type of muscle movement Flexor, extensor, adductor, or abductor Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings