PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham HUMAN ANATOMY fifth edition MARIEB | MALLATT | WILHELM 11 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscles of the Body PART 1

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscles of the Body  Skeletal muscles  Produce movements  Blinking of eye, standing on tiptoe, swallowing food, etc.  General principles of leverage  Muscles act with or against each other  Criteria used in naming muscles

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  Movement of skeletal muscles involves leverage  Lever – a rigid bar that moves  Fulcrum – a fixed point  Effort – applied force  Load – resistance

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems Figure 11.1a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems Figure 11.1b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  Bones – act as levers  Joints – act as fulcrums  Muscle contraction – provides effort  Applies force where muscle attaches to bone  Load – bone, overlying tissue, and anything lifted

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  Levers allow a given effort to  Move a heavier load  Move a load farther  Mechanical advantage  Moves a large load over small distances  Mechanical disadvantage  Allows a load to be moved over a large distance

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  First-class lever  Effort applied at one end  Load is at the opposite end  Fulcrum is located between load and effort

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  Examples – seesaws, scissors, and lifting your head off your chest Figure 11.2a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  Second-class lever  Effort applied at one end  Fulcrum is at the opposite end  Load is between the effort and fulcrum  Examples – wheelbarrow or standing on tiptoe  An uncommon type of lever in the body  Work at a mechanical advantage

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships Figure 11.2b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  Third-class lever  Effort is applied between the load and the fulcrum  Work speedily  Always at a mechanical disadvantage Figure 11.2c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Lever Systems: Bone-Muscle Relationships  Most skeletal muscles are third-class levers  Example – biceps brachii  Fulcrum – the elbow joint  Force – exerted on the proximal region of the radius  Load – the distal part of the forearm

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings 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 Organization Scheme Based on Embryonic Development  Overview based upon  Embryonic origin  General function  Muscles develop from mesoderm  Myotomes  Somitomeres  The first seven myotomes of the head  Splanchnic mesoderm

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Development and Basic Organization of the Muscles Figure 11.4a, b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Organization Scheme Based on Embryonic Development  Muscles organized into four groups  Musculature of the visceral organs  Pharyngeal arch muscles  Axial muscles  Limb muscles

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Organization Scheme Based on Embryonic Development  Musculature of the visceral organs  Includes – smooth and cardiac muscle  Develops from splanchnic mesoderm  Pharyngeal arch muscles  Includes  Skeletal muscles of the pharynx  Muscles of the head and neck  Develop from the fourth to seventh somitomeres

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Pharyngeal Arch Muscles Figure 11.4c

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings 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 Axial Muscles  Develop from myotomes and some somitomeres  Dorsal regions of myotomes – deep muscles of the back  Ventral regions of myotomes – muscles of the trunk and neck  Respiratory muscles  Anterior abdominal wall muscles  Muscles of the pelvic floor

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Axial Muscles Figure 11.4d

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Limb Muscles  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 Muscle Compartments of Arm and Forearm  The upper limb has anterior and posterior compartments  Anterior arm compartment muscles  Flex the shoulder or arm  Innervation is the musculocutaneous nerve  Anterior forearm compartment muscles  Flex the wrist and digits  Innervation is the median or ulnar nerve

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Compartments of the Arm and Forearm Figure 11.5a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Compartments of the Arm and Forearm Figure 11.5b

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Compartments of the Thigh  Posterior compartment muscles  Extend the hip and flex the knee  Innervation is the tibial branch of the sciatic nerve  Anterior compartment muscles  Flex the hip and extend the knee  Innervation is the femoral nerve  Medial compartment  Adduct the thigh  Innervation is the obturator nerve

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Compartments of the Leg  Posterior compartment muscles  Contains digital and plantar flexors  Innervation is the tibial nerve  Anterior compartment muscles  Contains digital extensors and dorsiflexors  Innervation is the deep fibular nerve  Lateral compartment muscles  Plantar flex and evert the foot  Innervation is the superficial fibular nerve

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Compartments of the Thigh and Leg Figure 11.6a

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Compartments of the Thigh and Leg Figure 11.6b

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