Muscles-1.pdf - BIO 342 Comparative Vertebrate Anatomy...

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BIO 342Comparative Vertebrate AnatomyLecture Notes 6 - Muscular SystemVertebrate muscles:striated vs. smoothvoluntary vs. involuntaryskeletal vs. non-skeletalSkeletal muscle (left) & Smooth muscle (right)Skeletal muscle= muscles attached to the skeleton that are striated & voluntaryNon-skeletal muscle = muscles not attached to the skeleton; most are smooth &involuntaryVertebrate Muscles:1 - Skeletal, striated, voluntary musclesoaxial§body wall & tail§hypobranchial & tongue§extrinsic eyeball musclesoappendicularobranchiomeric (homologous to the branchial/ pharyngeal muscles fromfishes to mammals, striated muscles, innervated by cranial nerves)ointegumentary2 - Non-skeletal, smooth, chiefly involuntary muscles
omuscles of tubes, vessels, &hollow organsointrinsic eyeball musclesoerectors of feathers & hair3 - Cardiac muscle4 - Electric organsSkeletal muscles have muscular & tendinous portions:Muscle - consists of skeletal muscle cells (which, in turn, consist of myofibrilsand myofilaments)Tendons - extensions of a muscle's tough connective tissue sheath (fascia &epimysium) that anchor a muscle to its origin & insertionoOrigin = site of attachment that is relatively fixedoInsertion = site of attachment that is normally displaced by contractionof the muscle
Used with permission ofJohn W. KimballNames of skeletal muscles are based on:direction of fibers (e.g.,oblique)location or position (e.g.,superficial)number of divisions (e.g.,triceps)shape (e.g.,deltoid)origin and/or insertion (e.g.,iliocostalis)action (e.g.,levator scapulae)size (e.g.,major)or some combination of theseHomologies:Human muscles were named several hundred years ago, & many of thesenames are still used. Based on similarities of origins & insertions, these nameswere subsequently used for the, apparently, corresponding muscles of othervertebrates. However, origins & insertions are not reliable criteria fordetermining homology because natural selection has sometimes favored 'shifts'in muscle position. More reliable criteria for determining homologies are:oembryonic originonerve supply
Source:Axial Muscles:include the skeletal muscles of the trunk & tailextend forward beneath the pharynx as hypobranchial muscles &muscles ofthe tongueare present in orbits asextrinsic eyeball muscles(check slide 27 in this powerpointpresentation)are metameric (most evident in fish and aquatic amphibians where the axialmuscles are used in locomotion; in other tetrapods, metamerism is obscureddue to presence of paired appendages responsible for locomotion on land)are segmental because of their embryonic origin; arise from segmentalmesodermal somites
Source:Axial musculature of an aquatic salamander,Necturus maculosus. The layers of lateral hypaxial musculature are

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