Y khoa, y dược - The muscular system: Part A

10 The Muscular System: Part ASkeletal Muscles: Functional GroupsPrime moversProvide the major force for producing a specific movementAntagonistsOppose or reverse a particular movementSkeletal Muscles: Functional GroupsSynergistsAdd force to a movementReduce undesirable or unnecessary movementFixatorsSynergists that immobilize a bone or muscle’s originNaming Skeletal MusclesLocation—bone or body region associated with the muscleShape—e.g., deltoid muscle (deltoid = triangle) Relative size—e.g., maximus (largest), minimus (smallest), longus (long)Direction of fibers or fascicles—e.g., rectus (fibers run straight), transversus, and oblique (fibers run at angles to an imaginary defined axis)Naming Skeletal MusclesNumber of origins—e.g., biceps (2 origins) and triceps (3 origins)Location of attachments—named according to point of origin or insertion Action—e.g., flexor or extensor, muscles that flex or extend, respectivelyMuscle Mechanics: Arrangement of FasciclesCircularFascicles arranged in concentric rings (e.g., orbicularis oris)ConvergentFascicles converge toward a single tendon insertion (e.g., pectoralis major)Muscle Mechanics: Arrangement of FasciclesParallelFascicles parallel to the long axis of a straplike muscle (e.g., sartorius)FusiformSpindle-shaped muscles with parallel fibers (e.g., biceps brachii)Muscle Mechanics: Arrangement of FasciclesPennateShort fascicles attach obliquely to a central tendon running the length of the muscle (e.g., rectus femoris)Figure 10.1(a)(b)(e)(d)(g)(f)(c)Circular (orbicularis oris)(b) Convergent (pectoralis major)(c) Parallel (sartorius)(d) Unipennate (extensor digitorum longus)(f) Fusiform (biceps brachii)(g) Multipennate (deltoid)(e) Bipennate (rectus femoris)Muscle Mechanics: Lever SystemsComponents of a lever systemLever—rigid bar (bone) that moves on a fixed point or fulcrum (joint)Effort—force (supplied by muscle contraction) applied to a lever to move a resistance (load)Load—resistance (bone + tissues + any added weight) moved by the effort10 x 25 = 1000 x 0.25250 = 250 Effort x length of effort arm = load x length of load arm(force x distance) = (resistance x distance) (a) Mechanical advantage with a power leverLoadEffortFulcrumLoadEffort10kg1000 kgFulcrum25 cm0.25 cmFigure 10.2aFigure 10.2b100 x 25 = 50 x 502500 = 2500 (b) Mechanical disadvantage with a speed leverLoadEffortFulcrumLoadEffort100 kg50 kgFulcrum25 cm50 cmClasses of Lever SystemsFirst classFulcrum between load and effortFigure 10.3a (1 of 2)(a) First-class leverArrangement of the elements isload-fulcrum-effortExample: scissorsLoadFulcrumFulcrumLoadEffortEffortFigure 10.3a (2 of 2)(a) First-class leverArrangement of the elements isload-fulcrum-effortIn the body: A first-class lever systemraises your head off your chest. Theposterior neck muscles provide the effort,the atlanto-occipital joint is the fulcrum,and the weight to be lifted is the facialskeleton.LoadFulcrumEffortClasses of Lever SystemsSecond classLoad between fulcrum and effortFigure 10.3b (1 of 2)(b) Second-class leverArrangement of the elements isfulcrum-load-effortExample: wheelbarrowLoadLoadEffortFulcrumFulcrumEffortFigure 10.3b (2 of 2)(b) Second-class leverArrangement of the elements isfulcrum-load-effortIn the body: Second-class leverage isexerted when you stand on tip-toe. Theeffort is exerted by the calf musclespulling upward on the heel; the joints ofthe ball of the foot are the fulcrum; andthe weight of the body is the load.LoadEffortFulcrumClasses of Lever SystemsThird classEffort applied between fulcrum and loadFigure 10.3c (1 of 2)(c) Third-class leverArrangement of the elements isload-effort-fulcrumExample: tweezers or forcepsFulcrumLoadLoadEffortEffortFulcrumFigure 10.3c (2 of 2)(c) Third-class leverArrangement of the elements isload-effort-fulcrumIn the body: Flexing the forearm by thebiceps brachii muscle exemplifiesthird-class leverage. The effort is exertedon the proximal radius of the forearm, thefulcrum is the elbow joint, and the load isthe hand and distal end of the forearm.LoadEffortFulcrumMajor Skeletal Muscles of the BodyGrouped by function and locationInformation for each muscleName and description—note information in the name Origin and insertion—there is usually a joint between the origin and the insertion Action—insertion moves toward origin; best learned by acting out muscle movement on one’s own bodyInnervation—name of major nerve that supplies the muscleFigure 10.4ShoulderArmForearmPelvis/thighThighLegHeadFacialNeckThoraxAbdomenThighLegTrapeziusDeltoidTriceps brachiiBiceps brachiiBrachialisPronator teresBrachioradialisFlexor carpi radialisPalmaris longusIliopsoasPectineusRectus femorisVastus lateralisVastus medialisFibularis longusExtensor digitorum longusTibialis anteriorTemporalisEpicranius, frontal bellyOrbicularis oculiZygomaticusOrbicularis orisSternohyoidSternocleidomastoidPectoralis majorPectoralis minorSerratus anteriorIntercostalsExternal obliqueRectus abdominisInternal obliqueTransversus abdominisSartoriusTensor fasciae lataeAdductor longusGracilisGastrocnemiusSoleusMasseterPlatysmaFigure 10.5ArmTriceps brachiiBrachialisForearmBrachioradialisExtensor carpiulnaris Extensor digitorumIliotibial tractLegGastrocnemiusSoleusFibularis longusNeckEpicranius, occipital bellySternocleidomastoidTrapeziusShoulderHipGluteus mediusGluteus maximusThighBiceps femorisAdductor magnusSemitendinosusSemimembranosusLatissimus dorsiRhomboid majorInfraspinatusDeltoidTeres majorFlexor carpi ulnarisExtensor carpiradialis longus Calcaneal(Achilles) tendonHamstrings: Muscles of the HeadTwo groupsMuscles of facial expressionMuscles of mastication and tongue movementMuscles of Facial ExpressionInsert into the skinImportant in nonverbal communicationAll innervated by cranial nerve VII (facial nerve)Muscles of Facial ExpressionEpicranius (occipitofrontalis)Bipartite muscle consisting of theFrontalis Occipitalis Galea aponeurotica—cranial aponeurosis connecting above musclesThe two muscles have alternate actions of pulling the scalp forward and backwardFigure 10.6Corrugatorsupercilii Orbicularis oculiLevator labiisuperiorisZygomaticusminor and majorBuccinatorRisoriusOrbicularis orisMentalisDepressorlabii inferiorisDepressor anguli orisPlatysmaGaleaaponeuroticaFrontal bellyOccipitalbellyTemporalisMasseterSternocleidomastoidTrapeziusSplenius capitisEpicraniusMuscles of Mastication and Tongue MovementFour pairs involved in masticationPrime movers of jaw closureTemporalis and masseterGrinding movementsMedial and lateral pterygoids Muscles of Mastication and Tongue MovementAll are innervated by cranial nerve V (trigeminal nerve)Buccinator muscles (of facial expression group) also help by holding food between the teethThree muscles anchor and move the tongueAll are innervated by cranial nerve XII (hypoglossal nerve)Figure 10.7aOrbicularisorisTemporalisMasseterBuccinator(a)Muscles of Mastication and Tongue MovementPLAYA&P Flix™: TemporalisPLAYA&P Flix™: MasseterPLAYA&P Flix™: BuccinatorFigure 10.7bLateralpterygoidMedialpterygoidMasseterpulled away(b)Figure 10.7cTongueStyloid processStyloglossusHyoglossusStylohyoidHyoid boneThyrohyoidGenioglossusMandibularsymphysis GeniohyoidThyroid cartilage(c)Muscles of the Anterior Neck and ThroatMost are involved in swallowingTwo groups Suprahyoid InfrahyoidSuprahyoid Muscles of the Anterior Neck and Throat Four deep muscles are involved in swallowing (they move the hyoid bone and larynx) Form the floor of the oral cavityAnchor the tongueMove the hyoid bone and the larynxInfrahyoid Muscles of the Anterior Neck and Throat Straplike muscles that depress the hyoid and larynx as swallowing ends and during speakingFigure 10.8aMylohyoidAnteriorbellyPosteriorbellyStylohyoid (cut)ThyrohyoidThyroid cartilageof the larynxMedian rapheSternothyroidStylohyoidHyoid boneOmohyoid(superior belly)SternohyoidSternocleido-mastoid Omohyoid(inferior belly)DigastricThyroid gland(a)Figure 10.8cBuccinatorTensor veli palatiniLevator veli palatiniSuperior pharyngealconstrictorMiddle pharyngealconstrictorHyoid boneThyrohyoidmembraneInferiorpharyngealconstrictorEsophagusMandibleMylohyoid(cut)GeniohyoidHyoglossusThyroidcartilageof larynxTracheaStyloid process(c)Infrahyoid Muscles of the Anterior Neck and ThroatPLAYAnimation: Rotatable facePLAYAnimation: Rotatable headMuscles of the Neck and Vertebral ColumnTwo functional groupsMuscles that move the headMuscles that extend the trunk and maintain postureMuscles of the Neck and Vertebral Column: Head MovementSternocleidomastoid—major head flexor Suprahyoid and infrahyoid—synergists to head flexion Sternocleidomastoid and scalenes—lateral head movements Semispinalis capitis—synergist with sternocleidomastoidSplenius (capitis and cervicis portions): head extension, rotation, and lateral bendingFigure 10.9a1st cervicalvertebraSternocleido-mastoid(a) AnteriorBase ofoccipital boneMiddlescaleneAnteriorscalenePosteriorscaleneMastoidprocessFigure 10.9bSpleniuscapitisSpinousprocessesof thevertebraeSpleniuscervicisMastoid process(b) PosteriorMuscles of the Neck and Vertebral Column: Head MovementPLAYA&P Flix™: Semispinalis capitisPLAYA&P Flix™: Splenius capitisMuscles of the Neck and Vertebral Column: Trunk ExtensionDeep (intrinsic) back musclesErector spinae (sacrospinalis) group—prime movers of back extension and lateral bendingIliocostalisLongissimusSpinalis Semispinalis and quadratus lumborum—synergists in extension and rotation Figure 10.9dMastoid processof temporal boneSemispinaliscapitisSemispinaliscervicisMultifidusQuadratuslumborum SemispinalisthoracisLongissimus capitisIliocostalis cervicisLongissimuscervicis Iliocostalisthoracis Longissimus thoracisSpinalis thoracisIliocostalislumborumExternal obliqueIliocostalisLongissimusErectorspinaeSpinalisLigamentumnuchae (d)Muscles of the Neck and Vertebral Column: Trunk ExtensionPLAYA&P Flix™: LongissimusPLAYA&P Flix™: IliocostalisPLAYA&P Flix™: Spinalis