MAMMALS

Muscular systemComparative Vertebrate Anatomy

GROUP 2General Structures and FunctionsComparative Anatomy of Vertebrates

IntroductionAquatic VertebratesAmphibiansReptilesBirdsMammals

FunctionsBody MovementsStabilise the bodyMovers and Levers with the aid of the skeletonsContraction of the visceraHeat productionTypes

6Somatic:Move bone/cartilageVisceral:Control activities of organs, vessels or ductsVoluntary:Under immediate conscious controlInvoluntary:Not under conscious controlRed: Highly vascularised and rich in myoglobinResist fatigueWhite:Low vascularised and low in myoglobinQuicker to fatigueKinds of musculaturecolorlocationNervous system controlTypes of musculatureSmoothCardiacfound lining the walls of blood vessels and visceral organs such as digestive tract and uterus and also found attached to hairs in integumentary systemFound solely in the musculature of the heart wallBranching of cells increase its overall connectivity and the cells are firmly united with each other through the intercalated disc. Cardiac muscles doesnt fatigue readily, which is a desirable trait in the muscles that maintain the circulation of blood.Action of the cardiac muscle fibers shows mixed control such that the myogenic rhythm of heart is maintained by neurogenic control and the entire unit of cardiac muscle acts as syncytium or single function unit

SkeletalClosely associated with the skeleton and are used in locomotion each skeletal muscle fiber is also a syncytium due to the close connection between cellular unitMUSCLE ORGANIZATION Attaches to bones, skin, fascia Striated Voluntary muscles- Axial muscles- Jaw muscles- Extrinsic eyeball muscles- Appendicular musculature- Integumentary muscles

- Attached to hair follicles and skin Non-striated Involuntary muscles Includes muscle of tubes, vessels and hollow organs, intrinsic eyeball muscles, erectors of feathers and hair Forms the wall of the heart Striated Involuntary muscles Myocardium ElectropaxesSkeletalVisceralCardiacEmbryogenesisMesenchyme from which smooth muscle and some viscera develop

Paired Hypomere differentiated into smooth muscle layers of the alimentary tract and its derivative

Paraxial Mesoderm skeletal muscles developMyotomes of epimereLateral mesoderm of hypomere Somatic: body wall musclesSplanchnic: smooth muscle of viscera

11DevelopmentAxial muscles- Cover the trunk and tail regionJaw muscles- Support the gill arches and contributes the tongue.Extrinsic eye muscles- Muscles of the eyeAppendicular musculature- Attached to girdles, fins or limbs.Integumentary muscles- Attached to some parts of the skeleton and inserted on skin.Axial MusculatureInclude the skeletal muscles of the trunk & tail Are segmental because of their embryonic origin; arise from segmental mesodermal somitesMetamerism is most evident in fishes and aquatic amphibians where the axial muscles are used in locomotion Metamerism is obscured in tetrapods due to presence of paired appendages responsible for locomotion on land Myotomes are separated by myosepta which serve as muscle origins & insertionsMyoseptum becomes indistinct in amniotesJaw MusculatureArises from two embryonic sources:Hypobranchial-Contributes to the formation of the tongue.Branchiomeric- Derived from somitomeres of the head and supplied by cranial.

14Extrinsic Eyeball MusclesSix muscles arises form three different somitomeres:

- Superior, inferior and medial rectus (anterior) and inferior oblique muscles arise form the premandibular somitomere (most anterior) supplied by the III cranial nerve

- The superior oblique arises from the mandibular somitomere (middle) supplied by the IV cranial nerve

- The lateral rectus muscle (posterior) arises from both mandibular and hyoidean somitomeres supplied by the VI cranial nerve15

3 Types of Muscle TissueStriated voluntarymuscle tissueskeletal muscleLong cylindrical multinucleated cellsSarcoplasm = Parallel rows with alternating light(I-band) and dark (A-band) forming striationsAttached to skeleton responsible for voluntary movement.

Smooth involuntarymuscle tissuevisceral muscleElongated cells, tapered ends, nucleus (center)Sarcoplasm = clearFound in internal organs which bring about involuntary movement3 Types of Muscle Tissue

Striated involuntarymuscle tissuecardiac muscleLinear, branching bundles of fibers joined end to end by intercalated discFound in walls of heart to bring the involuntary contraction of the organ3 Types of Muscle Tissue

1. Agonist or prime mover principal mover for specific actionex. Deltoid muscle in abduction of arm2. Antagonist opposite movementex. Latissimus dorsi and pectoralis for deltiod muscle3. Synergist stabilize movement of one joint inhibit undesirable movementsex. brachioradialis and brachialis assist the biceps to create the movement and stabilise the elbow joint.4. Fixator fixes position of the limb when movement occursex. Biceps and triceps hold shoulder and elbow in positionTypes of skeletal muscle as to Action

Types of Skeletal muscles as to Specific Function1.Flexor bend a limbExtensor straighten a limb or component parts2. Adductors draw part toward a median lineAbductors draw part away median line or from neighboring part or limb3. Pronators turn or rotate part downwards (axis) Supinators turn or rotate part forward and upward (axis)ex. (both) palm of the hand

4.Elevator or levator raise or lift a partDepressors lower or depress a partex. Lower jaw5.Constrictors draw parts together or compress a spaceex. Pharynx and abdomenDilators widens an opening or space*Sphincters constrictors surrounding an opening.ex. Mouth, pylorus, anusBasis in Naming Skeletal Musclesdirection 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)some combination of these

Muscles of Aquatic Vertebrates25Muscles of Aquatic Vertebrates

AXIAL MUSCULATURE

2 divisions:Epaxial (Upper)Hypaxial (Lower)

(-) Lateral septum(+) Myomeres(+) Myosepta

Each myotome contributes one muscle segment called MYOMERE.

The short fibers of the myomeres are inserted on partitions of connective tissues called MYOSEPTA, which lie between successive myomeres.It has a slender eel-like body, of a uniform leaden or blackish color, and with seven purse-shaped gill openings on each side. The mouth is fitted for sucking rather than biting, and with it they attach themselves to the bodies of fishes and feed on their flesh, which they scrape off with their rasp-like teeth.26Muscles of Aquatic Vertebrates

Muscles of Aquatic Vertebrates

APPENDICULAR MUSCULATURE

(-) Paired appendages(+)Branchial muscles(not prominent)Muscles of Aquatic Vertebrates

The muscles of JAWED FISHES aremore advanced butless complex than TETRAPODS.Muscles of Aquatic Vertebrates

Fishes- associated with feeding and breathing: Coracoarcuals - opens mouthCoracomandibular - opens mouthCoracohyoid - helps in feedingCoracobranchial - helps in swallowing

Tetrapods- associated with the hyoid apparatus & tongueTongue muscles: hyoglossus, styloglossus, genioglossus (also speech & sound production)Geniohyoid: draws hyoid craniallySternohyoid: draws hyoid posteriorlySternothyroid: draws larynx caudallyTongue of amniotes is a 'sac' anchored to hyoid skeleton & filled with hypobranchial muscle AXIAL MUSCULATURE

2 divisions:Epaxial (Upper)Hypaxial (Lower)

(+) Lateral septum(+) Myomeres(+) Myosepta

MYOMERES become more angled (zig-zag shaped) and are molded into interlocking cones.Muscles of Aquatic Vertebrates

MYOMERES become more angled (zig-zag shaped) and are molded into interlocking cones.To extend the action of each myomere over several vertebrae.To assure that muscle fibers can all shorten at equal rates.

32

Muscles of Aquatic VertebratesStrap-like hypobranchial muscles extend from the pectoral girdle to the visceral arches.Serve to open the jaws and pull the gills downward and backward.Evolved from the hypaxial muscles retaining the longitudinal orientation of fibers.Muscles of Aquatic Vertebrates

APPENDICULAR MUSCULATURE(+) Paired appendages (evolved with fins)Muscles of Aquatic Vertebrates

Dorsal mass ofEXTENSOR:Abductors/LevatorsMoving the fins UPWARD or FORWARDA series of levators above the pharynx lift the gill bars.35Ventral mass of FLEXOR:Adductors/DepressorsMoving the fins DOWNWARD or BACKWARDAdductors reduced the internal angles of each visceral arch.

Muscles of Aquatic Vertebrates

36FISHES have 6 extrinsic eye muscles:Muscles of Aquatic Vertebrates

Rectus muscles have their origin close together deep in the posterior part of the orbit.Oblique muscles have their origin deep in the anterior part of the orbit.These muscles are responsible to rotate the eye around the longitudinal and vertical axes of the head.37Specialized MusclesElectric organsIn fishModified hypaxial muscles

Figure 10.17: Electric eel.

Muscles of Aquatic VertebratesElectric organsConsist of electric discs (up to 20,000) which are modified muscle cell with associated nerves & mitochondriaEach disc (electroplax) produces electric signals that propagate through the water. Specialized skin receptors can sense disturbances which are sent up to specialized regions of the brain that compute a "picture" of the fish's environment.

Electric organs Salt water eel can emit up to 50V Fresh water eel can emit up to 500V Functions: communication, orientation with objects in environment, detection of prey, offense & defense, locating prey (electrolocation)

Muscles of AmphibiansAxial musculatureModified from lower aquatic formsMetameric condition = obscureTrunk reduced in volume

URODELE AMPHIBIANSURODELE AMPHIBIANSDo not have epaxial musclesTheir lateral septum is more dorsal in positionMyotomes are primitiveMuscle fibers still course form one myocommata to the next, The entire epaxial mass formed dorsalis trunciMyotomes vertically arrangedIntersegmental bundles

ANURANS AMPHIBIANSDorsalis trunci become differentiated into intertransversarial muscles between the transverse processes and interneural muscles between neural arches

HYPAXIAL MUSCLES OF AMPHIBIANSADULT URODELESVentral trunk muscles Beginning from the outside, there are superficial and deep external oblique (course in posteroventral direction)Internal oblique layer extend in posterodorsal directionTransversus which fibers almost in a vertical position. It lies next to peritoneumSPECIALIZED ANURANSReduced the number of layers in hypaxial trunk musclesRectus abdominis is large muscle extending from sternum to pubisMyocommata have disappeared from the external oblique and transversus but are retained to some extent in the rectus abdominis as tendinous inscriptionsLastly, the amphibians have muscle that move the to tongue this derived from the hypobranchial muscle

Muscles of ReptilesAXIAL MUSCULATUREEpaxial muscles functions to extend or straighten the spine and provide some lateral flexion. lack myosepta and become complexReptiles AXIAL MUSCULATUREHypaxial muscles functions to bend the spine and provides lateral bending.subvertebral grouprectus abdominis grouplateral groupReptiles APPENDICULAR MUSCULATURE

more numerous and diverse than in AMPHIBIANS.Intrinsic muscles- quadrupedal locomotionDorsal extensorVentral flexor muscles

Extrinsic integumentary muscles - inserted on the underside of the dermis.

Forelimbs

-trapezius muscles derived from the branchial musculature-several muscles derived from the axial musculature-most appendicular muscles are derived directly from appendicular muscles of fish ancestors.Hindlimbs-dorsal and ventral muscle groups are again recognized.*caudofemoralis- a prominent flexor of the thigh of Reptiles.

Extrinsic eyeball musclesEyeball can no longer be rotated around its optical axis.*pyramidalis-muscles inserted on the upper lids and nictitating membrane of Reptiles.

REPTILES is thefirst group of vertebratesto have INTEGUMENTARY MUSCLEScapable of moving the skin.Integumentary muscles

Snakes- locomotor apparatus may include separate muscles, the costocutaneous, to move the ventral scutes.

Muscles of BirdsBirds Muscular StructureMost birds have approximately 175 different muscles.The skin muscles help a bird in its flight by adjusting the feathers.Pygostyle(tail muscle)The pectorals, or the breast musclesTrue Flight thin, stringy muscles of the vertebral column

The supracoracoideus works using a pulley like system to lift the wing while the pectorals provide the powerful downstroke.

Muscles of MAMMALSEpaxial Muscle lack myosepta complexHypaxial Muscle same with all tetrapods* subvertebral group located below transverse process ventroflexes the spineAnterior ribs enlarged penetrates external and internal obliques forms the intercostals muscle ventilation of the lungsLateral group of hypaxial muscle:

- Serrratus- Levator scapulae- RhomboideusBranchial muscle*Ancestor adductor mandibulae of lower vertebrates several muscles in mammals(-) depressor mandibulaeDigastric muscle (new muscle)-ventral constrictor of 1st and 2nd arches innervated by 5th and 7th cranial nervesStapedial muscleMuscle of the larynxConstrictor of the throat

AXIALMUSCLESFISHESAMPHIBIANSREPTILESBIRDSMAMMALSEpaxial(Upper)Solid mass; above the lateral septumMuscle masses subdivided and rearranged into longitudinal musclesMuscle masses subdivided and rearranged into longitudinal musclesMuscle masses subdivided and rearranged into longitudinal musclesHypaxial(Lower)Solid mass; below the lateral septum2 outer oblique layers; 1 inner transverse layer; rectus abdominis2 outer oblique layers and 1 inner transverse layer; rectus abdominis2 outer oblique layers and 1 inner transverse layer; rectus abdominisOblique layers are further subdivided, separated by intercostal musclesSeptumTransverse/Lateral septumDorsally positionLinea albaMyotomesPresentPresentAbsentMyoseptaPresentPresentAbsentAbsentFUNCTIONTo produce an undulating motion that propels the fish through the waterMaintenance of posture, head movement, and respirationMaintenance of posture, head movement, and respirationMaintenance of posture, head movement, and respirationMaintenance of posture, head movement, and respirationComparative Anatomy of VertebratesEpaxials (Tetrapods)

Hypaxials (Tetrapods)

Hypaxials (Tetrapods)

Hypaxials (Tetrapods)JAWMUSCLESFISHESAMPHIBIANSREPTILESBIRDSMAMMALSBranchiomericConstrictors and levator musclesAssociated with mandibular, hyoid and pharyngeal archesAssociated with mandibular, hyoid and pharyngeal archesAssociated with mandibular, hyoid and pharyngeal archesHighly modified; mandibular, hyoid and pharyngeal archesFUNCTIONBreathing and feedingContribute to larynx (vocalization) and throatContribute to larynx (vocalization) and throatContribute to larynx (vocalization) and throatControl vocal functions within larynxHypobranchialAttached posteriorly to pectoral skeletonAssociated with pharyngeal archesAssociated with pharyngeal archesAssociated with pharyngeal archesAssociated with pharyngeal archesFUNCTIONServe to open the jaws and pull the gills downward and backwardMovement of the larynx, hyoid apparatus and tongueMovement of the larynx, hyoid apparatus and tongueMovement of the larynx, hyoid apparatus and tongueMovement of the larynx, hyoid apparatus and tongueComparative Anatomy of Vertebrates

Hypobranchial muscles

BRANCHIOMERIC MUSCLES

HYPOBRANCHIAL MUSCLESAPPENDICULARMUSCLESFISHESAMPHIBIANSREPTILESBIRDSMAMMALSAdductor musclesDorsal; flex finsVentral; recoveryVentral; recoveryVentral; recoveryVentral; recoveryAbductor musclesVentral; extend finsDorsal; propulsiveDorsal; propulsiveDorsal; propulsiveDorsal; propulsiveOther characteristicsIntrinsic muscles are limited in number & undifferentiatedMuch more complex than in fishMore numerous & diverse than in amphibiansIntrinsic musculature is reducedSimilar to reptiles but more diverseFUNCTIONBalance and orientationSupport and locomotionSupport and locomotionSupport and locomotionSupport and locomotionComparative Anatomy of VertebratesRecovery Phase- Forward movement and raising of the limb (adduction) Flexing of arm/leg Extension of hand/ footPropulsive Phase- Backward movement of the limb (abduction) Extension of arm/leg Flexion of hand/footThus, the range of movement of fins is much more limited than that of tetrapod limbs.Appendicular musculature is more complex than that of fishes because the limbs function in both support and locomotion.Better support of body & increased mobility of distal segments of the limbs.81Muscles responsible forAmphibiansReptilesMammalsForelimb abductionLatissimus dorsiLatissimus dorsiLatissimus dorsi;TrapeziusHindlimb abductionCaudofemoralisCaudofemoralisCaudofemoralis;Biceps femoralisPropulsive Phase:

INTEGUMANTARYMUSCLESREPTILESBIRDSMAMMALSSpecialized MusclesCosto-cutaneous musclesArrector pilli muscles; patagial musclesArrector pilli muscles;patagial muscles (bats);mimetic musclesFUNCTIONProvide friction for locomotionAid in flight controlInvolved in facial expressionComparative Anatomy of Vertebrates

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