VERTEBRATE MUSCULAR

SYSTEMMrs. Ofelia

Solano Saludar Department of Natural Sciences University of St. La Salle

Bacolod City

HISTOLOGY: striated, cardiac, smooth

FUNCTION: contraction

locomotion: result of muscle action

posture determinant

orientation of body in the environment

heat production

Muscle is a tissue; muscles are organs

EMBRYOGENESIS

Myotomes of epimere

Lateral mesoderm of hypomere

1. Somatic: body wall muscles

2. Splanchnic: smooth muscle of viscera

GROSS FEATURES OF SKELETAL MUSCLEOrigin & insertion; Tendon; Aponeurosis; Fascia, Action

Various wrappings of connective tissues extend beyond the ends of the muscle fibers to connect with the periosteum of the bone: Tendon - cordlike attachment consisting

of extensions of a muscle's tough connective tissue sheath that anchor a muscle to its origin & insertion

Aponeurosis - thin flat sheet o Fascia - thin flat sheets of connective

tissues that wrap and bind adjacent muscle groups

o Raphe - junction of two muscles at a band of connective tissue to form a line of fusion, such as the linea alba

MUSCLE ACTION

1. Agonists- primary action

2. Antagonistic - oppose or resist the action of another muscle

3. Synergistic - work together to produce a common effect

Names of skeletal muscles are based

on: action (e.g., levator

scapulae) 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)

size (e.g., major)

… or some combination of these

STRIATED MUSCLE

Skeletal, voluntary muscles: axial, body wall & tail, hypobranchial & tongue, extrinsic eyeball, appendicular, branchiomeric or branchial muscles

Myofibrils are striated cylinders within syncytial myofibers

HISTOLOGY

SOMATIC MUSCLES VISCERAL MUSCLES

Histo logy

Striated, skeletal, voluntary Smooth, involuntary, includes cardiac muscle

Seg men tation

Primitively segmented (*partially unsegmented: somitomeres)

Unsegmented

Origin

Myotomal/somitic Lateral mesoderm

Loca tion

Body wall & appendages (*branchial region)

Splanchnopleure

Func tion

Primarily for orientation in external environment

Regulate internal environment

Inner vation

Spinal nerves & cranial nerves III, IV, VI & XII (except tongue)

Postganglionic fibers of ANS

MAJOR CATEGORIES OF STRIATED MUSCLES: somatic, visceral, branchiomeric somatic*

TWITCH (RED) TONIC (WHITE)

Contraction Fast to slow contraction

Slow contraction

Slow Mammalian postural muscles

Amphibian & reptilian postural muscles

Fast Most locomotor muscles

Extraocular & ear muscles of mammals

Innervation Single axon Multiple axons

Action potential

All-or-none A temporal summation with a graded contraction

Onset of fatigue

Variably fatigues

Can maintain tension efficiently

STRIATED FIBER CONTRACTILE TYPES

SLOW TWITCHType I of

mammals

FAST OXIDATIVEType IIA of mammals

FAST GLYCOLYTICType IIB of mammals

Posture or slow repetitive movements

Fast Powerful & fast

Fatigues slowly Fatigues slowly Fatigues quickly

Large # of mitochondria

Large # of mitochondria

Few mitochondria

High oxygen storage proteins (myoglobin): “red muscle”

ATP formed by oxidative phosphorylation

ATP formed by glycolysis- with possible oxygen debt

“Dark meat” of fish & fowl

Bird flight muscles

“White breast” of domestic fowl

FIBER TYPE VARIATIONS WITHIN TWITCH FIBERS Muscles are mixtures of different fiber types;

androgens & continued use result in increase in size & strength of muscle

SMOOTH MUSCLE TISSUE Fusiform, uninucleate cells with myofibrils but

without striations; occur in sheets Two general types:

1. Unitary- has myogenic contraction to aid in sustaining the rhythmic movement of the organ

2. Multiunit- has neurogenic contraction, which requires action potentials sent by neurons

Lateral plate mesoderm in origin

Involuntary- innervated by ANS

Muscles of tubes, vessels, & hollow organs; intrinsic eyeball muscles; erectors of feathers & hair

Regulates internal body temperature

CARDIAC MUSCLE TISSUE

Heart muscle

Uninucleate, striated cells separated by intercalated disks

Lateral plate mesoderm in origin

Involuntary, self depolarizes (myogenic); ANS nerves modify its rhythmicity

Include the skeletal muscles of the trunk & tail

Are segmental because of their embryonic origin; arise from segmental mesodermal somites

Metamerism 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 & insertions

Myoseptum becomes indistinct in amniotes

AXIAL MUSCLES

Myotomes become divided by the horizontal skeletogenous septa into:

1. EPAXIALS- above the septum, dorsoflex spine

2. HYPAXIALS- below the septum, ventroflex spine

o present in orbits as extrinsic eyeball muscles

o extend forward beneath the pharynx as hypobranchial muscles & muscles of the tongue

Epaxial Muscles:

Innervated by dorsal rami of spinal nerves

Extend spine & some lateral bending

Extrinsic eye muscles (innervated by cranial nerves)

JAWED FISHES

Hypaxial Muscles:

Innervated by ventral rami of spinal nerves

Ventroflex and lateral bending

Hypobranchial muscles: hypaxial muscles that migrated forward & come to lie on floor of pharynx, pectoral girdle to jaw; function in respiration & feeding, e.g. coracomandibularis

Epaxials are elongated bundles that extend through many body segments located below the

expanded appendicular muscles; required to operate the limbs lie along vertebral column

TETRAPODS

Urodeles & some lizards - epaxials (DORSALIS TRUNCI) are still obviously metameric

Anterior lateral musculature of a urodele (Ambystoma or tiger salamander)

Beginning with fishes, epaxial bundles split into longitudinal systems: long, short & segmented

Short & long bundles both arch & support the vertebral column

Extend from base of the skull to tip of the tail

SHORT BUNDLES: Extend from the 1st vertebrae to the skull

(occipitals) Short segmental muscles (intervertebrals)

include several systems between various parts of the vertebrae & ribs, with each member extending only over one body segment

Connect processes of adjacent vertebrae Tetrapod bundles perform same function as in

fishes (side-to-side movements of vertebral column)

LONG BUNDLES:

Longissimus group- lies on transverse processes of vertebrae; includes the longest epaxial bundles: longissimus dorsi, longissimus cervicis, longissimus capitis

Iliocostalis group- lateral to longissimus & spinalis; arises on ilium & inserts on dorsal ends of ribs or uncinate processes

Spinalis group- lies close to neural arches; connects spinous processes or transverse processes with those several vertebrae anteriorly

Hypaxials:

Muscles of lateral body wall: oblique (external & internal), transverse, & rectus muscles

Muscles that form longitudinal bands in roof of body cavity: subvertebral muscles

Hypaxials of the abdomen have no myosepta & form broad sheets of muscle

OBLIQUE & TRANSVERSE MUSCLES

Early amphibians & reptiles: ribs developed in myosepta along entire length of the trunk;

Urodeles still have myosepta the length of the trunk, but ribs no longer form in all of them

oes, obliquus externus

superficialis

oep, obliquus

externus profundus oi, obliquus internus

ta, transversus abdominis

Modern amniotes: myosepta & ribs are restricted to the thorax, hence abdominal muscles are not obviously segmented

Hypaxials are reduced in volume compared to fishes; support contents of abdomen & assist in respiration

Weakly developed in most fishes but stronger in tetrapods

Support ventral body wall, compresses abdomen, assist epaxials in bending vertebral column

Consists of: rectus abdominis, cervicis, and geniohyoid in front of hyoid apparatus

Diaphragm – unique to mammals for breathing

RECTUS MUSCLES

INTERCOSTALS external & internal

intercostal (respiration in

amniotes)1. External intercostal

muscles

2. Internal intercostal muscles

3. Ribs

4. Intercartilaginous muscles

5. Sternum

6. Subcostal muscles

7. Vertebral column

SUBVERTEBRAL MUSCLES

Underneath & against transverse processes of vertebrae

Includes the psoas &  iliacus in the lumbar region & the longus colli in the neck

Less developed in the thorax; none in the tail

EPAXIAL HYPAXIALIntervertebrals: Intertransversarii, Interspinalis, Interarcuales, InterarticularisLongissimus: L. capitis, L. cervicis, L. dorsi, Extensor caudae lateralisSpinalis: S. dorsi, S. cervicis, S. capitis, TransversospinalisIliocostales

Subvertebralis: Longus colli, Quadratus lumborum, Psoas minor Oblique group (parietals): Internal & External intercostals, Internal & External oblique of abdomen, Cremaster, Supracostals (Scalenus, Serratus dorsalis, Levatores costarum, Transversus costarum) DiaphragmTransverse group (parietals): Transversus costalis (subcostal), Transversus abdominisRectus muscles: Rectus abdominis, Pyramidialis

Muscles of the back:

Longissimus dorsi - extends vertebral column

Iliocostalis - draws ribs together Multifidus spinae - extends vertebral

column Spinalis dorsi - extends vertebral

columnAbdominal muscles:

Rectus abdominis - compresses abdomen

Internal oblique - compresses abdomen

External oblique - constricts abdomen

Internal oblique - constricts abdomenRespiratory muscles:

Serratus - draw ribs cranially Scalenus - flexes the neck Diaphragm - separates the

thoracic/abdominal cavities, functions in breathing

Intercostals - protract/retract ribs

ACTIONS OF SELECTED AXIAL MUSCLES

Arise from preotic somitomeres

6 voluntary muscles

Obliques rotate eye along its transverse axis; rectus move eyes up, down, left, right; retractor in some

Retractor bulbi pulls the eyeball further into the orbit to allow for coverage by the nictitating membrane (lacking in humans)

Innervated by the oculomotor nerve

EYE MUSCLES

Develop from somitomeres & the myotomes caudal to those that produce the ocular muscles

Closely associated with the visceral skeleton so they are used in both breathing and feeding.

Perform the function of operating the jaw, opening and closing the spiracle

Primitively had a levator & a constrictor muscle series; in present vertebrates coracobranchials, subarcuals and ventral transversals are added

May be subdivided based on what visceral arch they are associated with

BRANCHIOMERIC MUSCLES

Muscles of the Mandibular Arch: FISHES - operate the jaws: adductor

mandibulae & intermandibularis (mylohyoid in mammals)

TETRAPODS- muscles of 1st arch still operate jaws; adductors of mandible: masseter & temporalis, pterygoid, anterior belly of digastric, tensor palati & tensor tympani of mammals

Muscles of the Hyoid Arch: Constrictors: interhyoideus (posterior belly of

digastric) & constrictor colli of reptiles & birds (platysma & facial muscles in mammals)

Levators become depressor mandibulae & stapedius

In fishes, muscles become reduced because the operculum plays important role in respiration

Muscles of 3rd & successive arches: Levators: cucullaris of gill-bearing vertebrates

become the trapezius & sternocleidomastoid of tetrapods

Constrictors have no representatives in tetrapods

In tetrapods, primary muscles include: stylopharyngeus (Arch III) - used for swallowing

Remaining arches give rise to intrinsic muscles of the larynx or ‘voicebox’

Hypobranchial- ventral muscles of the head and trunk region that perform functions associated with jaw and tongue movement

Extend forward from pectoral girdle & insert on mandible, hyoid, & gill cartilages

Strengthen floor of pharynx

Assist branchiomeric muscles in elevating floor of mouth, lowering jaw, & extending gill pouches

TONGUE MUSCLES

Fishes- associated with feeding and breathing: Coracoarcuals - opens mouth Coracomandibular - opens mouth Coracohyoid - helps in feeding Coracobranchial - helps in swallowing

Tetrapods- associated with the hyoid apparatus & tongue Tongue muscles: hyoglossus, styloglossus,

genioglossus (also speech & sound production) Geniohyoid: draws hyoid cranially Sternohyoid: draws hyoid posteriorly Sternothyroid: draws larynx caudally

Tongue of amniotes is a 'sac' anchored to hyoid skeleton & filled with

hypobranchial muscle

Hypobranchials ending in "hyoid" stabilize hyoid and larynx; e.g. geniohyoid, sternohyoid, sternothyroid, thyrohyoid

Those beginning or ending with "thyro" are attached to the larynx; e.g. thyrohyoid

Those ending with “glossus” or start with “lingu” are tongue muscles, e.g. lingualis, styloglossus

EYEBALL HYPO BRANCHIAL (tongue)

BRANCHIOMERIC

(pharynx)Superior & inferior obliqueMedial & lateral rectusSuperior & inferior rectus

GenioglossusHyoglossusStyloglossusLingualis

Mandibular musclesHyoid musclesOther branchial muscles

Muscles of girdles and appendages

Move fins or limbs

Innervated by ventral ramus of spinal nerves

Two types based on origin:

o Extrinsic - originate on axial skeleton or fascia or trunk & insert on girdles or limbs

o Intrinsic - originate on girdle or proximal skeletal elements of appendage & insert on more distal elements

APPENDICULAR MUSCLES

FISHES Appendicular

muscles serve mostly as stabilizers

Intrinsic muscles are limited in number and undifferentiated

Originated as extensions of hypaxials of body wall

Paired fins are appendicular (from myotome)

Median dorsal & ventral fins are NOT appendicular, from myotome of epaxials & hypaxials respectively

Dorsal mass on paired fins are extensors or abductors

Ventral mass on paired fins are flexors or adductors

TETRAPODS Appendicular

muscles are much more complicated than in fish

Greater leverage required for locomotion on land

Jointed appendages (as opposed to fins) require complex muscles

INTRINSIC (PRIMARY) APPENDICULAR MUSCLES

Form from blastemas within the limb bud

Amphibians - much more complex than in fish

Reptiles - more numerous & diverse than in amphibians; better support of body & increased mobility of distal segments of the limbs

Mammals - similar to reptiles but more diverse

BIRDS

Intrinsic musculature is reduced

Pectoralis (humerus adductor), is the largest flight muscle that lowers wing

Supracoracoideus elevates wing

Dorsal group of the forelimbs (e.g., trapezius and latissimus dorsi) arise on:

o fascia of trunk in lower tetrapods

o skull, vertebral column, & ribs to a point well behind the scapula in higher tetrapods & converge on the girdle & limb

Ventral group (e.g., pectoralis) arises on sternum & coracoid, & converge on limb

RESULT = pectoral girdle & limb are joined to trunk by extrinsic appendicular muscles

EXTRINSIC APPENDICULAR MUSCLES

The 'muscular sling' of tetrapods: Appendicular muscles of the forelimbs

suspend the anterior body of tetrapods from the

shoulders: axial muscles (rhomboideus & serratus

ventralis) branchial muscles (trapezius) forelimb

musculature (pectoralis)

The pelvic girdle requires no such muscular anchoring because it is attached directly to the vertebral column, resulting to relatively lesser volume of extrinsic muscle in posterior limbs.

Referred to as 20 appendicular muscles because:

they arise from embryonic body wall & spread to the girdles and limb buds

it was not their original function to operate appendages

MAMMALS REPTILES

EXTRINSIC: Forelimb only Secondary appendicular: Levator scapulae, Rhomboideus, Serratus ventralisPrimary appendicular: Latissimus dorsi, Pectorales

Secondary appendicular: Levator scapulae, Rhomboideus, Serratus ventralisPrimary appendicular: Latissimus dorsi, Pectorales

INTRINSIC:

GIRDLE (girdle to humerus, proximally)

DeltoideusSubscapularisTeres minorSupraspinatus InfraspinatusCoracobrachialisTeres major

Deltoideus clavicularisDorsalis scapulaeSubcoracoscapularisScapulohumeralis anteriorSupracortacoideusCoracobrachialisSlip of Latissimus dorsi

UPPER ARM (girdle of humerus to proximal end of radius or ulna)

Triceps brachiiBiceps brachiiBrachialisEpitrochleoanconeusAnconeus

Triceps brachiiBiceps brachiiBrachialisEpitrochleoanconeusAnconeus

FOREARM (humerus & proximal end of radius & ulna to hand)

Extensors & flexors of carpus & digitsSupinators & pronators of hand

Extensors & flexors of carpus & digitsSupinators & pronators of hand

HAND Extensors, flexors, abductors, adductors of digits

Extensors, flexors, abductors, adductors of digits

Region of Body Shark Salamander Mammal

Hypobranchial (pharyngeal) muscles

CoracoarcualesCoracomandibularisCoracohyoid

TongueGeniohyoidRecus cervicis

TongueGeniohyoidSternohyoid, Sternothyroid

Pectoral Appendages

Dorsal extensors        Ventral flexors

Latissimus dorsi Shoulder muscles Arm extensors  PectoralisSupracoracoidArm flexors

Latissimus dorsi, cutaneous maximusDeltoids, subscapularis, teres majorTriceps, supinator (turn hand up), extensors of manus and digitsPectoralisSuprasinatus, infraspinatusBiceps,pronator, flexors of manus and digits

Branchial muscles First ArchAdductor mandibulaeIntermandibularis

Adductor mandibulaeIntermandibularis

Masseter, temporalis, pterygoidsmylohyoid

  Second ArchVentral constrictorsLevator

Subarcual rectus, interhyoid, constrictor colli

platysma

  Other archesTrapezius (cucullaris)

Trapezius Trapezius (and its smaller units), sternomastoid,cleidomastoid

Move skin of amniotes

Extrinsic, striated muscle (e.g., platysma)

Originate on the skeleton & insert on the underside of the dermis

Intrinsic integumentary muscles (arrector pili muscles) lie entirely within the dermis; found in birds & mammals; mostly smooth muscles

INTEGUMENTARY MUSCLES

Consist of electric discs (up to 20,000) which are modified muscle cell with associated nerves & mitochondria

Each 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)