[ZOO301] Chapter 11_Muscles

CHRISTINE MARIE HONG ULBIS 3BIOLOGY-6 MUSCLE TISSUES Striated Muscle Tissue – composed of long, cylindrical, multinucleate muscle fibers, each with transverse bands and longitudinal striae visible with light microscopy - not a cell but a syncytium formed during histogenesis when myoblasts become aligned end to end and unit, contributing nuclei and protoplasm to the elongated syncytium contained within a delicate plasma membrane, the sarcolemma o

Myofibrils – parallel threadlike within the fiber that caused the longitudinal striations in muscle fibers

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Sarcomeres – composes the myofibril - when shortened, myofibrils bulge and thus, the entire muscle shortens and thickens

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Motor End Plate – portion of the sarcolemma with receptors for neurotransmitters - initiates stimuli along the sarcolemma that result in biochemical interactions between the actin and myosin that result in shortening the sarcomeres

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Motor Unit – a functional group of muscle fibers that contract simultaneously - the larger the number of motor units stimulated, the greater will be the effect of the contraction

Cardiac Muscle Tissue – unique variety of striated muscle tissue - regularly depolarizes (myogenic) and conducts impulses through its own system of fibers - autonomic nerves modify the rhythmicity of this myogenic activity - contains myofibrils and filaments of actin and myosin arrayed similarly to those in skeletal muscle fibers Characteristics: 1) Cells are generally uninucleate. 2) Cells are separated by unique boundaries (intercalated disks) 3) It can contract without nervous stimulation. 4) It is innervated by fibers of the autonomic nervous system. o

Intercalated discs – link cytoplasms of adjacent cells, facilitating ion transport and thereby the rapid passage of action potentials

Smooth Muscle Tissue – cells are fusiform, uninucleate, have myofibrils but lack cross striations - unlike striated muscle tissue, it occurs most often in sheets as part of an organ - like cardiac muscle, it is innervated by the autonomic nervous system MAJOR CATEGORIES OF MUSCLES Somatic Muscles – orient the body (soma) of the organism in the external environment - they are striated muscles that are attached to the ligaments, tendons, and bones of the axial skeleton to the appendicular skeleton and to the skeletal components of the lateral and ventral body walls - innervated by spinal nerves, excepting the small number that operates the tetrapod tongue - said to be voluntary if they can be contracted at will - they are derivatives, either ontogenetically or phylogenetically of the myotomes of mesodermal somites - often referred as myotomal or samitic muscles

Visceral Muscles – maintain an appropriate internal milieu - they are smooth muscles of hollow organs, vessels, tubes, and ducts, the intrinsic musculature of the eyeballs, and the erector muscles of feathers and hair - also include the cardiac muscle - derived chiefly from splanchnic mesoderm and are innervated by the autonomic nervous system Branchiomeric Somatic Muscles – belong to the pharyngeal arches and their ontogenic or phylogenetic derivatives from fishes to human beings - they are striated skeletal muscles - myotomal in origin, but they are derived from the most anterior somites and unsegmented paraxial mesoderm in the head o

Somitomeres – individual subdivisions in the paraxial mesoderm, which shows incomplete segmentation - unlike somites of the body, they do not fully segment and lack sclerotome and dermatome components (the derivatives of these missing components are derived from the neural crest in the head) - innervated by cranial nerves - although somatic, they are typically considered separately because they do not directly assist in orienting the body in the external environment

Contrast between Somatic and Visceral Muscles Somatic Muscles Visceral Muscles Striated, skeletal, voluntary Smooth, nonskeletal, involuntary Primitively segmented Unsegmented Myotomal Arise mostly from lateral mesoderm Mostly in body wall and appendages Mostly in splanchnopleure Primarily for orientation in external environment Regulate internal environment Innervated directly by spinal nerves III, IV, VI and XII Innervated by postganglionic fibers of autonomic nervous system

SKELETAL MUSCLES Skeletal Muscles as Organs o Skeletal Muscles – consist of muscular and tendonous portion  Epimysium – “muscle fascia” - tough, glistening fibrous sheath, that surrounds a muscle - consists chiefly of collagenous connective tissue and elastic fibers in small amounts that vary with the muscle 

Perimysium – surrounds the mahor bundles of muscle fibers (fascicles) within the muscle - penetrates the bundles to encapsulate smaller fascicles

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Endomysium – continuation of perimysium - very fine collagenous reticulum that supports the muscular, neural and vascular components of each functional unit - surrounds each individual muscle fiber superficial to the sarcolemma

 Tendons are continuations of the muscle beyond the site where fascicles end.  Collagenous bundles of the perimysium and epimysium continue into and become part of the tendon.  At the attachment of the tendon to the skeleton, the collagenous bundles of the tendon continue into and contribute to the perichondrium or periosteum of the bone to which they are attached.

 Tension produced by muscle contraction is transmitted throughout the entire organ and from one skeletal attachment to another. Twitch and Tonic Muscle Fibers  Twitch Fibers – predominant fiber in mammals with tonic fibers restricted to the extrinsic eye muscles and ear muscles - perform a wide range of functions with the slow twitch fibers paralleling the postural function and low fatigue of the tonic fibers in amphibians and reptiles

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Slow Twitch Fibers – associated with a richer blood supply and large amounts of myoglobin (thus their dark color)

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Fast Twitch Fibers – glycolytic - represent those that are capable of great power in the absence of oxygen during periods of heavy exertion

Androgens – predominant gonadal hormones of males - cause amino acids to be linked together into polypeptides and proteins - produce larger muscles in males in such that muscles is 80% protein Fiber Type Variations within Twitch Fibers

Slow Twitch (Type I of Mammals) Posture or slow repetitive movements

Fast Oxidative (Type IIA of Mammals) Fast

Fast Glycolytic (Type IIB of Mammals) Powerful and fast

Fatigue slowly

Fatigue slowly

Fatigue quickly

Large number of mitochondria

Large number of mitochondria

Few mitochondria

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

ATP formed by phosphorylation

ATP formed by glycolysis – with possible oxygen debt

“Dark” meat of fish and fowl

Bird flight muscles

oxidative

“White” breast of domestic fowl

Origins, Insertions and Muscle Shapes  Anatomic Origin of a Muscle – site of attachment that remains fixed under most functional conditions - the bone on which it originates is not displaced when the muscle contracts Example: When a biceps muscle of the upper arm contracts, the forearm is flexed. The origin of the biceps is therefore somewhere above the elbow.  Insertion of a Muscle – site of attachment that is usually displaced by contraction of the muscle - muscle may cause displacement of the bone of origin instead of the bone of insertion if the former is immobilized by other muscles Example: The geniohyoid muscle, which extends between the hyoid bone and the lower jaw at the chin, either lowers the lower jaw or draws the hyoid forward, depending on which bone is immobilized at the time. o

Aponeuroses – tough, thin, sheetlike expanses of mammalian tendons and ligaments

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Galea Aponeurotica – major component of the mammalian scalp - lying in intimate association with the integument - common tendon of insertion for a number of thin, broad integumentary muscles of the forehead, temporal, and occipital regions

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Raphes – long, seamlike tendons such as the linea alba in the ventral midline of the trunk - muscles inserting on raphes often compress a cavity and the organs within it

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Tendonous Inscriptions – fine nonmetameric and myoseptalike - transverse many straplike muscles or broad muscular sheets, adding

tensile strength to the muscle - prominent in the rectus abdominis of humans and in the broad oblique and transverse muscle sheets of the abdomen of anurans and many amniotes Actions of Skeletal Muscles o Extensors – tend to straighten two segments of a limb or vertebral column at a joint o Flexors – tend to draw one segment toward another o Adductors – draw a part toward the midline o Abductors – cause displacement away from the midline o Tensors – make a part such as the eardrum more taut o Constrictors – compress internal parts  Sphincters – constrictors that make an opening smaller  Dilators – constrictors that make an opening bigger Example: Tongue or Hyoid  Protractors – cause a part to be thrust forward or outward  Retractors – pulls back  Levators – raise a part  Depresors – lowers the part

Example: Plam  Rotators – cause rotation of a part on its axis  Supinators – rotators that turn the palm upward  Pronators – make it prone (turn it downward)

 Frequently, the muscles act in functional groups and also synergistically with other functional groups that have an opposing action.  While one group is contracting, the opposite group must relax simultaneously and at the same rate, otherwise, a stalemate would be the minimum effect.  For both muscle groups to function smoothly, they must be under reflex regulatory control of the cerebellum, which dispatches motor impulses to appropriate muscles on receiving sensory feedback from proprioceptive receptors located in the muscles, in their tendons, and in the bursas and capsules of affected joints. Names and Homologies of Skeletal Muscles  Direction of fibers – oblique, rectus  Location or Position – thoracis, supraspinatus, superficialis  Number of subdivisions – quadriceps, digastric  Shape – deltoid, teres, serratus  Origin or Insertion – xiphihumeralis, stapedius  Action – levator scapulae, risorius  Size – majo, longissimus AXIAL MUSCLES - skeletal muscles of the trunk and tail - extend forward beneath the pharynx as hypobranchial muscles and; in amniotes, as tongue muscles - do not include branchiomeric or appendicular muscles o

Metamerism – increasingly obscured as locomotion by lateral undulation was superceded by locomotion by limbs - segmental because of their embryonic origin:  They arise from segmental mesodermal somites.  Mesenchyme cells from the myotome of each somite stream into the embryonic lateral body wall and migrate ventrad while undergoing repeated cell division.  They cease migrating when they reach the midvental line, where the linea alba develops.

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 These myotomal cells give rise to blastemas for body wall muscles.  Because the somites are metameric, the blastemas are initially metameric.  Blastemal cells, having become myoblasts, unit to form striated muscle fibers, and the body wall muscles.  Blastermal cells, having become myoblasts, unite to form striated muscle fibers, and the body wall muscles commence to take shape. Myosepta – “myocommata” - separate the muscle of one body segment from the next in the myomeres Anurans and Amniotes: It does not form in the abdominal region of anurans and amniotes. Their abdominal musculature consists of broad sheets strengthened by tendonous incriptions. These sheets are innervated by as many spiral nerves as these were somites that contributed to them.

Trunk and Tail Muscles in Fish - consists of myomeres separated by myosepta to which the longitudinally directed muscle fibers attach - first and foremost role is locomotion - typically, there is myomere for each vertebra and a spinal nerve for each myomere o

Horizontal Skeletogenous Septum – a fibrous sheet that divided the myomeres into dorsal and ventral masses (epaxial and hypaxial) - anchored to dorsal ribs when the latter are present and stretches between the vertebral column and the skin along the entire length of the trunk and tail  Myosepta is zigzag when the skin is removed, but deeper within the wall, the myosepta are elaborately folded, the angles of each zigzag being elongated forward or backward to form muscular cones that fit into the cones of adjacent myomeres like stacked dunce caps. The cones become longer toward the tail, and the apices of caudally directed cones near the end of the trunk are often continues as tendonous extensions that insert on caudal vertebrae.

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Oblique Fibers – think sheet that lies superficial to the main hypaxial mass ventrolaterally in many fishes - a thin ribbon of still more superficial fibers parallels the linea alba on each side  Metamerism of the hypaxial muscles of fishes is interrupted where the pectoral and pelvic girdles are built into the body wall and by the gills.  Dorsal to the gill, the epaxial muscles continue to the skull as epibranchial muscles.  Beneath the gills, the hypaxials extend to the lower jaw as hypobranchial muscles.

Trunk and Tail Muscles of Tetrapods - retained the primitive metamerism of epaxial and hypaxial muscles - metameric axial musculature unaccompanied by a well-developed appendicular musculature is illsuited for locomotion on land - disappearance of epaxial myosepta in amniotes gave rise to long, straplike or pinnate bundles disposed above the transverse processes, leaving only a vestige of metamerism in the deepest bundles Expaxial Muscles of the Trunk - extend from the base of the skull into the tail for varying distance - collectively function in straightening (extending) the vertebral column and in lateral flexion of the body Amphibians (except anurans):

The epaxials retain their primitive metamerism, arising and inserting on myosepta and transverse processes, constituting collectively the dorsalis trunci. Amniotes (except rhynchocephalians): Most epaxials are long bundles, some of which extend over many body segments.

- divided into four groups: 1) Intervertebrals – deepest epaxial muscles and the only ones that to retain their primitive metamerism - extend between two successive transver processes (intertransversarii), two neural spines (interspinales), two neural arches (interarcuales), or two successive zygapophyses (interarticulares) - participate with longer epaxials in maintaining a vertebral posture appropriate to the need of the momments 2) Longissimus – occupy the lateral position above the transverse processes - named because it is the longest epaxial mass - consists of bundles that, with their tendons, may extend over body segments  Capitis bundles – insert on the skull and assist in movements of the head  Cervicis bundles – in the neck  Dorsi bundles – in the trunk Mammals: Longissimus is the dominant extensor. Lateral undulation is minimal. Plays a vitually no role in generalized mammalian locomotion. In the lumbar region, it consists of three district bundles. Medial bundle continues into tail. 3) Spinales – occupy the medial position above the transverse processes - include long and medial bundles that connect neural spines or transverse processes with neural spines several or many segments cephalad and transversospinales that connect transverse processes with the neural spines of the second vertebra forward - often grouped with lumbar intervertebrals; collectively called multifidus spinae Mammals: Their chief role is to assist in maintaining stability (temporary rigidity) of the column in whatever degree of extension or other vertebral muscles impose flexion. Humans: Spinales consist other bundles in maintaining upright posture while standing. 4) Iliocostales – lateral to the longissimus - constitute a thin sheet arising o the ilium and passing forward to insert on the ribs and uncinate processes Reptiles: They are the dominant epaxials because their lateral location their insertions along the length of the column provide leverage for lateral undulation. Crocoldiles: Lateral undulation rotates the pectoral girdle on a vertical axis, thereby increasing the length of the stride of both pairs of limbs. It continues forward into the neck but not caudad into the tail.  In turtles and birds, epaxials are prominent only in the neck because the vertebral column, and in turtles, the ribs are immobilized by fusion with the synsacrum or carapace.  One of the epaxials of birds, complexus, inserts on the interparietal bone and provides power for cracking the eggshell with the beak during hatching.

 Epaxial muscles became increasingly hidden by the expansion dorsad of the appendicular muscles and associated lumbodorsal aponeuroses as a derived condition in amniotes. Hypaxial Muscles of the Trunk 1) Subvertebrals – longitudinal bundles beneath the transverse processes in the roof of the coelom 2) Oblique Sheets 3) Transverse Sheets – located in the lateral body wall (parietal muscles) 4) Rectus Abdominis Muscles – longitudinal straplike muscles on either side of the linea alba Subvertebral Muscles - form a longitudinal band of fairly powerful flexors of the vertebral column lying beneath the transverse processes from the atlas to the pelvis Birds: The portion in the neck is known as longus colli. Subvertebrals are meager in the thorax but become prominent again in the lumbar region where they are represented by the quadratus lumborum. Mammals: The portion of the neck is also called longus colli. Subvertebrals are meager in the thorax but become prominent again in the lumbar region where they are represented by quadratus lumborum and the psoas minor.  Quadratus Lumborum – originates on the centra of several of the last thoracic vertebrae - bases of their ribs on the transverse processes of the lumbar vertebrae - inserts on the ventral angle of the wing of the ilium, with variations depending on the species.  Psoas Minor – commercially known as “tenderloin” - connects the lumbar vertebrae with the pelvic girdle Representative Somatic (Myotomal) Muscles of Head, Trunk, and Forelimbs of Mammals Head and neck

Pharynx

Trunk

Eyeball Superior oblique Inferior oblique Medial rectus Lateral rectus Superior rectus Inferior rectus Branchiomeric Muscles Mandibular muscles Hyoid muscles Other branchial muscles Epaxial Muscles Intervertebrals Intertransversarii Interspinales Interarcuales Interarticulares Longissimus L. capitis L. cervicis L. dorsi Extensor caudae lateralis Spinales S. dorsi S. cervicis S. capitis Transversospinales Iliocostales

Tongue Genioglossus Hyoglossus Styloglossus Lingualis

Hypobranchial Geniohyoideus Sternohyoideus Sternothyroideus Thyrohyoideus Omohyoideus

Hypaxial Muscles Subvertebrals Longus colli Quadratus lumborum Psoas minor Oblique group (parietals) Internal and external intercostals Internal and external obliques of abdomen Cremaster Supracostals Scalenus Serratus dorsalis Levatores costarum Transversus costarum Diaphragm Transverse group (parietals) Transversus thoracis (subcostal) Transversus abdominis Rectus muscles

Forelimb

Extrinsic Secondary appendicular Levator scapulae Rhomboideus Serratus ventralis Primary appendicular Latissimus dorsi Pectoralis

Rectus abdominis Pyramidialis Intrinsic See table - (Chief Intrinsic Muscles of the Pectioral Girdle and Forelimbs of Mammals | Homolgues in Reptiles)

Oblique and Transverse Muscles - along with the rectus muscles, it supports the abdominal viscera in a muscular sling and they compress the viscera for such functions as egg laying, delivery of mammalian young and emptying of the digestive tract - play a major role in external respiration in most amniotes (intercostal) Aquatic Urodeles: External oblique muscle is split into superficial and deep parts. Crocodilians and some Lizards: All three layers consist of two sheets each. Anurans: Internal oblique is sometimes missing. o o

Birds: All sheets are thin. Turtles: They are less than thin (vestigial) Mammals: Muscle slips from the inferior border of the internal oblique. Cremaster muscle forms from the transverse abdominal muscle.

Cremaster Muscle – loops around the spermatic cord commencing at the inguinal ring and inserts on a fibrous sheath in the wall of the scroyum below the testes Supracoastal Muscles – divisions that assist the intercoastals in differentiating the surface of the rib cage (scalenus, serratus dorsalis, levatores costarum, transversus costarum)

Rectus Muscles of the Abdomen - extends longitudinally on either side of the linea alba between the pubic symphysis and the sternum - assists in flexing the trunk and in supporting the abdominal viscera in a muscular sling Urodeles: It is extremely segmental.

Anurans and Amniotes: It exhibits irregular transverse tendonous inscription.

 A pyramidalis muscle in the ventral wall of the marsupial pouch is a slip of the rectus abdominis.  Eutherian mammals may have vestiges of the pyramidalis as a species characteristic or as an anomaly.

Mammalian Diaphragm o Central tendon – constitutes the diaphragm with a pair of semilunar extensions and a muscular portion  Muscular Portion – converges on the tendonous portion from a circumferential perimeter, arising on the xiphoid process ventrally (sternal portion), on the caudalmost ribs or their coastal cartilages laterally (costal portion), and from several lumbar vertebrae dorsally (vertebral portion) Muscles of the Tail – continuation of the epaxial and hypaxial musculature of the trunk o

Extensor Caudae Lateralis – tail section of the longissimus - arises from sacral and caudal vertebrae - inserts on distal tail vertebrae by many long slender tendons - extend the tail and arch it upward

Caudofemoralis – constitutes the fleshy part of the tail (in urodeles and reptiles) - connects several caudal vertebrae at the base of the tail with the femur, being secondarily an extrinsic appendicular muscle - exerts a powerful backward pull on he hind limb and during locomotion of lizards and crocodilians Hypobranchial and Tongue Muscles - derived from the anteriormost trunk somites - supplied by cervical spinal nerves, or with respect to the tongue muscles, by the last cranial nerve (hypoglossal), a cervical spinal nerve that became trapped within the amniote skull o

Fishes: Hypobranchial muscles extend forward from the coracoid region of the pectoral girdle (via coracoarcuales), to insert on Meckel’s cartilages (coracomandibularis), basihyals (coracohyoideus), and the ventralmost segments of the gill cartilages (coracobranchials). They assist the branchiomeric muscles in respiration and feeding movements by expanding the pharynx and gill pouches, moving parts of the hyoid skeleton, and depressing the lower jaw. Amniotes:  Hypobranchial muscles became longer and straplike. They stabilize the hyoid apparatus and larynx and draw these cephalad or caudad, depending on the concurrent actions of other muscles inserting on these same structures.  Tongue is essentially a mucosal sac anchored to the hyoid skeleton and stuffed with hypobranchial muscles.  The chief extrinsic tongue muscles of mammals are the hyoglossus, styloglossus, and genioglossus. APPENDICULAR MUSCLES - those that insert on the girldes, fins, or limbs Fishes

 Paired fins arise in embryos as fin folds that protrude from the lateral body wall. Thereafter, hollow muscle buds sprout from the lower edges of a series of embryonic myomeres near the base of each fin fold.  The buds split into dorsal and ventral moieties, invade the developing fin, and establish blastemas from which dorsal and ventral muscle masses are formed.  Dorsal blastemas form extensors (elevators) of the fin; ventral blastemas form flexors (depressors).  The resulting musculature establishes attachments to the girdles, basalia, radialia and the fascia overlying the base of the fin rays. Tetrapods  The appendicular muscles of tetrapods are far more complex than those of dishes because of the joints in tetrapod limbs. Extrinsic Muscles of the Pectoral Girdle and Forelimbs Dorsal Group o

Latissimus Dorsi – most constant dorsal extrinsic appendicular muscle of tetrapods - inserts on the humeros Urodeles: It is a delicate triangular muscle arising from the superficial fascia that overlies the epaxial myomeres of the shoulder region. Reptiles: It spread dorsad to acquire a firm attachment to the tough fascia that is anchored to neural spines, and it broadened its axial origins by spreading still father caudad. Mammals: It rises from the neural spines of most of the thoracic vertebrae caudal to the first few, and from the tough fibrous lumbodorsal fascia that overlies the lumbar vertebrae and extends all the way to the base of the tail,  Three Extrinsic Muscles That Insert on a Scapula:  Levator Scapulae Ventralis – origin on the transverse processes of the atlas or on the basioccipital bone  Levator Scapulae Dorsalis – origin on the transverse processes of the number of posterior cervical vertebrae  Rhomboideus group – arises from the occiput and neural spines of a series of cervical and anterior thoracic vertebrae

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Serratus Ventralis – arises by many separate prominent tendonous slips from a series of ribs near their junction with the costal cartilages Trapezius – superficial muscle of the shoulder region - survivor of the cucullaris muscle of fishes - acquired attachments to the pectoral girdle and then underwent the same expansion as the latissimus dorsi - eventually became subdivided into several components including cleidotrapezius (cleidocervical), acromiotrapezius (cervical trapezius), and spinotrapezius (thoracic trapezius) - receives its motor innervationvia banchiomeric nerves

Ventral Group  The ventral extrinsic muscles of the forelimb, is subsumed under the general term, “perctoral muscles”.  These fan-shaped muscles, originating primitively on the coracoid cartilages or bones and associated midventral raphe, extended their origins to include the epicoracoid, the entire length of the midventral raphe of the neck.

 They are subdivided into a varying number of superficial and deep muscle masses that converge to insert on the proximal end of the humerus.  Two pectoral muscle masses, the pectoralis and supracoracoideus are seen in their primitive state in a urodele.  Pectoralis – chief adductor  Supracoracoideus – underlies the procoracoid bone - able to elevate the wing because its tendon of insertion passes to the dorsal surface of the humerus Intrinsic Muscles of the Pectoral Girdle and Forelimbs Dorsal Group  Five Postaxial Muscles That Arises from the Scapula  Deltoideus  Teres Major  Teres Minor  Subscapularis  Long Head of the Triceps Branchii – has two additional heads that arise on the humerus - inserts on the olecranon process of the ulna where it exerts a powerful pull that extends the forearm o

Supinators of the Manus (2) – connect the humerus with the radius

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Extensors of the Hand and Digits – with long distal tendons - insert on the skeleton of the wrist and digits - shortest ones are intrinsic to the manus

 The mammalian deltoid muscle is probably homologue of the dorsalis scapulae or scapular deltoid in other tetrapods.  The teres major appears to be a slip of the latissimus dorsi and the teres minor is probably the muscle that, in reptiles, is called scapulohumeralis anterior.  The mammalia subscapular is an expansion of a muscle in the same location in reptiles. Ventral Group  Muscles on the Lateral Aspect of the Scapula:  Supraspinatus  Infraspinatus  The supraspinatus and infraspinatus are homologues of the supacoracoid of reptiles, a broad muscle having a ventral anatomic origin over a broad area of the procoracoid bone near the glenoid fossa.  The coracobranchialis of mammals originates on the coracoid process of the scapula, the latter being the sole mammalian remnant of the coracoid bones of reptiles.  A biceps branchii and a branchialis are the major flexors of the forearm of reptiles and mammals.  A small deep anconeus (not homologus with the anconeus of frogs) extends between the distal end of the humerus and the proximal end of the ulna and a small transverse epitrochleoanconeus partially encirckes the elbow joint medially. Distal to these, pronators of the manus insert on the radius and rotate this bone, and flexors of the manus with origins chiefly on the humerus insert by long tendons on the carpals, metacarpals, and phalanges. Intrinsic to the manus are very short flexors of the digits.  Present in some mammals is a cleidobranhialis that extends from the clavicle to the humerus or ulna. Chief Intrinsic Muscles of the Pectioral Girdle and Forelimbs of Mammals | Homolgues in Reptiles Mammals Muscles of Girdle

Deltoideus

Reptiles Deltoideus clavicularis

Girdle to humerus, proximally

Muscles of Upper Arm Girdle of humerus to proximal end of radius or ulna Muscles of Forearm Humerus and proximal end of radius and ulna to hand Muscles of Hand

Dorsalis scapulae Subscapularis

Subcoracoscapularis

Teres minor

Scapulohumeralis anterior

Supraspinatus Infraspinatus

Supracoracoideus

Coracobrachialis

Coracobrachialis

Teres major Triceps branchii Biceps branchii Branchialis Epitrocheleoanconeus Anconeus

Slip of Latissimus dorsi Triceps branchii Biceps branchii Branchialis Epitrocheleoanconeus Anconeus

Extensors and flexors of carpus and digits Supinators and pronators of hand Extensors, flexors, abductors, adductors of digits

Muscles of the Pelvic Girdle and Hind Limbs Amniotes: Pelvic girldles are incapable of independent mobility. They are united with the vertebral column dorsally, and the two halves meet in a symphysis ventrally. Birds: Pelvic girdle is united with the immobile synsacrum. o

Caudofemoralis Muscle – extends between some of the proximal caudal vertebrae and the femur (urodeles and reptiles) - exerts its pull on the tail - not locomotor in urodeles

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Iliopsoas – the puboischiofemoralis internus of reptiles - appears as a separate iliacus and psoas major muscles (humans and mammals)  The iliac portion arises on the ilium.  The psoas major portion arises from an extensive area of fascia covering the psoas minor and from a series of lumbar vertebrae.  The two portions unite and insert by a powerful tendon on the lesser trochanter, a protuberance on the femur near its head. The muscle protracts and rotates the femur.  Three Hip Muscles:  Gluteus – the reptilian iliofemoralis - most powerful - abducts the thigh and, like the ilipsoas, rotates the femur to turn the foot outward  Pyriformis – thre reptilian caudofemoralis brevis  Gemelli – has a wide origin on sacral and caudal vertebrae and on the ilium and ischium, and inserts a large protuberance, the greater trochanter, near the head of the femur

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Quadratus Femoris – arises on the ilium and the greater and lesser trochanters of the femur and inserts on the ligament in which the patella is embedded

- consists of four muscles (three vasti and a rectus femoris)  Vasti – extend the leg  Rectus Femoris – adducts the thigh, rotating it to carry the foot forward  Other extensors or adductor of the thigh include the semi-membranosus, adductor femoris, adductor longus, pectneus, sartorius, and gracilis. They arise on the ilium, ischium, or pubis, and insert on the shaft of the femur or on the patellar ligament and tibia.  The sartorius, the longest muscle in the human body, is a muscular strap that arises on the ilium and passes diagonally down the medial aspect of the thigh. o

Obturator Muscles (2) – they flex, rotate and abduct the thigh - they arise from the lip of the obturator foramen and from the ischium and pubis - inserted on the proximal end of the femur  A biceps femoris and a semitendinosus are primarily flexors of the leg, although the former also abducts the thigh and the latter extends it. They arise on the ischium and insert on the patella or tibia. Innervation of Somatic Muscles

Exaxials of trunk and tail Appendiculars of epaxial derivation

Dorsal rami of spinal nerves

Hypaxials of trunk and tail Appecndiculars of hypaxial derivation Hypobranchials Mammalian diaphragm

Ventral rami of spinal nerves

Tongue

Cranial nerve 12

SIMITOMERIC AND SOMITIC MUSCLES OF THE HEAD Brachiomeric Muscles  The mesenchyme that provides the stem cells for these muscles come from somitomeres and anterior somites of the head  Their motor neurons lie within a distinct motor column in the central nervous system Fishes: They perform two primitive visceral functions inherited from their filter-feeding ancestors (food handling within the oropharyngeal cavity and respiration) Shark: They operate the jaws and gill arches. Tetrapods: They still operate the jaws. However, with the loss of the gills, the muscles of the former gill arches have acquired new dunctions for life on land. Muscles of the Mandibular Arch o Levator Palatoquadrati – arises on the otic capsule and inserts on the quadrate end of the upper

jaw cartilage - raises the upper jaw o

Adductor Mandibulae – arises on the quadrate process and inserts on Meckel’s cartilage - raises the lower jaw, thereby closing the mouth during the phase of the respiratory cycle when the spiracle is closed and water is being forced over the gills by constriction of the walls of the orobranchial chamber (in Squalus) - enables sharks to hold in a viselike grip any prey unlucky enough to be caught - most powerful muscle of the first arch in all gnathostomes Mammals: Masseter – zygomatic arch Temporalis – temporal bone - inserts on the coronoid process of the ramus of the mandible Pterygoideus – pterygoid fossa  The three muscles on each side constitute a muscular sling for the lower jaw and provide most of the multidirectional tensile forces that produce the side-to-side, upand-down, forward and back, and rotary chewing movements of such different mammals as herbivores, carnivores, and rodents.

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Intermandibularis – extends between Meckel’s cartilage and a strong midventral raphe in the pharyngeal floor - central constrictor that elevates the anterior pharyngeal floor during respiration and feeding Fishes: Their intermandibular muscle is the homologue of the mylohyoideus of tetrapods.  One slip probably gave rise to the digastricus muscle of tetropods (anterior belly, when there are two bellies).  A slip of the first arch muscle that was attached to the articular bone of therapsids remained attached when the bone became the malleus. That muscle became the tensor tympani which tenses the mammalian eardrum.

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Spiracularis – “craniomaxillaris” - slender and inserted on the upper jaw to complete the first arch muscles of Squalus

Muscles of the Hyoid Arch  Levator Hyomandibulae and dorsal contrictor arise on the neurocranium and insert on the hyomandibula and ceratohyal cartilage. Tetrapods:  Branchiohyoideus Muscle – arises in the ceratohyal cartilage and inserts on the epibranchial cartilage of the first gill (in Necturus) - along with levators, it waves the gills back and forth in the water for respiration  Depresor Mandibulae – opens the mouth of the urodeles and many reptiles  Posterior belly of the Digastricus – participates in chewing movements (in some mammals)  Stylohyoideus – anterior belly when there are two; connects the styloid or jugular process of the skull with the anterior horn or body of the hyoid in mammals o

Sphicter Colli – think and overlying the origin of the branchiohyoideus - adheres the skin of the neck of lower tetrapods Reptiles:

It spreads upward around the rear of the skull to insert on the skin of the head and is called platysma. Mammals: Platysma spreads forward onto the dace to become the muscles of facial expression, or facial (mimetic) muscles. Fishes: Sphincter Colli is though to be derived from a portion of the interhyoideus. o

Stapedius Muscle – originates on the posterior wall of the middle ear cavity of mammals and inserts on the stapes, a homologue of the hyomandibular cantilages. - contracts to impede extra loud airborne sounds that might injure the cochlea

Muscles of the Third and Successive Pharyngeal Arches  The muscles of the arches of fishes caudal to the hyoid are constrictors (dorsal and ventral), levators, adductors, and dorsal and lateral interarcuals, which compress or expand the pharyngeal cavity and gill pouches during respiration. 

Contrictors - they lie just under the skin, covered by tough subcutaneous fascia that is not readily removed, and they attach to strong fascia above and below the gill pouches - they compress the gill pouches, expelling respiratory water

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Cucullaris – raises the pharyngeal wall assisted by the levator hyomandibulae of the second arch o

Adductors – those deep in the gill arches connect epibranchial and ceratobranchial cartilages and cause the lateral pharyngeal walls to bow outward when the muscles contract, thereby expanding the pharyngeal chamber

 The ceratobranchials in the floor of the pharynx are hypobranchial, not branchiomeric muscles. Bony fishes: Branchiomeric muscles caudal to the hyoid arch are musch reduced as a consequence of the role of the operculum in moving respiratory water across the gills. Tetrapods: Branchiomeric muscles has pretty mush disappeared. Remaining from arch III are a stylopharyngeous muscle that is used in swallowing. Mammals: Remaining from arch III is a posterior belly of the stylohyoideus. Remining from arch IV are the intrinsic muscles of the mammalian larynx cricothyroideus, cricoarytenoideus, and thyroarytenoideus. Chief Branchiomeric Muscles and Their Innervation in Squalus and in Tetrapods Pharyngeal Arch I Mandibular arch

Pharyngeal Skeleton in Squalus Meckel’s cartilage

Chief Branchiomeric Muscles Squalus Tetrapods Intermandibularis Intermandibularis Mylohyoideus (anterior part) Digastricus (anterior part) Adductor mandibulae

II Hyoid arch

Pterygoquadrate cartilage Hyomandibula Ceratohyal Basihyal

Levator palatoquadrati Spiracularis Levator hyomandibulae Dorsal constrictor Interhyoideus

Cranial Nerve Innervation V

Adductor mandibulae Masseter Temporalis Pterygoidei Tensor Tympani Stapedius Stylohyoideus (anterior part) Depressor mandibulae Digastricus (posterior belly)

VII

III

Gill cartilages

IV to VI

Gill cartilages

Constrictors Levators Adductors Interarcuals Constrictors Levators Adductors Intercuals Cucullaris (derived also from dorsal constrictor 3)

Sphincter colli Platysma Mimetics Stylopharyngeus Stylohyoideus (posterior part)

IX

Thyroarytenoideus Cricoarytenoideus Cricothyroideus

X

Trapezius Sternomastoideus Cleidomastoideus Basioclavicularis

Occipitospinal nerves in shark; spinal roots of XI in amniotes

Extrinsic Eyeball Muscles  They are striated, voluntary muscles that arise on the wall of the orbit and insert on the fibrous sclerotic coat of the eyeball.  In elasmobranchs, their embryonic origin is from preotic somitomeres in the embryonic head.  The most cephalic two somitomeres give rise to eyeball muscles are at the level where the third cranial nerve emerges from the midbrain. This nerve innervates four eyeball muscles, the superior, medial, and inferior rectus, and the inferior oblique.  The next more caudal somitomere is at the level where the fourth cranial nerve emerges. This nerve innervates the superior oblique eyeball muscle.  The last preotic somitomere is at the level where the sixth cranial nerve emerges. This nerve innervates the lateral rectus eyeball muscle.  In many amniotes, muscles insert on the upper lids and nictitating membrane.  Reptile – pyramidalis  Reptiles and Mammals – levator palpebrae superioris  Birds – quadratus  Protractors and retractors of the eyeballs of reptiles and depressors of the lower lids, when present are evidently not of similar origin to the eye muscles because they are innervated by the fifth cranial nerve.

Chief Extrinsic Eyeball and Eyelind Muscles and Their Innervation Cranial Nerve Supply III (Oculomotor)

Extrinsic Eyeball Muscle Superior rectus Inferior rectus Medial (internal) rectus Inferior oblique

IV (trochlear)

Superior oblique

VI (abducens)

External (lateral) rectus Retractor bulbi

Eyelid Muscle Levator palpebrae superioris

Pyramidalis of the eye Quadratus of the eye

INTEGUMENTARY MUSCLES  Extrinsic Integumentary Muscles – their development and anatomical origins are away from the dermis - their insertions are along the undersurface of the dermis

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Costocutaneous Muscles – they are hypaxial integumentary muscles used in locomotion in snakes

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Panniculus Cornosus – “cutaneous maximus” - wraps around the entire trunk of some mammals, enabling armadilos to roll into a ball when endangered - forms a sphincter around the entrance to the abdominal pouch of marsupials, and vigorously shakes flies off horses - probably started as superficial slips of the pectoral musculature that became attached to the undersurface of the skin and then spread - poorly developed in monkeys and absent in humans

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Cutaneous Pectoris – sheet of pectoral musculature - maintains its original attachment to the chest wall in anurans

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Patagial Muscles – slips of pectoral muscled inserted on the skin of the wing membranes (in bats)

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Caninus – elevates the part of the upper lip that hides the spearlike canine tooth used by carnivores for ripping flesh

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Auricular Muscles – direct the pinnas of the ears toward faint sounds (nonhuman mammals)

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Facial Muscles – innervated by cranial nerve VII, a branchiomeric nerve

 Intrinsic Integumentary Muscles – develop entirely within the skin, in the dermis o

Arrectores Plamarum & Arrectores Pilorum – inserted on feather or hair follicles and ruffle the feathers or elevate the fur - smooth muscles in nearly all species and are innervated by the sympathetic nervous system

ELECTRIC ORGANS o Electroplax – modified multinucleate muscle fiber embedded in a vascular jellylike extracellular matrix surrounded by connective tissue - nerve ending terminating on each disc induce the discharge o

Torpedo (Electric Ray): An electric organ lies in each pectoral fin near the gills. It is of branchiomeric origin, being supplied by motor fibers of cranial nerves VII and IX. Raja (Skate) & Electophorus (Electric Eel): Electric organs lie in the tail and are modified hypaxial muscles