Compa Muscular System

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					Muscular System

   Josefino R. Castillo
   University of Santo Tomas
The muscle tissues
                        Skeletal muscle,
                         striated, voluntary;
                         linear, unbranched

                        Smooth muscle,
                         involuntary; found in
                         digestive tract

                        Cardiac muscle,
                         striated, involuntary;
                         found in the heart;
                         presence of
                         intercalated disk (see

   Origin – the fixed part of a muscle; usually proximal in position
   Insertion – the movable part of a muscle; usually distal in position
   Belly – the part of the muscle with the widest diameter
   Action – the contraction or relaxation of the muscle resulting in any
    of the following:
     Flexor – reduces a joint angle

     Extensor – increases a joint angle

     Adductor – draws a limb toward the central body mass

     Abductor – draws a limb away from the central body

     Levator – raises a part

     Depressor – lowers a part

     Constrictor – reduces an opening

     Dilator – increases an opening
                                   dermatome (dermis of the skin)
                     epimere       sclerotome (skeletal system)
                                   myotome (voluntary muscles)
                     mesomere – (reproductive system)
                     hypomere – (branchial/branchiomeric muscles)

   • The mesoderm divides into three: the dorsal epimere, the lateral
     mesomere, and the ventral hypomere.
   • Soon, each region differentiates into different organs
   • The epimere divides into three: the dermatome that gives rise to
     the dermis of the skin; the sclerotome, that gives rise to the entire
     skeletal system; and the myotomes for the voluntary muscles.
   • The entire reproductive system is derived from the mesomere
   • The branchial/branchiomeric (involuntary) muscles of gills/ gill
     arches in fishes are derived from the hypomere
Groups of Somatic Muscles
Muscle Groups                             Innervation (based on shark)
Axial muscles
 Extrinsic ocular muscles   Oculomotor (III), trochlear (IV), and
                                 abducens (VI) nerves
 Branchiomeric muscles
  Mandibular muscles        Trigeminal (V) nerve
  Hyoid muscles             Facial (VII) nerve
  Branchial muscles         Glossopharyngeal (IX) and vagus (X) nerves
 Epibranchial muscles       Dorsal rami of occipital and anterior
                                spinal nerves
 Hypobranchial muscles      Ventral rami of spino-occipital nerves,
                                 form hypobranchial nerve

 Trunk and tail muscles
 Epaxial muscles            Dorsal rami of spinal nerves
 Hypaxial muscles           Ventral rami of spinal nerves
Appendicular muscles
 Dorsal group               Ventral rami of spinal nerves
 Ventral group              Ventral rami of spinal nerves
Embryonic Development
Embryonic Development
Embryonic Development
Parietal musculature

• The muscle is divided into epaxial muscles (lying above
  the lateral line (horizontal skeletogenous septum) and
  hypaxial (lying below the line)
• Muscles are separated by connective tissue partitions
 Epaxial vs. Hypaxial muscles
• In fishes, the epaxial
  and hypaxial
  muscles are made
  up of longitudinal
  bundles which are
  modified for lateral
• In amphibians, the
  muscles are
  specialized for
 NOTE: Be familiar with the names of the muscles in the diagram
 Epaxial vs. Hypaxial muscles

• In reptiles, the dorsalis trunci is
  split into longissimus dorsi and
  iliocostalis while the
  interspinalis is now called the
• The obliques are now more
• The rectus abdominis lies over
  part of the internal oblique and
  transversus abdominis
Branchial/branchiomeric muscles
Branchial/branchiomeric muscles

   The branchial and/or branchiomeric muscles are found in the gill
    region of fishes and in the head and neck of tetrapods

   In the shark, (see diagram in previous slide) this consists of the
    superficial constrictor above the gill slits, the ventral hyoid
    constrictor, intermandibularis, adductor mandibulae, preorbitalis,
    and other muscles shown in brown

   These muscles are used in opening the mouth or moving water
    into and out of the gill chamber, i.e. respiration and feeding
Branchiomeric and shoulder muscles
Branchiomeric and shoulder muscles

   In the salamander, the same muscles (also shown in brown) are
    attached to the mouth

   This includes adductor mandibulae, depressor mandibulae,
    levatores arcuum, sphinctor colli and the muscles attached to the

   Note the presence of the cucullaris which is also found in sharks

   The shift in habitat from aquatic to terrestrial resulted in a change
    in musculature that should provide dorsoventral movement of the
    head which has to be raised from the ground
Muscles of the head in man

   In man, the head is
    not as muscular as
    it is in lower
   Some superficial
    muscles are found
    in front while the
    back (dorsal) is
    merely covered by
Hypobranchial musculature
Hypobranchial musculature

   The hypobranchial muscles are found below the mandible of fishes
    and in the neck of tetrapods

   In the shark, (see diagram in previous slide) this consists of (from
    the ventral side) coracomandibularis, intermandibularis,
    coracohyoideus and interhyoideus

   In mammals (cat), this includes the derivatives of the rectus cervicis
    namely: the geniohyoid, omohyoid, sternothyroid, thyrohyoid, and
   Other muscles of the neck include the sternomastoid that forms a V-
    shaped structure at the base of the neck, the mylohyoid that runs
    across the floor of the mouth, the digastric, and the stylohyoid
    Dorsal trunk muscles
• The epaxial muscle in amphibians
  are almost undifferentiated,
  collectively called dorsalis trunci
• In mammals (rabbit), the epaxial
  muscle is divided into an
  iliocostalis adjacent to the
  horizontal skeletogenous septum;
  the longissimus dorsi at the
  lumbar region, that extends to the
  head as the longissimus
  capitis; and a multifidus spinae
  in the lumbar region, extending
  anteriorly as the spinalis dorsi in
  the chest region, and as
  semispinalis capitis et cervicis
  into the head and neck
    Trunk muscles

    Pls refer to the
     table towards
     the end of this
     presentation for
     a comparison of
     trunk muscles
Limb muscles
    Limb muscles
   Note: compare the
    muscles shaded
   These muscles
    are generally used
    for walking instead
    of swimming,
    hence a change
    from dorsal or
    ventral fin
    constrictors or
    levators to
    complex flexors
    and extensors is in
Limb muscles
Special Sense Organs

                          Electric organs
                           which are
                           modified from
                           muscles can
                           electricity in
                           these fishes
  Comparative Anatomy of the Vertebrate Muscular System
 Chordate                      Epaxial muscles                                        Hypaxial muscles
Amphioxus    -undifferentiated; myotomes found as V-shaped myotomes separated by connective tissue partitions, the
Fishes       - dorsal longitudinal muscle bundles; with similar     -lateral and ventral longitudinal muscle bundles; no
             partitions as the amphioxus                            rectus abdominis
Amphibians   -modified into dorsalis trunci; longissimus dorsi      -modified into external oblique, and transversus
             found at the back; iliolumbaris, and                   abdominis; rectus abdominis found on either side of
             coccygeoiliacus, coccygeosacralis found                the linea alba, divided into segments by inscriptiones
             posteriorly; separated from hypaxial muscles by        tendinae (tendinous inscriptions)
             horizontal skeletogenous septum
Reptiles     -presence of a transverse spinalis system;             -modified into external oblique, and an internal
             longissimus divided into longissimus capitis going     oblique; rectus abdominis also present as in
             to the head, and a longissimus dorsi proper in         amphibians
             the lumbar region
Birds        -modified for flight, highly reduced as a result of    -well-developed chest muscles adapted for flight
             merging of muscles
Mammals      -multifidus spinae on either side of the middorsal     -presence of an outer external oblique that runs
             line of the lumbar region homologous to transverse     posteroventrally, an internal oblique running
             spinalis system of reptiles; presence of two bundles   anteroventrally, and a transversus abdominis that
             of longissimus dorsi proper and a lateral              runs across the abdomen; the rectus abdominis
             iliocostalis adjacent to the horizontal (or lateral)   continues into the neck as the rectus cervicis and
             skeletogenous septum; anteriorly, the multifidus       differentiates into five muscles: the sternohyoid,
             spinae is found as the semispinalis dorsi              sternothyroid, thyrohyoid, geniohyoid and

Questions:   How are epaxial muscles separated from the hypaxial    How do you know if the abdominal muscle is external,
             muscle in tetrapods?                                   internal or transversus?
Dermal muscles

   Chordate          Dermal muscles                    Location/function

Fishes        none                      none

Amphibians    cutaneous pectoris        on top of chest muscles; more prominent in toads
                                            than in frogs

Reptiles      costocutaneous parietal   in snakes (i.e. python), for progressive
                  muscles                    locomotion

Birds         none                      none
Mammals       mimetic muscles           muscles of facial expression; more commonly
                                           found in monkeys

              panniculus carnosus       stretching the entire back portion of many
                                             mammals, i.e. carabaos; used for moving the
                                             back without moving any other part of the
                                             body, to drive away birds and insects from
                                             the animal's back

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