Exam 2 Comparative Anatomy 13: Musculature II:Axial and Branchiomeric Musculature

*List and characterize the three groups of skeletal muscles*

Axial, Brachiomeric, Appendicular

*Identify the specific cranial nerve (by name and number) associated with each of the six gill arch pairs.*

• *Gill arch I (mandibular):* Innervated by CN V: (trigeminal nerve). • *Gill arch II (hyoid):* • Innervated by CN VII: (facial nerve). • *Gill arch III:* • Innervated by CN IX: (glossopharyngeal nerve). • *Remaining gill arches:* • Innervated by CN X:(vagus nerve).

Gill arch 3 innervated by

CN IX

Gill arch 1 innervated by

CN V

Gill arch 2 innervated by

CN VII

All remaining gill arches

CN X

Adductor mandibulae

Closes the sharks mouth. big strong muscle

What muscles are derived from the second brachial arch?

Hyoid arch- attach to hyoid skeleton, form lower jaw, and operculum in fishes. (CN VII)

What type of muscle are the mammalian diaphragm and cremaster muscles?

Hypaxial muscles

Describe segmentation of fish compared to tetrapods

Hypaxial muscles divide into layers...the segmentation seen in fish is not as prominent in tetrapods --additional information Epaxial muscle is reduced. tetrapods have rectus abdominus (rectus cervicis in neck)

Deep: Intermediate

Iliocostalis Longissimus Spinalis

*Differentiate the extrinsic from the intrinsic back muscles in mammals.*

Superficial -Extrinsic intermediate -Extrinsic Deep -Intrinsic

Muscles of the eye for CN IV (trochlear)

Superior oblique

How many muscles do the three CN innervate in the eye.

Trochlear nerve (CN IV) innervates 1 Abducens nerve (CN VI) innervates 1 Oculomotor nerve (CN III) innervates 4

Superficial back muscles

spinotransversalis system: connect limb to axial skeleton. • Muscles run laterally and upward to attach to transverse processes and skull. Innervated by ventral rami or CN XI. (Hypaxial) • Trapezius • Latissimus dorsi • Levator scapulae • Rhomboideus major • Rhomboideus minor

What does the sphincter colli of lower tetrapods form?

spreads of the head of amniotes to become the platysma and muscles of facial expression

Identify the three groups of intrinsic back muscles in mammals.

transversospinalis system: Run up and in True intrinsic muscles of the back are innervated by *dorsal rami. (Epaxial)* - *Superficial* • Splenius capitis • Spleniua cervicis - *Intermediate* • Iliocostalis • Longissimus • Spinalis - *Deep* • Semispinalis • Multifidus • Rotatores

Intermediate back muscles

Sacrospinalis system: Hold your back erect Innervated by ventral (anterior) rami. (Hypaxial) Serratus posterior group: • Serratus posterior superior • Serratus posterior inferior

Deep: Deep

Semispinalis Multifidus Rotatores

*Describe the axial musculature of an amniote (reptile and mammal) and relate to that of a typical fish and an amphibian.*

*Amniote from Amphibian: Epaxial* Epaxial musculature (dorsalis truncus) is divided even further into • Dorsalis truncus subdivided into three longitudinal columns: - Transversospinalis (or spinalis). - Longissimus dorsi. - Iliocostalis. -quadratus lumborum • Epaxial muscles reduced in turtles. because of shell *Amniote from Amphibian: hypaxial* • Hypaxial muscles divided into three layers as in amphibians. (three lateral layers and a ventral group) • Those in thoracic area are interrupted by ribs. Ribs interrupt flank muscles, they run in between the ribs..become intercostal muscles.

From Fish to tetrapod to mammal Muscle homologies: *Levator palatoquadrati,preorbitalis, adductor mandibulae*

*Tetrapod:* Adductor mandibulae *Mammal:* Masseter,temporalis, lateral/medial pterygoids and tiny ear muscles

From Fish to tetrapod to mammal Muscle homologies: *Levator hyoideus*

*Tetrapod:* Brachiohyoideus *Mammal:* facial expression

From Fish to tetrapod to mammal Muscle homologies: *gill arch levators*

*Tetrapod:* Cucullaris + levatores arcumm *Mammal:* Trapezius and sternocleidomastoid

From Fish to tetrapod to mammal Muscle homologies: *Hyoid constrictor*

*Tetrapod:* Depressor mandibulae *Mammal:* Posterior digastric (CN 5 gill arch 1)

From Fish to tetrapod to mammal Muscle homologies: *Intermandibularis*

*Tetrapod:* Intermandibularis *Mammal:* Mylohyoid and anterior digastric (CN 7 gill arch 2)

From Fish to tetrapod to mammal Muscle homologies: *Coracoarcuals, coracohyoid*

*Tetrapod:* Rectus cervicis *Mammal:* Sternohyoid, omohyoid, (also, thyrohyoid in mammals)

From Fish to tetrapod to mammal Muscle homologies: *Coracomandibularis*

*Tetrapod:* genioglossus and geniohyoid *Mammal:* Genioglossus and geniohyoid (chin)

From Fish to tetrapod to mammal Muscle homologies: *interhyoideus*

*Tetrapod:*interhyoideus and sphincter colli *Mammal:* facial expression

The cranial nerves innervate the 6 muscles of the eye

*Trochlear nerve (CN IV)* • superior oblique muscle. *Abducens nerve (CN VI)* • lateral rectus muscle. *Oculomotor nerve (CN III)* • Inferior oblique • Inferior rectus • Medial rectus • Superior rectus

Epaxial and hypaxial separation

*hypaxial* muscles, which lie ventral to the horizontal septum of the vertebrae *epaxial* muscles, which lie dorsal to the septum

What are extrinsic muscles?

*originate* from axial and *insert* on girdle or limb -Most of muscles in fishes

What are intrinsic muscles?

*originate* from girdle or limb and *insert* distally Develop within the limb in tetrapods

List and describe the function(s) of the mammalian muscles of mastication and their innervation.

All innervated by mandibular branch *CN V* Masseter Temporalis Lateral pterygoid medial pterygoid

superficial constrictor in the gills what happens if it comes together versus elongates?

Bring the two components together will make it more round which will open the gill arch. When the articulation is straight it will close the gill opening.

How are epaxial and hypaxial parts separated?

By horizontal septum. This is not present in cyclostomes

How are Epaxial musculature innervated?

Dorsal rami of spinal nerves

What are the amphibian back muscles? Amphibian ventral muscles?

Dorsalis truncus and subvertebral rectus abdominus

How to differentiate Epaxial versus Hypaxial and extrinsic versus intrinsic?

Epaxial - dorsal rami Hypaxial - ventral rami ------- • Extrinsic appendicular muscles originate from the axial skeleton and insert on the girdle or limb. • Intrinsic appendicular muscles originate from the girdle or proximal limb and insert more distally.

Axial muscles are divided into?

Epaxial and hypaxial

What are the amphibian Axial flank muscles?

External oblique Internal oblique Transversus They run in opposite directions and cause flexion extension of body trunk.

Describe hypaxial muscles in reptiles and mammals

External oblique internal oblique transversus

What is the subdivision of appendicular muscles?

Extrinsic and intrinsic

Muscles of the eye for CN III (oculomotor)

Inferior oblique Inferior rectus Medial rectus Superior rectus

What two muscles are in fish but lost to all tetrapods?

Interarcuals Coracobrachialis

What muscles are derived from first brachial arch?

Mandibular arch- open and close the jaws (CN V)

*Be able to describe the musculature associated with a typical gill arch of a fish (i.e., shark).*

Muscles of the gill arch region arise from the embryonic mesenchyme instead of somites. • More anterior ones are striated. (voluntary) • More posterior ones are smooth. (involuntary) • Each set is associated with a gill arch. from the first two points: Transition reflects change from vigorous movements required for feeding and gill function to slower, sustained movements required for transport of food along gut tract.

Define "myomere."

Myomere are the blocks of skeletal muscle tissue found commonly in chordates. They are commonly zig-zag, "W" or "V"-shaped muscle fibers. The myomeres are separated from adjacent myomere by connective tissues

What muscles are derived from the remaining arches?

Remaining arches operate gills in fishes and take on new function in tetrapods: Cucullaris of fishes give rise to trapezius and sternocleidomastoid of amniotes. Innervated by (CN IX,X)

Describe axial muscles in Reptiles and Mammals

Spinalis longissium iliocostalis quadrates lumborum

Deep: Superficial

Splenius capitis (Attach to head) Splenius cervicis (cervical vertebrae attachment)

Explain why the mammalian digastric muscle has two sources of innervation.

The two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves. Anterior digastric (CN 7 - gill arch 2) Posterior digastric (CN 5 - gill arch 1)

How are Hypaxial musculature innervated?

Ventral rami of spinal nerves

Two ways extrinsic muscle develop in tetrapods?

Within embryonic wall and spread to limb Develop in limb and spread to axial skeleton

Muscles of the eye for CN VI (adducens)

lateral rectus

*Axial muscles*

• Derived directly from *myotome portions of somites* • Demonstrate a segmental arrangement (metamerism) • Innervated by* spinal nerves*

*Describe the axial musculature of the amphibian and relate to that of a typical fish.*

• Division of hypaxial muscles into layers. • Increase in mass and complexity of limb muscles. • Reduction in epaxial musculature: - Still somewhat prominent in urodeles. - Useful in flexing body axis for swimming. -*Epaxial muscle becomes* the dorsals truncus and subvertebral

What do the hypaxial muscles become in the ribs?

• External oblique -> External intercostals • Internal oblique -> Internal intercostals • Transversus -> Subcostals

*Brachiomeric muscles*

• Formed from *embryonic mesenchyme associated with pharyngeal arches* • Demonstrate a segmental arrangement (metamerism) • Innervated by* cranial nerves*

*Appendicular muscles*

• Formed from limb bud mesenchyme • Innervated by *spinal nerves* Reminder: The skeletal muscles are divided into axial (muscles of the trunk and head) and appendicular (muscles of the arms and legs) categories.

How are myomeres separated?

• Individual myomeres are separated from each other by vertical connective tissue partitions: myosepta

Describe function and origin/insertion for: Medial Pterygoid

• Lateral pterygoid plate and maxilla to medial surface of mandible near angle • Elevates, protracts, grinding (unilateral)

Describe function and origin/insertion for: Lateral Pterygoid

• Lateral pterygoid plate and sphenoid to front of mandible and TMJ • Protracts mandible; depresses chin (bilateral; grinding (unilateral)

*Eye musculature and innervation, how many muscles are associated with each eye and how many somites?*

• Six extrinsic eye muscles are associated with each eye ball. • These muscles are derived from three pairs of anterior somites. • Therefore, three pairs of cranial nerves innervate these muscles. ( III, IV, VI)

Describe function and origin/insertion for: Temporalis

• Temporal fossa and fascia to coronoid process • Elevates and retracts mandible

*Distinguish between epaxial and hypaxial muscles and relate to connective tissue partitions that compartmentalize the myomeres and axial muscle groups.*

• The epaxial and hypaxial parts are separated from each other by a fibrous tissue partition,*the horizontal septum*: -Not present in cyclostomes • Individual myomeres are separated from each other by vertical connective tissue partitions: -Transverse septa myosepta separate myomeres

Describe function and origin/insertion for: Masseter

• Zygomatic bone to lateral surface of ramus and coronoid process • Elevates and protracts mandible