Comparative Anatomy
Muscles
Kardong
Chapter 10
Part 10
Muscles
Two major muscle categories:
 Somatic muscles
Operate head, trunk, limbs
 Locomotion and orientation


Visceral muscles
Operate visceral skeleton
 Digestion and respiratory movements

More on the two Muscle
Groupings

Somatic muscles
Skeletal muscle
 Striated and voluntary


Visceral muscles
Smooth muscle
 Non-striated and involuntary
 Exception- branchiomerics (unsegmented)

Skeletal Muscle Microanatomy
Figure 10.1 (book
figure 10.2).
Cardiac Muscle Microanatomy
Figure 10.2 (book
figure 10.3).
Smooth Muscle Microanatomy
Figure 10.3 (book
figure 10.4).
Skeletal Muscles

Axial


Appendicular


Trunk and tail
Insert on girdles, fins, or limbs
Branchiomerics

Attached to visceral skeleton
Origin of Muscle Groups
Derived from Embryonic
Myotomes
Figure 10.4. (book figure 10.21).
Axial Musculature

Shark
Epaxial and hypaxial
muscles
 Body wall muscles


Amphibians
Epaxials above
transverse process
 Hypaxials along body
wall proper


Mammals
Epaxials subdivided
 Hypaxials more complex

Figure 10.5. Trunk muscles of vertebrates.
Abdominal Muscle Groups - Amniotes


Epaxials
 Transversospinalis,
longissimus, iliocostalis
Hypaxials
 Dorsomedials, laterals,
ventrals
 Laterals- external oblique,
internal oblique, and
transverse abdominus
 Ventral- rectus abdominus
Figure 10.6. Epaxial and hypaxial muscles
Epaxial and Hypaxial Muscles - Amniotes
Figure 10.7. Epaxial and hypaxial mucles.
Figure 10.8. Specific epaxial muscles.
Head Region
Figures 10.9. Myotomes in the head, neck,
and thoracic regions of the embryo.
Figure 10.10. Axial muscle origin and
innervation in vertebrate embryo.
Head Region



In branchial region, somites are broken down
Ventral slips of postbranchial somites become
hypobranchial musculature
Hypobranchial muscles give rise to:




Sternohyoid
Sternothyroid
Omohyoid
Tongue muslces





Geniohyoid
Hyoglossus
Styloglossus
Genioglossus
Lingualis propria
Figure 10.11. (book figure 10.30).
Appendicular Muscles

Extrinsic
Origin on axial skeleton or fascia of trunk
 Insert on girdles and limbs


Intrinsic
Origin on girdles or proximal skeletal elements of
appendages
 Insert on more distal skeletal elements

Intrinsic Muscles
Figure 10.12. Intrinsic muscles of pectoral girdle and forelimbs of mammals and their
homologues in reptiles.
Branchiomerics




Arises from lateral mesoderm
Mandibular (1st) arch
Hyoid arch
Arches IV to VI
Branchiomeric Muscles
Figure 10.13. Branchiomeric muscles and their innervations (see book table 10.3).
Branchiomerics



Mandibular (1st) arch
 Intermandibularis - digastic
 Adductor mandibulae - masseter, temporalis
Hyoid arch
 Sphincter coli
 Platysma and mimetics
 integumentary muscles
Arches IV to VI
 Trapezius, sternomastoid,
cleidomastoid
Figure 10.14. Branchiomeric muscles of
gnathostomes.
Nerves Innervating Muscles
Figure 10.15. Facial nerves to muscles.
Figure 10.16. Cranial nerves.
Extrinsic Eye Muscles

Six eyeball muscles

2 obliques
 Superior
and inferior on
anterior portion

4 rectus
 Arise
in posterior
portion of orbit
 Innervated by
oculomotor, trochlear,
and abducens
Figure 10.17. Innervation of eye muscle
in embryo.
Extrinsic Eye Muscles
Figure 10.18. Dorsal view of extrinsic
muscles of the left eyeball .
Figure 10.19. Lateral view of extrinsic
muscles of eyeball.
Diaphragm


Mammalian muscle structure
Near lungs and heart in abdominal cavity
Figure 10.20. Human diaphragm.
Dermal or Integumentary Muscles


Fish & tailed amphibiansskin is firmly attached to
musculature
Sphincter coli- first
muscle to move skin


Subdivides down neckplatysma
Extrinsic and intrinsic
muscle groups
Figure 10.21. Evolution of mammalian facial
muscles. Shows sphincter colli (SC) spreading
into platysma (P).
Extrinsic Integumentary Muscles






Costocutaneous muscles - allows rectilinear motion
(reptiles)
Panniculus carnosus - sheet surrounds body
Cutaneous maximus - to shake skin (higher mammals)
Patagial muscles - bat wings
Auricularis - moves human ear
Caninus muscle - arises with aggression
Intrinsic Integumentary Muscles

Arrectores plumarum (birds) & arrectores pilorum
(mammals) - erects hair and feathers
Specialized Muscles

Electric organs
In elasmobranchs and bony fish
 Modified hypaxial muscles

Figure 10.22. Electric eel.
Vertebrates with Electric Organs
Figure 10.23. (book figure 10.1).