Download Comparative Anatomy Interactive Notes

Comparative Anatomy Notes – Set 8
MUSCLES
- as a whole, 2 groups of muscles attach to the skeleton:
1. Operate head, trunk, limbs
- provide locomotion and orientation
2. Operate visceral skeleton
- regulate feeding and respiratory movements
1. Somatic muscles
2. Visceral muscles
- visceral have exception = branchiomerics
- assist in feeding and resp. in lower vert.
- don’t follow characteristics of typical visceral muscles
- Somatic Muscles - skeletal muscles
- striated and voluntary
- Visceral Muscles - smooth muscle
- non-striated, involuntary
- except branchiomerics
- somatics arise from somites - myotome
Skeletal Muscles
- Axial
- Appendicular
- Branchiomerics
Axial - arise and insert on skull and vertebral column
Appendicular - insert on appendicular skeleton
Branchiomerics - attach to visceral skeleton
shark - epaxial and hypaxial muscles
- body wall muscles
- divided into 2 groups
amphibian - placement of muscle bundles
- epaxials are found above transverse process
- hypaxials along body wall proper
mammals - epaxials are subdivided
- hypaxials are more complex
- In amniotes
- epaxials have 3 groups
- transversospinalis, longissimus, iliocostalis
- transversospinalis - spinalis dorsi
- hypaxials - position
- dorsomedials, laterals, ventrals
- laterals - external oblique, internal oblique, and transverse abdominus
- most ventral of hypaxial in all vertebrates - rectus abdominus
- in head region above pharyngeal arches - somites break down
- they extend branchial tissue
- the rest go on to develop
- the ventral slips of post branchial somites extend forward and become hypobranchial
musculature
- these give rise to:
- sternohyoid
- sternothyroid
- omohyoid
- geniohyoid
- these support hyoid
- these muscles in addition to tongue
- hyoglossus
- styloglossus
- genioglossus
- lingualis propria
- all derived from hypobranchials
- these aid other groups of muscles that lie in this region
= branchiomerics
Branchiomerics
- striated muscle
- mandibular arch
- intermandibularis - digastric
- adductor mandibulae - masseter, temporalis
- hyoid arch
- sphincter coli - huge in Necturus
- in higher vert. more associated with skin in pharyngeal region
- platysma and mimetics - originated as branchiomerics but became attached to skin
- allows you to talk
- other arches
- trapezius (large fan shaped), sternomastoid, cleidomastoid
- Branchiomerics with pharyngeal arches arise from mesenchyme derived from splanchnopleure
- in lower vert. branchiomerics operate the gills
- when gills are lost they acquire new function associated with jaw, face, and shoulder
- Myotomal muscles are with appendages
- Appendicular muscles provide locomotion:
- 2 groups: 1. Extrinsic - have anatomical origin on axial skeleton or fascia of trunk
- insert on girdles and limbs
- ex. latissimus dorsi, levator scapulae ventralis
2. Intrinsic - origin on girdles or proximal skeletal elements of appendages
- insert on more distal elements
Extrinsic eye muscles
- look anteriorly
- eyeball is removed
- 6 eyeball muscles
- 2 obliques, 4 rectus
- 2 obliques on anterior portion
- superior and inferior
- 4 rectus arise in posterior portion of orbit
- the nerves that innervate these muscles
- oculomotor - 4
- trochlear - 1
- abducens – 1
Diaphragm - muscle, mammalian structure
- transverse septa that separates portion of fish
- covers the lungs and heart in abdominal cavity
2
Dermal and Integumentary Muscles
- in fish and tailed amphibians - skin is firmly attached to musculature
- can’t move skin independently to moving body
- 1st prominent dermal muscle that moves skin is found in reptiles = sphincter coli
- evolution of mammalian mimetics
- branchiomerics in origin
- dermal muscles
- as it spreads downward in neck, it become subdivided
- platysma - in neck
- in reptiles, rectilinear motion is done by costocutaneous muscles
- integumentary muscles reach peak in development in lover mammals
ex. Mole - entire body surrounded by sheath of dermal musculature
= panniculus carnosus
- monotremes also surrounded by wrap
- this muscle is thought to have been derived from latissimus dorsi and or
pectoralis
- higher mammals like horses and cows, muscle is used to shake skin
= cutaneous maximus
- cats cutaneous maximus is not as well developed
- comes off around pectoralis
patagial Muscles of bat wings - dermal muscle
- Mimetics of face of primates - dermal muscle that reached their peaks
- in man - auricularis – can move the ear; well-developed in canids and felids
- dogs - caninus muscle - raised in aggressive manner
- these are all extrinsic muscles
- there are intrinsic muscles within the skin
- arrectores plumarum (birds) and arrectores pilorum (mammals)
- arrectors pili
- errect the hair and feathers
- these are operated by visceral motor fibers
- erect upon change in disposition of organism
- Electric organs in fish
- modified hypaxial muscles that will discharge and deliver a zap to predator or means of food
gathering
- a freshwater catfish is covered with these organs
3