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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