skeletons
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Skeletons. All the struts, none of the ties; strut resists compression, tie resists tension “the form of an object is a diagram of forces”; translocation of forces (tensions, compressions are forces), joints (of bones and leg segments), origins and insertions: - PowerPoint PPT PresentationTRANSCRIPT
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Skeletons
•All the struts, none of the ties; strut resists compression, tie resists tension•“the form of an object is a diagram of forces”; translocation of forces (tensions,
compressions are forces), joints (of bones and leg segments), origins and insertions:
• Three skeletal forms: hydrostatic, endoskeleton, exoskeleton• Examples: Frog leg; insect mandible; segmented worm coelom
•Frog: femur, tibiofibula, astralagus (ankle); gastrocnemius, Achilles’ tendon etc.• Grasshopper cranium: adductor and abductor apodemes
•Appendage movments: adduction vs abduction; promotor vs remotor, depressor vs elevator, extensor vs flexor, retractor vs protractor
•Annelida: leech looping locomotion; why are earthworms metameric? coelom, peristaltic burrowing: outer circular, inner longitudinal muscle; incompressible
coelomic fluid etc.; flatworm in a burrow?• Unshortening muscles:
•Anatagonists : tibialis anticus longus vs plantaris; adductor mandibular muscle vs abductor mandibular muscle; circulars vs longitudinals
• Elastic energy storage; scallop hinge; abductin, resilin•Pinnate fibre arrangement on blade apodeme: plantaris (gastrocnemius),
mandibular adductor etc: high force, short distance• Muscles of frog jump: elasticity influences muscle operating length
• Leg segments, cylinders of exoskeleton, half-moon membranes
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Endoskeleton and frog jump; exoskeleton and chewing
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FlatwormsPhylum Platyhelmintheslocomotion by cilia and
body waves
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Christmas Tree worms, Phylum Annelida
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From Wikkimedia Commonspictures by Hans Hillewaert
Nereis succinia epitoke of polychaete worm
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Phylum Annelidamostly marine
Lumbricusearthworm
• The adaptiveness of a segmented body: outer circular and inner longitudinal muscles, septa (septum sing.) fore and aft compartmentalize the coelom; muscles made antagonists by the fluid skeleton: the coelomic fluid, which translocates forces; moving in a burrow
Univ of Wisconsin
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Transverse section Lumbricus
Coelom: fluid-filled cavity formed in mesoderm, functions as hydrostatic skeleton to translocate forces generated by circular and longitudinal muscle antagonists
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Rana skeleton: modifications for jumping (saltatorial adaptation): pelvic girdle: pubis, ischium, ileum; see urostyle. ‘tarsal bones’ just beyond ankle
joint
Gastrocnemius or[= plantaris] muscle: originates on femur and inserts on bones beyond the ankle joint; its contraction contributes to extension of limb
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Frog’s legs (Rana catesbeiana, bullfrog ) ready for the chef: note the gastrocnemius and white associated Achilles’ tendons
Marinex Co.(Seafood) Taiwan
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Picture credit: National geographicLanding isalso important and pectoralgirdle reflectsdesign to dissipatekinetic energy of jump