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Skeletons

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), joints, origins and insertions: Three skeletal forms: hydrostatic, endoskeleton, exoskeleton

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Skeletons

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  1. 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), joints, 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; promotorvsremotor, 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 : tibialisanticuslongusvsplantaris; adductor mandibular muscle vs abductor mandibular muscle; circulars vslongitudinals 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 Shock absorbers: cartilage: pectoral girdle frog Synovial fluid: lubrication Joint planes change proceeding distally on crayfish claw, half-moon membranes

  2. Endoskeleton and frog jump; exoskeleton and chewing

  3. FlatwormsPhylum Platyhelmintheslocomotion by cilia and body waves

  4. Christmas Tree worms, Phylum Annelida

  5. From Wikkimedia Commonspictures by Hans Hillewaert Nereissucciniaepitoke of polychaete worm

  6. Phylum Annelidamostly marineLumbricusearthworm • 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

  7. Transverse section Lumbricus

  8. Frog’s legs ready for the chef: note the gastrocnemius and white associated Achilles’ tendons

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