Muscles & Skeletons Flashcards
Hydrostatic Skeleton
Fluid held under pressure in a closed body compartment
Cnidarians
Jellyfish
1. Hydra can elongate by closing mouth
2. Muscles of gut cavity constrict
3. Water cannot be compressed
4. Therefore, decreasing cavity diameter forces length increase
How do flatwoms move
Movement results from localised muscle constriction on interstitial fluid.
How do nematodes move
Contractions of longitudinal muscles result in thrashing movements
Annelids
Use hydrostatic skeleton for peristalsis - control of form and movement using muscles to change shape of fluid filled segments
Structure of a worm
Made up of individual segments, each made up of circular and longitudinal muscle with bristles for anchorage
Hydrostatic skeleton pro and con
Pros - cushions organs for burrowing and crawling animals
Cons - Cannot support terrestrial activities off the ground (walking/running)
Exoskeleton
Hard encasement deposited on the surface of an animal
Molluscs
Snails, oysters etc
- Enclosed in CaCO3 shell
- Shell enlarged by adding to outer edge as animal grows
- Clams and bivalves hinge their shell by using muscles attached to the inside of the exoskeleton
Anthropods
Crickets, Bees, Xicadas
Exoskeleton is a cuticle, non-living coat secreted by epidermis
How do anthropods move
Muscles attach to knobs and plates on interior, joints have thing a flexible cuticle to allow movement
Anthropods cuticle composition
30-50% chitin and reminder is protein. Relative proportion of chitin and protein influence strength and flexibility.
Endoskeleton
Hard supporting elements such as bones buried in soft tissue
What kind of skeleton does a sponge have and why
Sponges have endoskeletons, their structure is internally reinforced by hard spicules of inorganic material or soft fibres of protein.
Echinoderms (kina)
Contains ossicles (hard plates) beneath skin that are MgCO3 and CaCO3 crystals bound together.
Sea stars vs Sea urchins ossicles
Ossicles are tightly bound in sea urchins as they have limited movement, however are loosely linked in sea stars to allow arms to change shape
What is a chordate
Vertebrates (endoskeleton)
Ligament
Connect bone to bone
Tendon
Connect muscle to bone
Axial Skeleton
Skull, vertebral column, rib cage
Appendicular Skeleton
Limb bones, pectoral and pelvic girdles
Ball and socket joint (example plus movement)
Humerus-shoulder, Femur Pelvic.
Allows rotation in several planes
Hinge Joint (example plus movement)
Humerus-Tibia, fingers, toes, ankles
Restrict movement to a single plane
Pivot (example plus movement)
Head on neck
Allows rotation
How does size correlate to structure
Animals body structure must support its size - Large animals have and NEED different proportions to small ones.
Skeletal Muscle
Bundle of long fibres running parallel to length of the muscle - one fibre = one cell
Myofibril
Tubular organelle containing thin and thick filaments
Thin Filament
Consist of two strainds of actin coiled together
What is thick filament made of
Myosin
Why is skeletal muscle called striated muscle
Regular arrangement of myofilaments create a pattern of light and dark bands