Transcript Muscles
VERTEBRATE ZOOLOGY (VZ Lecture24 – Spring 2012 Althoff - reference PJH Chapters 16-17) Birds – Part II Bill Horn Body Form and Skeleton • Feathers: molded for aerodynamic forces; light, strong…very resilient for their weight • Skeleton: a) skull is remarkably light b) wing bones air filled c) leg bones heavier than same-sized mammal *overall: more mass is concentrated in ____________ than comparable sized mammals Body organ “reductions” • Birds ______ urinary bladders • Most birds have only one ovary (or only one _______________ ovary) • _________ of both sexes are usually small (with hypertrophy or regression depending on time of year) Muscle & Cardiovascular Output • Pectoral muscles (major wing musclesdownstroke) may account for ______ of total body mass of strong fliers --power output per unit of mass for dove estimated to be 10-20x that of most mammalia muscles • _______ heart and high rates of blood flow coupled with complex lungs that a) maximize gas exchange b) dissipate heat produced by high levels of muscular activity during flight FAVEOLAR LUNG Streamlining • Birds _____ vertebrates that move fast enough for wind resistance and streamlining to be important • “Fast birds” songbirds: up to 50 km per hour ducks & geese: up to 80-90 km per hour peregrine falcon: 200 km per hour in dive Structural characteristics like fast-flying aircraft: ______________ make smooth joints between wings and body, and head and body ___________ close to body in flight Not-so-streamlined • Some birds are slow fliers….slow to launch into flight, slow in-flight • “Slow birds” spoonbills flamingos herons cranes Structural characteristics opposite of fast-flying aircraft: long-legged with legs that trail behind and/or not tucked up under the body long-necks extended Air-filled bones…fused and thinner bones • • • • Also referred to as ____________ bones Not present in all birds Better developed in larger birds than smaller birds Diving birds (penguins, grebes, and loons) have little pneumaticity in their bones • Skeletons of most birds exhibit some pneumaticity in pectoral girdle and humerous • Pelvic girdle: elongated with ischium and ilium broader and much thinner than ancestral reptile line….and combined with the synsacrum—a fusion of 10-23 vertebrate…. pygostyle—fused caudal vertebrate Fusion of vertebrae means more rigidity • Overall, reduction in number of vertebrae and fusion of vertebrae…and relatively immobile thoraic vertebrae…in combination with elongated, “rooflike” pelvis produce a nearly RIGID vertebral column. • The rigid “trunk” is balanced on the legs • Femur projects to the anterior…combined with articulation of with the tibiotarsus and fibula results in this being the bird’s center of gravity center of gravity Other “skeleton” features of note…. • Wings positioned above the center of gravity • Sternum greatly enlarged (most with keels…as noted) for greater amount of surface area • Scapula extends posteriorly above ribs and is supported by coracoid which is fused ventrally to the sternum • Clavicles project to anterior—usually fused to form the furcula (wishbone)… provides additional bracing • Hind foot typically greatly elongated with ankle joing within the tarsals • Tarsometatarsusmetatarsals of some toes fused with the distal tarsals • Tibiotarsustibia fused with proximal tarsal bones Muscles – Mass distribution differences • Hummingbirds & swallows mostly flight • Predatory birds flight but use legs to capture prey • Swimming birds • “Terrestrial” birds --run instead of fly to flee flight muscles ________ of total body mass, legs _____ flight muscles ~_____ of total body mass, leg _____ limb & flight muscles about equal percentage, overall _______ of total body mass limb muscle mass ___ than flight muscle mass Muscles • Two basic processes “fuel” muscle contract: a) ____________ metabolic pathways --achieve “quick” response --does not requires O2 --more fast-twitch muscle fibers, relative to slow-twitch muscle fibers b) ___________ metabolic pathways --achieve “sustained” response --requires O2 --more slow-twitch muscle fibers, relative to fast-twitch muscle fibers --slow-twitch muscle fibers contain lots of _____________ Fast vs. Slow Twitch Muscle Fibers Category Slow-Twitch _____________ more _____________ more Myoglobin more Color appearance red-brown ____________ build-up lower Fatigue slower Fast-Twitch fewer less less white higher quicker Muscles & Birds Other “flier” vs. “runner” differences • Composition of leg muscles indicates regular, sustainable activity • Composition of breast muscles (major muscle groups responsible for up- and downstroke of wings) indicative to long vs. short flight capabilities • Fliers—(think songbirds, waterfowl, etc.) a) legs: large amounts of myoglobin b) breast: large amounts of myoglobin • Runners—(think quail, pheasant, wild turkey) a) legs: large amounts of myoglobin b) breast: essentially lack myoglobin Major Flight Muscles ↓ __________________ – origin on keel of sternum (lateral side) and inserts at humerus on ventral side contracts for ______________ relaxes during upstroke ↑ _________________ – origin on keel of sternum (lateral side), passes through foramen triosseum, inserts (tendon) on dorsal head of humerus. Foramen trosseum formed by articulation of the furcula, coracoid, and scapula. relaxes during downstroke contracts for ______________ pectoralis supracoracoideus Foramen triosseum __________________ Major Feather Types on the Wing Primaries (remiges = wing feathers) Secondaries (remiges = wing feathers) Major coverts – leading edge of wing Alula—forms wing slot on leading edge (at carpal bones Major Feather Types on the Wing Fig. 17-8 p444, PJH