Avian Skeleton Flashcards
Skeleton Functions
Support, protection, articulation of appendages, blood cell production, and calcium stores
Axial skeleton
Head spine and tail
Skull
Large orbits to accommodate large eyes for good sight
Occipital condyle
One to articulate spine while mammals have 2
Cranial kinesis
High ability to unhinged the jaw to swallow large prey
Heterocoelius
Centrum in cervical vertebrae allows for a high degree of neck mobility; each vertebrae moves a little bit further
Uncinate process
Fuses the ribcage together for flight rigidity and serves as an attachment point for scapula muscles; short in walking birds, intermediate in non specialists, and long in diving birds
Synsacrum
Lumbar, sacral, and some caudal vertebrae fused into a solid structure which is fused to the pelvis; allows Legs to support the body
Pygostyle
Fused causal vertebrae at the end of the reduced tail, attachment site for tail feathers
Appendiculur skeleton
Appendages including pectoral girdle, wings, pelvic girdle, and legs
Pectoral girdle
Forms a tripod of bones to transfer energy from wing thrust to the body
Scapula
Runs along the spinal column bracing the shoulder against displacement from flapping
Coracoid
Braces the sternum against compression resulting from contraction of the pectoralis, prevents the ribcage from collapsing
Furcula
Wishbone; strut that braces the wings apart, acts as a spring aiding in the downstroke
Wing
Highly modified forelimb that folds against the body in a z shape; the humerus is a shortened and broadened upper arm, reduced number of wrist hand and finger bones are fused
Pelvic girdle
Lengthened and fused to the synsacrum forms a roof covering half of the body allowing the legs to support the body; pubis and ischium open ventrally to accommodate egg laying
Legs
Spaced far apart by the fused pelvis; femur buried in the body, forward facing to support center of gravity and exposed tibiometatarsus
Cnemial crest
Tibial extension at the knee joint well developed in divers, allows for oar like leverage from the legs for swimming and prevents splaying
Tarsometatarsus
Elongated heel bone, typically the unfeathered leg piece connecting to 2 3 or 4 toes
Bird musculature
Serves for posture, flight, and thermogenesis; shifted ventrally for aerodynamics supported by the fused vertebral column
Flight muscles
Pectoralis powers up stroke, originates on the pectoral girdle and inserts on ventral humerus; supercorracoideus powers the downstroke originates on the sternum and passes through the triossial canal before inserting on dorsal humerus
Slow tonic muscle fibers
Slow contracting fatigue resistant, low energy use and low power, highly aerobic red muscle
Fast twitch glycolytic fibers
Fast contracting, fatigue rapidly, few mitochondria, white muscle
Fast twitch oxidative glycolytic fibers (FOG)
Fast contracting, high levels of oxidative and glycolytic enzymes, high mitochondria levels, fatigue resistant intermediate muscles; most common in birds that fly a lot
Shivering
Mechanism of heat production in birds; isometric antagonistic muscle groups exert equal and opposite force to limit surface disturbance
Burst shivering
As temperature decreases amplitude and duration of shivering increases; cold acclimation leads to decreased amplitude in the same cold stress
Non shivering thermogenesis
Heat production without shivering, done by brown fat in mammals; likely occurs in birds but method is unknown
