Avian Anatomy and Physiology (3) PDF

Skin ▪ Epidermis- very thin, has keratin that produces the scales, feathers, and outer sheaths of beak and claws ▪ Dermis- thicker but still thin, stores fat for insulation and nutrition ▪ Smooth muscles to innervate feather follicles for thermoregulation – Puff up- trap heat – Against b...

Skin ▪ Epidermis- very thin, has keratin that produces the scales, feathers, and outer sheaths of beak and claws ▪ Dermis- thicker but still thin, stores fat for insulation and nutrition ▪ Smooth muscles to innervate feather follicles for thermoregulation – Puff up- trap heat – Against body- promotes heat loss  Uropygial Gland “preen gland” ▪ Dorsal surface at upper base of tail ▪ Produces an oily/fatty substance ▪ Used for cleaning and waterproofing ▪ Larger in aquatic/tropical species ▪ Lacking in ostriches, some psittacines, and in a few other species  Claws and Beak ▪ Beak- tough, horny epidermal covering, continually grows, size, shape, and hardness varies with function ▪ Claws- different types depending on habit – BOP- talons  Feathers ▪ Outgrowths of skin, made of protein, nonliving structures- 4%-12% of body weight, only have sensation at the base ▪ Enable flight, protection, thermoregulation, camouflage, and communication behaviors ▪ Different types for different functions  Feather Anatomy ▪ Rachis- main feather shaft ▪ Inferior umbilicus- opening at base ▪ Superior umbilicus- openings on shaft where webbed part begins ▪ Calamus- hallow part that extends from inferior to superior umbilicus  Feather Anatomy ▪ Vane- flattened part that appears web like ▪ Barb- projections that comprise a vein ▪ Barbules- microscopic projections that maintain feather structure ▪ Hamuli- hooklets- interlock barbs with adjacent ones forming a flexible web  Feather Growth ▪ Originate from seven tracts called pterylae ▪ Apteria- bare areas of skin ▪ Fault bars-stress bars- weakened area on vane that lacks barbules, caused by stress during development, the rachis is pinched depleting blood supply. Blood supply returns when stessor is removed – Nutrition is most common cause  Molting ▪ Process of feather replacement, requires a large amount of energy, one to several times per year ▪ Develop from papillae in dermis and contain germ cells – Activated by physiological and environmental factors – Newly developed feather pushes old one out  Molting ▪ New feather covered by periderm-epidermal covering, removed by preening – Blood vessels reach into new feather – When fully developed, blood dries up and the rachis is pinched  Muscles ▪ Special muscles have been developed for flying, most being placed ventrally ▪ 175-200 muscles ▪ White- thick, low blood supply and little myoglobin- short distance flyers ▪ Red- thinner, rich blood supply, fat, myoglobin, and mitochondria- long distance fliers  Muscles ▪ Pectoralis-breast muscle- inserts on underside of humerus – Compression causes depression of wing – Common place for IM injection  Muscles ▪ Supracoracoideus- turns into tendon that passes through cavity formed by shoulder girdle and inserts in top of the humerus – Counteraction- upstroke of wing – In long distance fliers these two muscles comprise 20%-25% of body weight  Muscles ▪ Muscles of femur can control movement in distal leg and toes via tendons – Perching reflex- when legs bend to perch, tendons bend and pull toes closed around perch, may also be used for predation  Skeleton ▪ Must support flight and walking ▪ Modifications to support flight – Reduction in the number of bones – Fusion of bones to form plates that provide strength and simplify movements – Reduction in density, strengthened by a network of internal bony braces – Loss of internal bone matrix  Bones- Skull ▪ Large portion of skull devoted to protecting eyes – Sclerotic ring- ring of protective bony plates  Bones- Sternum ▪ Large and concave- place of origin for flight muscles ▪ Keel- large bony ridge – Lacks in flightless birds – Large in long fliers – Smaller in short fliers  Bones- wings ▪ Long in birds that glide or soar ▪ Shorter in birds that flap ▪ Ulna has a larger diameter than radius  Sense organs- Vision ▪ Good vision essential for life ▪ Optic lobe takes up most of midbrain ▪ Shape- round, flat, or tubular – Diurnal- round/relatively flat – Nocturnal- tubular with large pupils  Vision ▪ Nictitating membrane- lubricate and protect eyes, voluntary control (striated muscles) ▪ Iris- striated muscles- PLR’s not good diagnostic tool ▪ Pecton- in vitreous, distributes nutrition, ribbon like structure- very vascular – 30% of traumatized birds suffer hemorrhage from pecton  Photoreception ▪ Retina only slightly vascularized which helps decrease interruption of image – 1.5-2 times the amount of photoreceptors than any other vertebrate – Each cone is attached to single nerve fiber – Some birds have 2 fovea- funnel shaped area with high concentrations of cones – Color vision not completely understood – Some can detect UV light- diurnal species  Hearing ▪ Structure simpler than in mammals – Middle ear contains a single bone, the columella, that connects to the inner ear. It functions as a funnel for sound – Nocturnal species rely on hearing for predation  Taste ▪ Only contain 50-400 taste buds (humans have 10,000) – Located on side of tongue and soft palate – Sensitivities and thresholds are specific for each species  Touch ▪ Have 2 types of sensory nerve endings that are primarily used for finding food and protection – Grandy’s corpuscle- tongue and palate – Herbst corpuscle- tongue, palate, beak, cloaca, legs, wings, uropygial gland, and bases of many feathers ▪ Auriculars- contour feathers around ears  Smell ▪ Varies widely between species – Some species smell is highly developed – Food and reproduction  Digestive system ▪ Fast metabolism and high energy demand – Assimilate 60%- 99% of energy consumed  Digestive System ▪ Bill- size and shape varies with diet ▪ Mouth- psittacines have very muscular tongue ▪ Esophagus- right side of neck – Crop- storage pouch for food ▪ Single or double pouched, birds with well developed crop eat few larger meals, small crops forage all day ▪ Regulates passage of food  Stomach – Proventriculus- anterior chamber- chemical digestion – Ventriculus- gizzard- grind food components – Indigestible food regurgitated into pellets  Digestive system ▪ Liver- bilobed- right larger than left ▪ Pancreas- relatively large- larger in fish/grain eaters ▪ Cloaca – Coprodeum- fecal matter – Urodeum- discharge from kidneys/genital duct – Proctodeum- stores excrement  Circulatory System ▪ Blood – Nucleated red blood cells, oval shaped – Heterophils=neutrophil – Passerines- blood formed in spleen and liver  Circulatory System ▪ Renal portal system – Blood returning from the iliac veins travel to kidneys – Valves at the junction of iliac and renal veins steer blood to kidneys or to heart via the posterior vena cava  Respiratory System ▪ Choanae- internal nares open from nasal cavity to roof of mouth ▪ Syrinx- enlargement of trachea cranial to sternum- voice box ▪ Trachea- complete tracheal rings ▪ Bronchi- extend to air sacs ▪ Mesobronchi- once enter lungs  Respiratory System ▪ Ventrobronchi- 4 sets- supply different parts of the lung with air ▪ Parabronchi- connected to air capillaries- gas exchange  Air Sacs ▪ 2 cranial thoracic, 2 caudal thoracic, 2 cervical, 2 abdominal, and 1 interclavicular – Reservoirs for air – Provide warmth and moisture to facilitate diffusion – Thermoregulate- internal evaporation – Provide buoyancy  Lungs ▪ Small and attached to thoracic vertebrae and ribs ▪ Bright red, highly vascularized, and inelastic ▪ Unidirectional air way  Respiratory Cycle ▪ First inhalation- expansion of coelomic cavity creates pressure gradient, air flows to posterior air sacs ▪ First exhalation- air pushed into lungs- gas exchange occurs ▪ Second inhalation- out of lungs and into anterior air sacs ▪ Second exhalation- air leaves body through trachea  Respiratory Cycle ▪ Fresh air flows in a continuous unidirectional path in lungs ▪ There is no mixed air or residual air  Urogenital- Kidneys ▪ Elongated and do not contain a renal pelvis ▪ Urine composition- 75% uric acid- white stuff- urates ▪ More efficient in elimination of nitrogen ▪ Conserves water ▪ Survival of embryos- less water to store AvianRenalPelvis_small  Male Reproductive Tract ▪ Gonads enlarge during breeding ▪ Bean shaped ▪ Psittacines- sperm passed to vagina via contact with female cloacae  Female Reproductive Tract ▪ Oviduct comprises five sections – Infundibulum- grabs ovum as it comes out of ovary – Magnum- secretes layers of albumin (egg whites) – Isthmus- deposits keratin shell membrane – Uterus (shell gland)- deposits water, albumin, hard external shell, and pigmentation – Vagina- secretes mucous for oviposition, can store sperm for hours to days  Females cont. ▪ Right ovary is rudimentary and not functional ▪ Determinate- specific # of follicles ▪ Indeterminate- can produce more eggs than normal clutch, will continue to lay if eggs disappear – Visual, tactile, and hormonal influences cause them to stop