Avian Anatomy and Physiology

Christine Fiorello, DVM, PhD, Dipl. ACZM

Some slides from Heather Wilson, DVM, Dipl. ABVP Avian

Integument 2 layers: Dermis and epidermisEpidermis thin except for certain areasKeratinization produces special structures: beak, nails, scales, feathersLacks glands

Feathers-7 typesContour

wing & tail (flight)

SemiplumeDown

fluffy, no barbules

Bristle“eyelashes”

Powder downHypopennaFiloplume

Uropygial Gland“Preen gland”Bilobed holocrine glandConditions feathersNot all species have one

Purpose of Feathers

FlightCourtshipDefenseInsulationWaterproofing

Contour Feathers

Rows (pterylae) in most speciesApteryla=feather-less tractsRemiges=Wing flight feathersRetrices=Tail flight feathers

Primaries attach to metacarpalsSecondaries attach to ulna

WaterproofingPreen gland secretions are not necessaryInterlocking of feather barbules creates watertight barrier

Musculoskeletal System

Synsacrum

Notarium

Coccygeal

Avian wingsUnique structureFlight feathers attached to ulnaand metacarpalsUlna > radius Bat

Pterodactyl

Superman

Pectoral girdle

Clinical skeletal anatomySpinal fractures at juncture of notarium and synsacrumSee with birds who flew into a window

FracturesBones are more brittle compared to mammalsBones heal more rapidly• 4 weeks

Fibrocartilagenous healing first• may not be visible

radiographically

Pectoral Muscle

Highly vascularized muscleIM injections here are absorbed rapidlyNonflighted birds have soft, “flabby” pectoral muscles

Lower limbsFemurTibiotarsusTarsometatarsus

“Hock” is tibiotarsal-tarsometatarsal joint

Each digit has +1 phalanx

Digit one has 2 phalangesDigit two has 3, etc

Parrots are zygodactylus

Digits 1 & 4 face backDigits 2 & 3 face forward

Feet

Cardiovascular system4 chambered heartEncircled by liverRight jugular vein larger than left (which may be absent)

Lymphatic SystemNo lymph nodesLymph vessels follow veinsLymph plexuses (rete)Bursa of Fabricius

B-cells

KidneysAdhered to dorsal body wallRetroperitoneal3 lobesExcrete uric acid and some urine

Renal Portal System

Nervous SystemBrain: 3 meniges & 12 CN as in mammalsIn contrast, birds have no neocortexSurface of cerebrum almost smoothOlfactory bulb relatively small

Mammal

Bird

Bird Brain

EyesMost birds have excellent visionMore cones than rods (in general)No blind spot (no optic disk)

Pecten, unique to birds, provides nutrientsIris contains striated muscle--can’t use atropine to dilate

Need curariform drugs

Coelomic Cavities16 separate cavities within body8 air sacs5 peritoneal2 pleural1 pericardial

Upper Respiratory Tract

NaresCere

OperculumSinusesConchaeChoanaOropharynx

Upper respiratory tract

choana

Nasal cavityCommunicates with oral cavity

Choanaexceptions

No soft palate

Respiratory anatomyTrachea

Relatively largeGlottis at base of tongueComplete rings

No diaphragmSyrinx (no larynx)

Clinical anatomyChoanal swabsChlamydiophila testingBacterial culture

Sinusitis

Complete tracheal ringsUse extreme care with

intubated birds

Infraorbital sinusAccess: between medial canthus and oral commissure

Diagnositc samplesTherapeutic flushing

Easier than trephining a horse!

Infraorbital sinus

Air sacsNo gas exchange9 air sacs in parrotsCan ventilate via air sac cannulaPoorly vascularized

Bad place for infectionAir sacculitis difficult to treat

Air sacsPneumatic bones

humerus, femurDon’t put intraosseous catheters here

Must move sternum to breathe

Don’t smush little birds during restraintDon’t lean on chests of anesthetized birds

Avian lungsUnidirectional air flow

Extremely efficient compared to mammalsGas exchange occurs in air capillaries of parabronchiRigid lung

GI Tract

GI Tract

Oral cavityRamphotheca-upper sheathGnathotheca-lower sheath

Cervical Esophagus

Thoracic Esophagus

No gallbladder in parrots or pigeons

Upper GI TractCrop not present in all speciesProventriculus is glandular stomachVentriculus (gizzard) is muscular

Lined with koilin

IntestinesPaired cecae mark the junction between small and large intestineDuodenum, jejunum, ileum as in mammals

Cloaca and Vent

GI and Urogenital tracts end in cloacaCoprodeumUrodeumProctodeumVent is opening into cloaca

C

U

P

Male Reproductive

Tract 2 testisRudimentary phallus (may or may not be intromittant)Parrots non-intromittant

Iliac

Female Reproductive

TractLeft ovary InfundibulumMagnumIsthmusUterus (shell gland or oviduct)

Adrenal GlandsPairedMedial and cranial to kidneys and gonadsFunction similar to mammalian adrenals

Thyroid,Parathyroid &

Thymus