AvianAvianPg. 9-54Pg. 9-54

Avian AnatomyAvian Anatomy

Avian anatomyAvian anatomy, or the physiological structure of , or the physiological structure of bird’s bodies, shows many unique bird’s bodies, shows many unique adaptationsadaptations, , mostly aiding flight. mostly aiding flight.

Avian have evolved a light skeletal system and Avian have evolved a light skeletal system and light but powerful musculature which, along with light but powerful musculature which, along with circulatory and respiratory systems capable of circulatory and respiratory systems capable of very high metabolic rates and oxygen supply, very high metabolic rates and oxygen supply, permit the bird to fly. permit the bird to fly.

The development of a beak has led to evolution The development of a beak has led to evolution of a specially adapted digestive system. These of a specially adapted digestive system. These anatomical specializations have earned birds anatomical specializations have earned birds their own class in the vertebrate phylum.their own class in the vertebrate phylum.

TopographyTopography(External Anatomy) (External Anatomy)

TopographyTopography(External Anatomy) (External Anatomy)

IntegumentIntegument A bird’s body is covered by skin and its A bird’s body is covered by skin and its

derivates: the beak, claws, and feathers. These derivates: the beak, claws, and feathers. These structures cover and protect the internal organs structures cover and protect the internal organs and block the entrance of disease-causing and block the entrance of disease-causing organisms. organisms.

The skin of the birds consist of two layers; an The skin of the birds consist of two layers; an outer layer the outer layer the epidermisepidermis and the inner layer and the inner layer called called dermisdermis

The epidermis is relatively thin and consists of The epidermis is relatively thin and consists of flattened epithelial cells that produce keratinflattened epithelial cells that produce keratin

The dermis is thicker and consists of a fibrous The dermis is thicker and consists of a fibrous connective tissue. Smooth muscles in the dermis connective tissue. Smooth muscles in the dermis innervate feather follicles to help in the innervate feather follicles to help in the regulation of heat regulation of heat

IntegumentIntegument

The very thin skin is difficult to suture, The very thin skin is difficult to suture, usually requiring 4-0 or 5-0 sutureusually requiring 4-0 or 5-0 suture

The feet are an exception in that they The feet are an exception in that they usually have tick, prominent scales in the usually have tick, prominent scales in the non-feather regions to protect them from non-feather regions to protect them from trauma trauma

Birds bruise green because they lack Birds bruise green because they lack biliverdin reductase biliverdin reductase

GlandsGlands

Unlike mammals, birds don’t Unlike mammals, birds don’t posses sweat glandsposses sweat glands

The one major skin gland The one major skin gland that most birds posses is that most birds posses is called the called the uropygial glanduropygial gland oror preen gland located on the preen gland located on the dorsal surface at the upper dorsal surface at the upper base of the tail base of the tail

This gland secrets oily, fatty This gland secrets oily, fatty substance and birds use substance and birds use their beaks to spread around their beaks to spread around their body their body

This gland is lacking in some This gland is lacking in some parrots (amazons), ostriches parrots (amazons), ostriches and a few other species and a few other species

Beaks

• BeakOne derivate of bird’s skin is

its beak or bill. It consists of an upper and lower mandible and is covered with tough, horny keratin layer that grows continuously

Beaks vary in their hardness and flexibility depending on their function

ClawsClaws

Claws posses a horny Claws posses a horny sheath derived from sheath derived from specialized scales at the specialized scales at the end of each toe end of each toe

Like beaks, they also Like beaks, they also grow continuouslygrow continuously

Species differ in the type Species differ in the type of claws they posses of claws they posses based on heir perching based on heir perching habits and methods of habits and methods of procuring food procuring food

TalonsTalons

Feathers

Feathers are a unique feature of birds and they serve an amazing variety of functions including:

Flight Thermoregulation Swimming Protection Hygiene Water repellency Tactile sensation Support Camouflage Visual Communication

Birds have between 1000 and 25000 feathers

Feathers Feathers Feathers are made of

keratin. Keratin is produced in

the stratum corneum and stratum granulosum of the epidermis.

Types of Feathers Types of Feathers

Vaned or Contour Feathers

Down Semiplumes Filoplumes Bristles Powder Down

Contour feather Contour feather

Parts of a typical contour or vaned feather

remige = wing retrix =tail

Semiplume feather

Semiplumes are intermediate between contour feathers and down.

Their primary function is insulation.

Down feathers Down feathers Down feathers make Down feathers make

up the underplumage up the underplumage of a bird. They are of a bird. They are usually concealed usually concealed beneath the contour beneath the contour feathers, and their feathers, and their main function appears main function appears to be insulation against to be insulation against the cold weather the cold weather

FiloplumesFiloplumes

Filoplumes are Filoplumes are always situated always situated beside other beside other feathers. They are feathers. They are simple, hairlike simple, hairlike structures that grow structures that grow in circles around the in circles around the base of contour or base of contour or down feathers. They down feathers. They usually stand up like usually stand up like hairshairs

BristlesBristles

Not all species of birds Not all species of birds have bristle feathers. have bristle feathers. Bristles are Bristles are specialized feathers specialized feathers that are believed to that are believed to perform a tactile perform a tactile function. They have a function. They have a stiff, tapered rachis stiff, tapered rachis and few, if any barbs and few, if any barbs that appear only at the that appear only at the base of the feather base of the feather

Molt Molt Molting is the replacement of feathers and it

occurs once several times a year depending of the species • New feathers pushed out from below by replacement feathers produced in the feather follicle• Primary function is to replace worn feathers• Augmentation of breeding plumage is secondary• Molt imposes high energy demands• Song birds 2000-4000 feathers• Tundra Swan 25,000 feathers

Molt patterns reflect many selective pressures

.Climate • Migration • Social system • Food supplies • Predators • Competitors

Molt is an on-going, gradual process

SkeletonSkeleton

Modified for flightModified for flight Supports flight muscles (pectoral girdle, Supports flight muscles (pectoral girdle,

keel/sternum)keel/sternum) Withstands stress of flightWithstands stress of flight Wings – fewer, fused digitsWings – fewer, fused digits

Reduced massReduced mass Pneumatic bones- major bones hollow with struts, Pneumatic bones- major bones hollow with struts,

air spaces connected to respiratory systemair spaces connected to respiratory system Fused bones- adds rigidityFused bones- adds rigidity Lack teeth- lightweight beakLack teeth- lightweight beak

Skeletal System Skeletal System The bird skeleton is highly The bird skeleton is highly

adapted for flight. It is adapted for flight. It is extremely lightweight but extremely lightweight but strong enough to withstand strong enough to withstand the stresses of taking off, the stresses of taking off, flying, and landing. flying, and landing.

Birds also have more cervical Birds also have more cervical (neck) vertebrae than many (neck) vertebrae than many other animals; most have a other animals; most have a highly flexible neck highly flexible neck consisting of 8-25 vertebrae consisting of 8-25 vertebrae

One key adaptation is the One key adaptation is the fusing of bones into single fusing of bones into single ossifications ossifications

Pneumatic BonePneumatic Bone Not completely hollow, has strutsNot completely hollow, has struts Connected to respiratory system (air sacs and lungs)Connected to respiratory system (air sacs and lungs) Major bones of body pneumatic (femur, humerus and Major bones of body pneumatic (femur, humerus and

some vertebrae)some vertebrae) The number of hollow bones varies among species, The number of hollow bones varies among species,

though large gliding and soaring birds tend to have though large gliding and soaring birds tend to have the most the most

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Skeletal composition Skeletal composition

A bird's head (skull) is dominated A bird's head (skull) is dominated by the large eye sockets by the large eye sockets (orbits) which take up so much (orbits) which take up so much space that the braincase space that the braincase (cranium) is pushed to the (cranium) is pushed to the back back

The skull consists of five major The skull consists of five major bones: the frontal (top of bones: the frontal (top of head), parietal (back of head), head), parietal (back of head), premaxillary and nasal (top premaxillary and nasal (top beak), and the mandible beak), and the mandible (bottom beak). The skull of a (bottom beak). The skull of a normal bird usually weighs normal bird usually weighs about 1% of the birds total about 1% of the birds total bodyweight. bodyweight.

The chest consists of The chest consists of the furcula (wishbone) the furcula (wishbone) and coracoid (collar and coracoid (collar bone), which two bone), which two bones, together with bones, together with the scapula form the the scapula form the pectoral girdle. The pectoral girdle. The side of the chest is side of the chest is formed by the ribs, formed by the ribs, which meet at the which meet at the sternum (mid-line of the sternum (mid-line of the chest).chest).

The shoulder consists of the The shoulder consists of the scapula (shoulder blade), scapula (shoulder blade), coracoid (see The Chest), coracoid (see The Chest), and humerus (upper arm). and humerus (upper arm). The humerus joins the The humerus joins the radius and ulna (forearm) to radius and ulna (forearm) to form the elbow. The bones form the elbow. The bones in the wing are extremely in the wing are extremely light so that the bird can fly light so that the bird can fly more easily.more easily.

The hips consist of the The hips consist of the pelvis which includes three pelvis which includes three major bones: Illium (top of major bones: Illium (top of the hip), Ischium (sides of the hip), Ischium (sides of hip), and Pubis (front of the hip), and Pubis (front of the hip). These are fused into hip). These are fused into one (the innominate bone)..one (the innominate bone)..

Main Flight MusclesMain Flight Muscles Most birds have 175 different muscle, mainly controlling the

wings, skin and legs. The largest muscle in the bird are the pectorals or the breast

muscles which control the wings and make up about 15-25% of a flighted bird’s body weight.

The supracuracoideus and the pectoral together make up about 25-35% of the bird’s full body weight.

Avian Digestive Tract

• Beak– Excellent example of adaptation

to diet– Highly specialized beaks such

as hummingbirds, crossbills, and snail kite

– Prepare food for swallowing– Remove poorly digested

portions (e.g. seed, snail shells, bones)

Avian Digestive Tract

• Tongue – Has 3 primary roles– Collecting food – sticky tongue of woodpeckers, long thin tongue hummingbirds– Manipulating food in mouth• Muscular tongue of finches and parrots for handling seeds• Fish eating birds have stiff papilla• Filter feeding birds have bristles that mesh with lamellae on bill to form sieve– Swallowing – may have papilla to direct food items toward the back of the mouth

Avian Saliva

• Gray jays use saliva to

make balls of food to

store in trees

• Sticky tongue of

woodpeckers

• Swallow and swift

nests

• Bird-nest soup

Avian Digestive Tract

Digestive SystemDigestive System The crop functions to both

soften food and regulate its flow through the system by storing it temporarily. Members of the order Columbiformes, such as doves, produce a nutritious crop milk which is fed to their young by regurgitation

EsophagusThin walled, highlyfolded tube, largerthan in mammals

• Stomach – 2 parts• Thin walled sacks incarnivores• Proventriculus– Glandular, producesacids and enzymes• Ventriculus– Muscular part ofstomach (Gizzard)– Grinds food intosmall particles (teeth)– Large in herbivores

• Small Intestine –

Primary site digestion

and absorption

• Pancreatic secretions

– Bicarbonate for buffering

– Proteases

– Amylase

– Lipase

• Liver secretions

– Bile salts

• Ceca – blind pouchesat junction of smalland large intestine• Contain microbes– Fermentation– Vitamins– Nitrogen metabolism– Water and electrolytes• Large intestine– Absorbs water andstores feces• Cloaca

cloacacloaca is the is the posterior opening that posterior opening that serves as the only serves as the only such opening for the such opening for the intestinal, , urinary, and , and (usually) (usually) genital tracts of certain animal of certain animal species species

Cloacal StructureCloacal Structure

Oviduct

Female Reproductive TractFemale Reproductive Tract Ovary Ovary Most female birds Most female birds

have one functionally have one functionally ovary (on the left)ovary (on the left)

InfundibulumInfundibulum - site of - site of fertilizationfertilization

MagnumMagnum - albumin - albumin additionaddition

IsthmusIsthmus - membranes - membranes UterusUterus - shell gland - shell gland VaginaVagina - transport to - transport to

exteriorexterior Sperm storage occurs at Sperm storage occurs at

various sites in tract in various sites in tract in some speciessome species

Reproductive cont..Reproductive cont.. Males have two testis and a Males have two testis and a

rudimentary fold of tissue rudimentary fold of tissue called a phallus instead of a called a phallus instead of a penispenis

Most bird species rub their Most bird species rub their cloacal areas together to cloacal areas together to transfer the male's sperm but transfer the male's sperm but ostriches, rheas, strokes, ostriches, rheas, strokes, flamingos, ducks and a few flamingos, ducks and a few other families actually have other families actually have an erectile grooved penis on an erectile grooved penis on the back wall of the cloaca to the back wall of the cloaca to transfer sperm.transfer sperm.

Reproductive activityReproductive activity The small species, such as cockatiels, The small species, such as cockatiels,

can be reproductively active as early can be reproductively active as early as 6 months of ageas 6 months of age

Larger species, such as macaws, may Larger species, such as macaws, may not be reproductively active until over not be reproductively active until over 3 years of age3 years of age

Cockatiels are prolific breeders, and Cockatiels are prolific breeders, and females can lay many eggs even in the females can lay many eggs even in the absence of a male birdabsence of a male bird

Commonly, egg-laying female Commonly, egg-laying female cockatiels on a seed diet become egg cockatiels on a seed diet become egg bound, requiring ER medical bound, requiring ER medical assistanceassistance

IncubationIncubation Typically, an egg is formed in the uterus over 24 hoursTypically, an egg is formed in the uterus over 24 hours The incubation period (from laying to hatching) for The incubation period (from laying to hatching) for

budgie and cockatiel eggs is 18 to 21 days, respectively, budgie and cockatiel eggs is 18 to 21 days, respectively, whereas for the African grey parrots, Amazon parrots, whereas for the African grey parrots, Amazon parrots, and macaws it is app. 26 daysand macaws it is app. 26 days

Some aviculturists allow the parent birds to incubate the Some aviculturists allow the parent birds to incubate the eggs and then remove the neonates from the nest at 10 eggs and then remove the neonates from the nest at 10 days of age to be hand-fed, as is commonly practiced w/ days of age to be hand-fed, as is commonly practiced w/ parrotsparrots

Others will remove the eggs immediately after being laid Others will remove the eggs immediately after being laid and place them in an incubator, then a hatcher, and then and place them in an incubator, then a hatcher, and then hand-feed the neonateshand-feed the neonates

Respiratory SystemRespiratory System They lack a diaphragm, They lack a diaphragm,

have nonexpandable lungs have nonexpandable lungs and a system of air sacs and a system of air sacs which extend into many of which extend into many of their bones. their bones.

Vocalization is by means of Vocalization is by means of a syrinx, not a larynx as in a syrinx, not a larynx as in mammals mammals

Unidirectional air flowUnidirectional air flow System of air sacsSystem of air sacs

Average of 9Average of 9 Chickens 8Chickens 8 Serve variety of functionsServe variety of functions

The nostrils or The nostrils or naresnares are are usually located at the base of usually located at the base of the beak. In psittacines the beak. In psittacines (parrots) they are located (parrots) they are located within the area of the cere within the area of the cere

The nasal cavity is divided The nasal cavity is divided into a right and left side by a into a right and left side by a nasal septum. This septum is nasal septum. This septum is composed of cartilage and composed of cartilage and bone bone

A large sinus known as the A large sinus known as the infraorbital sinus, surrounds infraorbital sinus, surrounds the eye and extends into the the eye and extends into the upper and lower beak upper and lower beak

The larynx is at the entrance The larynx is at the entrance of the trachea. The opening of the trachea. The opening of the larynx is the glottis. of the larynx is the glottis. Birds differ from mammals in Birds differ from mammals in that the larynx does not have that the larynx does not have vocal chords and therefore is vocal chords and therefore is not involved in voice not involved in voice production. production.

The trachea is formed by a The trachea is formed by a series of ring-shaped series of ring-shaped cartilages, which are cartilages, which are completely closed in birds* completely closed in birds*

The trachea bifurcates The trachea bifurcates (divides) after entering the (divides) after entering the thoracic cavity. The syrinx or thoracic cavity. The syrinx or voice box is located at this voice box is located at this bifurcation. bifurcation.

*easy to intubate*easy to intubate

The nine air sacs also act The nine air sacs also act as a cooling system since as a cooling system since birds do not have sweat birds do not have sweat glands. glands.

Anatomically, their lungs Anatomically, their lungs are connected to large are connected to large thin-walled thin-walled air sacsair sacs, , which appear to function which appear to function sort of like bellows rather sort of like bellows rather than like lungs, such that than like lungs, such that they have a minimal they have a minimal blood supply and they blood supply and they are not involved in gas are not involved in gas exchange. exchange.

Oxygen exchange in the Oxygen exchange in the bird occurs bird occurs on inspiration on inspiration and expirationand expiration

Renal SystemRenal System Mammalian and reptilian type nephrons are present, Mammalian and reptilian type nephrons are present,

therefore birds produce liquid urine and pasty white therefore birds produce liquid urine and pasty white uratesurates

Note that kidney in birds is not measured by BUN Note that kidney in birds is not measured by BUN and creatinine levels, but by levels of uric acidand creatinine levels, but by levels of uric acid

Cardiovascular System Cardiovascular System Birds have very efficient cardiovascular systemsBirds have very efficient cardiovascular systems that that

permit them to meet the metabolic demands of flight (and permit them to meet the metabolic demands of flight (and running, swimming, or diving). running, swimming, or diving).

The cardiovascular system not only delivers oxygen to The cardiovascular system not only delivers oxygen to body cells (and removes metabolic wastes) but also plays body cells (and removes metabolic wastes) but also plays an important role in maintaining a bird's body temperature.an important role in maintaining a bird's body temperature.

The avian circulatory system consists of a heart plus The avian circulatory system consists of a heart plus vessels that transport: vessels that transport: -nutrients -nutrients -oxygen and carbon dioxide -oxygen and carbon dioxide -waste products -waste products -hormones -hormones -heat-heat

Birds, like mammals, have Birds, like mammals, have a 4-chambered heart (2 a 4-chambered heart (2 atria & 2 ventricles), with atria & 2 ventricles), with complete separation of complete separation of oxygenated and de-oxygenated and de-oxygenated blood.oxygenated blood.

The right ventricle pumps The right ventricle pumps blood to the lungs, while the blood to the lungs, while the left ventricle pumps blood to left ventricle pumps blood to the rest of the body. the rest of the body.

Avian hearts also tend to pump more blood per unit time Avian hearts also tend to pump more blood per unit time than mammalian hearts. Cardiac output is influenced by than mammalian hearts. Cardiac output is influenced by

both heart rate (beats per minute) and stroke volume both heart rate (beats per minute) and stroke volume (blood pumped with each beat). The renal-portal system (blood pumped with each beat). The renal-portal system (that system in which blood from caudal half of body can (that system in which blood from caudal half of body can

go to the kidney before going go the heart) exists in these go to the kidney before going go the heart) exists in these patientspatients