Vet Tech A&P - Avian Integument

The skin of birds consists of how many layers? Name them.

Two. Epidermis and dermis.

Describe the epidermis.

thin, consists of flattened epithelial producing keratin

What is keratin? Why is it important to birds?

tough, fibrous protein.
necessary for production of scales, feathers, and the outer sheath of beaks and claws

What is the inner layer of skin? What is it made of?

dermis
tough, fibrous connective tissue

What role does the dermis play in avians?

stores fat for nutrition, insulates, supplies pathway for nerves, blood vessels, and muscles to reach the epidermis

What role do smooth muscles in the dermis play in avians?

innervate feather follicles to help regulate heat

What are depressor muscles for?

press the feathers against the body to promote heat loss; in hot weather

What are erector muscles for?

to elevate the body feathers to trap warm air near the body; in cold weather or during illness

Do birds have sweat glands? Why or why not?

No. They would not be effective since feathers cover such a large portion of the body.

What is the major skin gland?

uropygial gland or preen gland

Where is the preen gland?

dorsal surface at upper base of tail

What role does the uropygial gland play in preening?

preening stimulates the gland to secrete an oily, fatty substance. Using its beak, a bird spreads this throughout its feathers to clean and waterproof them

Do all birds have uropygial glands?

No. Some parrots, ostriches, and other species do not.

What kinds of birds might have a larger uropygial gland?

acquatic species; waterfowl, osprey

Describe the anatomy of a beak or bill.

Upper and lower mandible, covered with a tough, horny keratin layer; continuously growing.

What do various birds use their beaks for? Specify species.

Parrots: crack seeds and nuts
Hawks: tear into bite-sized pieces
Herons: capture food
Also, preening, picking up/holding, climbing, protection

Describe the anatomy of claws.

horny sheath of specialized scales at the end of each toe; grow continuously

What are claws used for? Specify species.

Chickens: short, sharp for scratching ground
Prey birds: long, sharp, rounded talons to catch and kill
Vultures: short, blunt
Woodpeckers: strong, curved for gripping

What are the derivatives of a bird's skin? What is their purpose?

The skin gives rise to beaks, claws, and feathers.
It covers and protects internal organs, and blocks the entrance of disease-causing organisms.

What is feaking?

rubbing the beak on a hard surface to clean it and maintain its length and shape

What happens if a bird is unable to feak or its beak is not coped?

It grows too long causing difficulty in eating, also causing large cracks and chips. Can cause permanent damage to growth plate.

Where is the beaks growth plate located?

near the cere

What happens if claws are not coped?

Grow too long and sharp causing uneven weight bearing on the footpads or puncture the bottom of a foot. Pad abrasions, blisters, swelling, abscess formation, osteomyelitis. aka bumblefoot

Do beaks and nails contain blood and nerves?

Yes

What can be done to achieve hemostasis after a bleed?

topical cauterizing agents; silver-nitrate or Quick-Stop

Feathers are made of ___ and originate from ___.

protein; a follicle

What are the functions of feathers?

flight, protect skin from trauma, rain, radiation from sun, thermoregulation, camouflage, communication i.e. courtship, defense, recognition

How many types of feathers are there? Name them.

Six. Contour, semiplume, down, filoplume, bristle, powder down

What is the inferior umbilicus?

The tiny opening at the base of the feather, where it inserts into the skin. Blood vessels pass through.

What is the superior umbilicus?

Tiny opening on the feather shaft where the webbed part of the feather begins.

In certain species, the superior umbilicus gives rise to ___. Why?

an afterfeather. It is thought to provide additional insulation.

What is a calamus? Where is it?

aka quill; round, hollow, semitransparent portion of the feather. Extends from inferior to superior umbilicus.

What is a rachis?

main feather shaft

What and where is the vane?

flattened, web-like part of a feather; each side of the rachis.

Describe vane anatomy?

Numerous slender, closely spaced barbs, giving rise to barbules with rolled edges and tiny hooklets aka hamuli. Hamuli interlock barb with adjacent barb = tight, flexible web

What is the purpose of a more loose contour feather weave in owls?

fewer barbules; softer feel and allows better air flow, creating silent flight

Where are contour feathers located and what is their purpose?

most visible, give bird its shape; flight feathers of the wing and tail

What are remiges?

flight feathers in the wing

What are retrices?

tail feathers

What are auriculars?

small contour feathers; around external ear opening; improve hearing ability. Especially numerous in parrots, hawks, and owls.

How are contour feathers controlled?

moved by muscles attached to the walls of the follicles

Describe semiplume feather anatomy.

possess main rachis with barbs (no barbules or hooklets)

Where are semiplume feathers found?

under contour feathers, especially sides of abdomen and along neck and back

What is the purpose of semiplume feathers?

provide insulation and flexibility for movement of contour feathers; helps buoyancy of water birds

Describe the anatomy of down feathers.

soft, fluffy, lack a true shaft or barbules and hooklets on their barbs

Where are down feathers found and what is their primary function?

next to the skin under contour feathers; insulation

Describe the anatomy of filoplume feathers.

bare shaft that lacks barbs on the majority of its length, except at the tip

Where are filoplume feathers located?

nape and upper back near contour feathers

What is the role filoplume feathers play in feather movement?

follicles contain sensitive nerve endings that may play a sensory role in controlling feather movement. Pressure and vibration receptors in the skin receive messages re: contour feathers

What are bristles and what are they for?

modified contour feathers with a stiff rachis and few barbs at the base; sense of touch

Where are bristles found?

Crows, ravens, woodpeckers: around nostrils
Owls: around mouth, toes
Other species: around eyes

Discuss powder down feathers.

unusual; never stop growing at the base, disintegrate at tip, creating waxy powder that spreads throughout the plumage to clean and waterproof

Where are powder down feathers usually found?

breast, belly, back

Birds without a uropygial gland do or not have an abundance of powder down feathers?

do

Where do feathers originate from?

specific tracts: pterylae

What are the bare areas of skin called?

apteria

If the birds entire body is not covered by feathers, how do they have a fully feathered look?

feathers in the tracts overlap one another

How many feathers tracts are there? Name them.

8; capital, humeral, alar, central (ventral), spinal, femoral, crural, caudal

What kind of damage are feathers and wings subject to?

feather mites chew and consume vanes, creating weak points; daily wear and tear; during growth, stress can interrupt blood flow

What is a fault bar?

result of interrupted blood flow to a feather during growth; weakened area on the vane (barbs lack barbules)

How can diet effect feather development?

insufficient supply or deficiency in nutrients can severely effect growth and plumage

What is molting?

feather replacement

How much of a birds body weight consists of feathers?

4 - 12%

How often does molting occur?

dependent on species; once to several times per year

In most species, feather replacement is ___.

symmetrical; to allow continued flight

Which type of bird molts all their flight feathers at once? When? What about their food source?

some waterfowl; after breeding; graze on land or in water

When is the major annual molt for most North American species? Why?

end of breeding, beginning of migration. Abundant food sources so energy can be focused on regrowth

How and where do new feathers develop?

from papillae in dermis layer of skin; feather tracts. Papillae contain germ cells with genetic info.

How are papillae germ cells activated for regrowth?

physiological and environmental factors; increase in day length stimulates pituitary and thyroid glands (also possibly sex hormones)

How does the process of molting occur?

new developing feather pushes old one out; emerges from skin covered by periderm

What is periderm?

epidermal covering of newly developed feather

What becomes of the periderm after it emerges?

during preening bird gently removes periderm (looks like small white flakes in plumage)

How is the newly developed feather nourished?

dermal blood vessels

When does new feather nourishment cease?

after feather is fully grown, blood dries up, rachis pinched closed under skin

What is a blood feather?

developing new feather; blood can be seen in the proximal part of the feather shaft during entire growth phase.

What happens if blood feathers are damaged?

bleeding, normal development prevented until another molting occurs

List the three major functions of feathers.

protection, flight, insulation

What type of feathers are the flight and tail feathers? Describe their microstructure.

contour; inferior umbilicus (opening at base, blood supply), superior umbilicus (webbing begins), calamus (round, hollow, btwn inf./sup. umb.), rachis (main feather shaft), vane (flattened, weblike, with barbs)

Define a fault bar. What causes it?

interruption of blood flow to developing feather caused by stress; weakened area. Usually stress re: food supply

How do the wing and tail feathers differ between predatory and prey bird species?

Some predatory birds have fewer barbules to create silent flight; auriculars to improve hearing

What is feather-picking disorder?

similar to trichotilomania

What causes feather-picking disorder?

pathological: toxins, bacteria, virus, fungi, parasites, malnutrition
psychological: environmental change, diet, human exposure, boredom, sexual frustration, anxiety, new pet exposure

What is the purpose of wing clipping?

to clip flight feathers to prevent a bird from gaining lift but to still allow it to glide safely; prevent accidental escape