Avian Integument

Question 1

What are the 3 layers of avian epidermis?

Answer 1

Basal/germinative layer
Intermediate layer
Outer cornified layer

Question 2

What is different about avian skin?

Answer 2

much thinner
effectively glandless
contains feather follicles

Question 3

Describe the anatomy of the layers of avian dermis

Answer 3

Superficial layer - loosely arranged layers of collagen in interwoven bundles
Deep layer - contains fat, feather follicles, smooth muscles that control feather movement, blood vessels

Question 4

Describe the anatomy of the the subcutaneous layer of avian skin

Answer 4

Formed mainly by loose connective tissue
Contains fat as a layer and discrete fat bodies (yellow deposits)

Question 5

what is the clinical relevance of avian skin anatomy in surgery?

Answer 5

Limited amount of dermal tissue limits elasticity
Greatly reduces ability to ‘drag’ tissue to surgical sites for wound closure
Thin skin limits degree of tension that can be applied with sutures

Question 6

Describe the anatomy of the skin of avian legs and feet

Answer 6

Podotheca (non-feathered)
Scales are formed from raised heavily keratinised epidermis separated by fold of less keratinised tissue

Question 7

What glands do birds have on their skin?

Answer 7

Uropygial glands
Glands of the ear canal
Pericloacal glands

Question 8

Describe the location and anatomy of the uropygial gland in birds

Answer 8

bilobed gland
dorsal to cloaca at end of pygostyle
opens through caudally directed nipple

Question 9

Describe the function of the uropygial gland

Answer 9

Question 11

Why do some birds release a musty-mousy smell when stressed?

Answer 11

volatile fats emitted directly onto skin by rapidly lysing keratinocytes

Question 12

What are patagia and what is their function?

Answer 12

Skin reflected into flat, membrane-like structures where wings, legs, neck and tail join body - areas where movement of limbs occur
Responsible for wing stability and aid aerodynamics

Question 13

Name the 4 patagia of the wings

Answer 13

Question 14

Clinical relevance of patagia

Answer 14

Sites of loose skin - can be used for subcut injections
Frequent sites for self-induced ulcerative dermatitis (self-mutilation)

Question 15

Why are patagia common sites for self mutilation in birds?

Answer 15

Due to loss of stretch and flexion i these areas as a result of poor skin quality and resulting cracks and fissures which irritate the bird

Question 16

Describe the anatomy of the beak/rostrum of birds

Answer 16

Question 17

Describe the histology of the beak/rostrum of birds

Answer 17

Question 18

What is the bill tip organs function and what does it look like histologically?

Answer 18

Found on the beak
Sensitive to heat, cold, pressure and pain
High number of mechanoreceptors (Herbst corpuscles)
Histologically recognisable as papillae, originating from dermis ending at distal tip of beak

Question 19

What is an egg tooth?

Answer 19

Small pointed keratin eminence on the dorsal surface on the dorsal surface of the upper beak of recently hatched neonates
Used to break out of the egg
Falls off after a few days

Question 20

Describe the location, appearance and anatomy of the cere of birds

Answer 20

Base of upper beak
Composed of keratinzed skin
Nostrils located here in many species
The cere colour is influenced by diet and hormones:
- blue in male budgies due to testosterone
- brown in female budgies
- yellow in raptors due to carotenoids

Question 21

Clinical relevance of the cere in birds

Answer 21

Brown hypertrophy in male budgies - associated with change in sex hormone ration in testicular tumours
Hyperkeratosis and flaking of skin around cere in malnourished birds
Hyperkeratosis of the cere, beak and surrounding tissue associated with ‘honeycombing’ in ‘scaly face’ (knemidokoptics mites)

Question 22

Functions of the feather

Answer 22

Flight
Insulation ]
Waterproofing
Courtship displays
Defence
Aggressive territorial behaviour

Question 23

What are pterylae and apteria

Answer 23

Pterylae - areas that contain feather tracts
Apteria - areas that do not contain feather tracts

Question 24

Clinical relevance of apteria in birds

Answer 24

Used to assess skin quality
Easy access to jugular vein
Used for intradermal skin testing

Question 25

Describe the anatomy and section of a feather

Answer 25

Calamus - short, hollow, tubular, unpigmented end of mature feather - inserts into follicle
Rachis - long, solid, tubular extension of calamus - contains pith
Shaft - calamus + rachis
Vane/vexillum - portion that extends to either side of rachis - composed of barbs and associated structures - can be plumulaceous or pennaceous

Question 26

What is pith in a feather?

Answer 26

air-filled keratinised epithelial cells surrounded by keratinised outer cortex

Question 27

Label this feather

Answer 27

Question 28

What is plumulaceous and pennaceous in a feather vane?

Answer 28

Plumulaceous - soft/downy
Pennaceous - compact/closely nit

Question 29

What is the function of barbules in a feather?

Answer 29

Complex interlocking hooking of the barbules creates a strong but light structure

Question 30

What can observe under microscopy of moulted or plucked feathers?

Answer 30

Question 31

What are the different types of feather?

Answer 31

Coverts - small contour feather of the wing and tail
Remiges - large stiff feather of wing
Retrices - large flight feathers of the tail
Contour feather - predominant feather covering body

Question 32

Label these feathers

Answer 32

Question 33

What are powder down feathers?

Answer 33

Question 34

Describe the process of feather growth

Answer 34

Feather follicles formed from invaginations of the skin and closely fit the calamus
Follicle consists of epidermal and dermal cells
Dermis carries a hump of pulp to tip of calamus
Follicle is lined by living and cornified epidermal cells

Question 35

How do feathers help maintain body temp?

Answer 35

Smooth muscle at the base of hair follicles increase or decrease the elevation of feathers from the skin

Question 36

Label this feather follicle

Answer 36

Question 37

What factors determine feather colours

Answer 37

Biochromes - colour pigments deposited at time of feather development

Question 38

What types of biochromes are there?

Answer 38

Naturally occuring: food derived carotenoids (red,yellows)
Synthetically produced: melanins (browns, greens, black)

Question 39

What causes are there for feather colour changes?

Answer 39

Natural (moult patterns)
Mutations
Disease

Question 40

What are the types of feather colour mutations?

Answer 40

• genetic ability or inability to absorb, manufacture or deposit colour pigments
• alteration in barbule structure creating a different reflective or absorptive light pattern

Question 41

Where does the normal ‘glow’ on birds feathers come from?

Answer 41

lipids derived from the keratinocytes

Question 42

Which avian structures moult and how do they moult?

Answer 42

Soft keratin structures (e.g., scales, comb, wattle, cere) undergo constant moult and replacement
Feathers moult by the growth of a new feather causing shedding of old one

Question 43

What influences moulting periods and patterns in birds?

Answer 43

Question 44

At what rate can moulting occur?

Answer 44

Question 45

What is proximal control of moulting in birds?

Answer 45

Hormonal control influenced by circannual rhythms of changing photoperiods and temp
Hormonal influences include:
- oestrogens
- progestergens
- thyroid
- catecholamines
- prolactin

Question 46

How will a bird adjust its moult upon indadequate nutrition?

Answer 46

Delayed ore interrupted moult
reducing rate of feather production
sustaining production at the cost of other body functions
-> protracted moult and poor quality feathers

Question 47

Why is good nutrition important for moulting in birds

Answer 47

Feathers have a high protein/keratin content
Renewing large amounts of feather tissue places a high metabolic and nutritional demand on the bird

Question 48

What are ‘fret marks’/stress lines?

Answer 48

clear breaks in feather colour as a result of an interruption in feather growth and malformation of the feather barbs

Question 49

What causes ‘fret marks’/stress lines in birds?

Answer 49

Poor nutrition
Environmental conditions
Disease
Drug stresses