Avian Integument Flashcards
What are the 3 layers of avian epidermis?
Basal/germinative layer
Intermediate layer
Outer cornified layer
What is different about avian skin?
much thinner
effectively glandless
contains feather follicles
Describe the anatomy of the layers of avian dermis
Superficial layer - loosely arranged layers of collagen in interwoven bundles
Deep layer - contains fat, feather follicles, smooth muscles that control feather movement, blood vessels
Describe the anatomy of the the subcutaneous layer of avian skin
Formed mainly by loose connective tissue
Contains fat as a layer and discrete fat bodies (yellow deposits)
what is the clinical relevance of avian skin anatomy in surgery?
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
Describe the anatomy of the skin of avian legs and feet
Podotheca (non-feathered)
Scales are formed from raised heavily keratinised epidermis separated by fold of less keratinised tissue
What glands do birds have on their skin?
Uropygial glands
Glands of the ear canal
Pericloacal glands
Describe the location and anatomy of the uropygial gland in birds
bilobed gland
dorsal to cloaca at end of pygostyle
opens through caudally directed nipple
Describe the function of the uropygial gland
Why do some birds release a musty-mousy smell when stressed?
volatile fats emitted directly onto skin by rapidly lysing keratinocytes
What are patagia and what is their function?
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
Name the 4 patagia of the wings
Clinical relevance of patagia
Sites of loose skin - can be used for subcut injections
Frequent sites for self-induced ulcerative dermatitis (self-mutilation)
Why are patagia common sites for self mutilation in birds?
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
Describe the anatomy of the beak/rostrum of birds
Describe the histology of the beak/rostrum of birds
What is the bill tip organs function and what does it look like histologically?
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
What is an egg tooth?
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
Describe the location, appearance and anatomy of the cere of birds
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
Clinical relevance of the cere in birds
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)
Functions of the feather
Flight
Insulation ]
Waterproofing
Courtship displays
Defence
Aggressive territorial behaviour
What are pterylae and apteria
Pterylae - areas that contain feather tracts
Apteria - areas that do not contain feather tracts
Clinical relevance of apteria in birds
Used to assess skin quality
Easy access to jugular vein
Used for intradermal skin testing
Describe the anatomy and section of a feather
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
What is pith in a feather?
air-filled keratinised epithelial cells surrounded by keratinised outer cortex
Label this feather
What is plumulaceous and pennaceous in a feather vane?
Plumulaceous - soft/downy
Pennaceous - compact/closely nit
What is the function of barbules in a feather?
Complex interlocking hooking of the barbules creates a strong but light structure
What can observe under microscopy of moulted or plucked feathers?
What are the different types of feather?
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
Label these feathers
What are powder down feathers?
Describe the process of feather growth
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
How do feathers help maintain body temp?
Smooth muscle at the base of hair follicles increase or decrease the elevation of feathers from the skin
Label this feather follicle
What factors determine feather colours
Biochromes - colour pigments deposited at time of feather development
What types of biochromes are there?
Naturally occuring: food derived carotenoids (red,yellows)
Synthetically produced: melanins (browns, greens, black)
What causes are there for feather colour changes?
Natural (moult patterns)
Mutations
Disease
What are the types of feather colour mutations?
- genetic ability or inability to absorb, manufacture or deposit colour pigments
- alteration in barbule structure creating a different reflective or absorptive light pattern
Where does the normal ‘glow’ on birds feathers come from?
lipids derived from the keratinocytes
Which avian structures moult and how do they moult?
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
What influences moulting periods and patterns in birds?
At what rate can moulting occur?
What is proximal control of moulting in birds?
Hormonal control influenced by circannual rhythms of changing photoperiods and temp
Hormonal influences include:
- oestrogens
- progestergens
- thyroid
- catecholamines
- prolactin
How will a bird adjust its moult upon indadequate nutrition?
Delayed ore interrupted moult
reducing rate of feather production
sustaining production at the cost of other body functions
-> protracted moult and poor quality feathers
Why is good nutrition important for moulting in birds
Feathers have a high protein/keratin content
Renewing large amounts of feather tissue places a high metabolic and nutritional demand on the bird
What are ‘fret marks’/stress lines?
clear breaks in feather colour as a result of an interruption in feather growth and malformation of the feather barbs
What causes ‘fret marks’/stress lines in birds?
Poor nutrition
Environmental conditions
Disease
Drug stresses
