Anatomy Physiology and Clinical Implications of the Avian Integument

Question 1

• How does the avian skin differ from that of mammals?

Answer 1

Much thinner, effectively glandless and contains feather follicles

Question 2

• What are the three layers of the epidermis?

Answer 2

The basal (germinative) layer, intermediate layer, outer cornified layer

Question 3

• What are the two layers of the dermis?

Answer 3

Superficial layer & deep layer (contains feather follicles and smooth muscle)

Question 4

• What is podotheca?

Answer 4

The non-feathered areas of the legs and feet

Question 5

• What are scales formed from?

Answer 5

Heavily keratinised epidermis separated by folds of less keratinised tissue

Question 6

• What glands are present in avian skin?

Answer 6

Uropygial gland, glands of the ear canal, Pericloacal glands, (keratinocytes)

Question 7

• What is the function of the uropygial gland?

Answer 7

Involved in maintaining feather condition and secretions spread by preening – waterproofing function, secretes pro-vitamin D, oil affects light absorption and feather colouring

Question 8

• Why might keratinocytes be described as glands?

Answer 8

Developing dermal cells (keratinocytes) undergo metamorphosis from cuboidal or squamous nature, lose organelles, produce lipids and keratin and dehydrate and lyses – lipid production of keratinocytes makes the entire skin an oil-producing gland

Question 9

• What are the four patagia of the wing?

Answer 9

Propatagium, postpatagium, metapatagium, alular patagium

Question 10

• What is rhamphotheca?

Answer 10

Horny covering of the maxilla and mandible – forms the beak

Question 11

• Why is the beak very sensitive to heat, cold, pressure and pain?

Answer 11

High number of mechanoreceptors (Herbst corpuscles)

Question 12

• What is the cere?

Answer 12

Keratinised skin situated at the base of the upper beak – colour is influenced by diet and hormones

Question 13

• What is the difference between pterylae & apteria?

Answer 13

Pterylae – areas that contain feather tracts, apteria – areas that do not have feather tracts

Question 14

• What are the common terms used to describe portions of the feather?

Answer 14

Calamus (short, hollow, tubular, in the feather follicle), rachis (extension of the calamus above the skin), shaft (calamus & rachis) & vane or vexillum (the portion of the feather that extends to either side of the rachis)

Question 15

• What does the quality of the bars and barbules of the feather give an indication of?

Answer 15

Nutritional status of the bird

Question 16

• List some of the common types of feather

Answer 16

Contour feathers – predominant feather type
Convert feathers – small contour feathers of the wing and tail
Remiges feathers – large stiff feathers of the wing
Retrices feathers – large flight feathers of the tail
Specialised adapted feathers – semiplumes, hypopnea, filiplumes & bristles
Down feathers – adult, natal & powder down

Question 17

• What are powder down feathers?

Answer 17

Specialised down feathers that disintegrate and produce keratin that is spread through the features during preening

Question 18

• How does a feather follicle form?

Answer 18

Invagination of the skin, consists of epidermal and dermal cells, follicular wall has an abundant supply of sensory nerve fibres and the papillae, pulp and feather muscles are also well innervated

Question 19

• Describe the process of moulting

Answer 19

Soft keratin structures undergo constant moult and replacement, feathers moult by the growth of a new feather causing the shedding of an old one
Moult can be gradual, dramatic or continual

Question 20

• What hormonal influences have been identified as affecting the moult?

Answer 20

Oestrogens, progestogens, thyroid, catecholamines, prolactin

Question 21

• What are the effects of inadequate nutrition on the moult?

Answer 21

Delays or interrupts the moult, reduces the rate of feather production, sustains production at the cost of other body functions

Question 22

• What are stress lines?

Answer 22

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

Question 23

• What is feather colour determined by?

Answer 23

Biochromes & structural properties

Question 24

• What are the two basic types of colour mutations?

Answer 24

The genetic ability or inability to absorb, manufacture or deposit colour pigments & an alteration in feather structure creating a different reflecting or absorptive light pattern