416
edits
Changes
Feather - Anatomy & Physiology (view source)
Revision as of 09:09, 14 July 2008
, 09:09, 14 July 2008→Feather growth
===Feather growth===
===Feather growth===
Feathers arise from feather follicles. These are formes by invaginations of the skin and closely fit the calamus. The feather follicle is analogous with the [[Hair - Anatomy & Physiology#Hair Types|hair follicle]] in mammals. As in mammals, the follicle consists of epidermal and dermal cells and is lined with living and cornified epidermal cells. At the umbilicus of the calamus, the dermis carries a hump of pulp into the tip of the calamus. The follicular wall has an abundant supply of sensory nerve fibres, and the papillae, pulp and feather muscles are also well innervated. Smooth muscles at the base of the feather follicles help maintain body temperature by increasing or decreasing the elevation of the feathers from the skin. [[Skin - Anatomy & Physiology#Beak|Herbst's corpuscles]] at the base of the feather follicles are believed to detect subtle ground vibrations and changes in air current.
Feathers arise from feather follicles. These are formes by invaginations of the skin and closely fit the calamus. The feather follicle is analogous with the [[Hair - Anatomy & Physiology#Hair Types|hair follicle]] in mammals. As in mammals, the follicle consists of epidermal and dermal cells and is lined with living and cornified epidermal cells. At the umbilicus of the calamus, the dermis carries a hump of pulp into the tip of the calamus. The follicular wall has an abundant supply of sensory nerve fibres, and the papillae, pulp and feather muscles are also well innervated. Smooth muscles at the base of the feather follicles help maintain body temperature by increasing or decreasing the elevation of the feathers from the skin. [[Skin - Anatomy & Physiology#Beak|Herbst's corpuscles]] at the base of the feather follicles are believed to detect subtle ground vibrations and changes in air current.
===Feather colour===
Feather colour is determined by two factors:
*'''Biochromes''': Colour pigments that are deposited at the time of feather development. These can be naturally occurring, e.g. food derived carotenoids in unaltered or modifed states, or synthetically produced, e.g. melanins (browns, greens and black).
The colour can have structural properties also:
These structural features of the feather can be inherent in the development of the feather. They can also be induced by materials that are placed on the feathers after development, that alter the absorption or reflection of light.
If a feather reflects all light, it appears white; if it absorbs all wavelengths, it appears black. The capacity of the barbs and barbules to scatter and reflect varying wavelengths of light causes and irridescent glow of the feathers. Blue colours are created by the barbs interacting to reflect blue light, while allowing other wavelenghts of light to be absorbed by darker melanin granules. Green colours may be created by pigments, or more commonly, through a combination of blue and yellow pigments.