Keratin Bonds

keratin bonds

Feather   by hi joiney

Structure and characteristics Parts of a feather 1 Vane 2 Rachis 3 Barb 4 Afterfeather 5 Hollow shaft calamus Featherstructure of a Blue and yellow Macaw Feathers are among the most complex integumentary appendages found in vertebrates and are formed in tiny follicles in the epidermis or outer skin layer that produce Keratin proteins The Keratins in feathers beaks and claws and the claws scales and shells of reptiles are composed of protein strands hydrogen bonded into pleated sheets which are then further twisted and crosslinked by disulfide bridges into structures even tougher than the keratins of mammalian hair horns and hoof The exact signals that induce the growth of feathers on the skin are not known but it has been found that the transcription factor cDermo 1 induces the growth of feathers on skin and scales on the leg Feather microstructure showing interlocking Classification See also Flight feather There are two basic types of feather vaned feathers which cover the exterior of the body and down feathers which are underneath the vaned feathers The pennaceous feathers are vaned feathers Also called contour feathers pennaceous feathers arise from tracts and cover the whole body A third rarer type of feathers filoplumes is hairlike and if present in a bird grows along the fluffy down feathers In some passerines filoplumes arise exposed beyond the contour feathers on the neck The remiges or flight feathers of the wing and rectrices the flight feathers of the tail are the most important feathers for flight A typical vaned feather features a main shaft called the rachis Fused to the rachis are a series of branches or barbs the barbs themselves are also branched and form the barbules These barbules have minute hooks called barbicels for cross attachment Down feathers are fluffy because they lack barbicels so the barbules float free of each other allowing the down to trap much air and provide excellent thermal insulation At the base of the feather the rachis expands to form the hollow tubular calamus or quill which inserts into a follicle in the skin The basal part of the calamus is without vanes This part is embedded within the skin follicle and has an opening at the base proximal umbilicus and a small opening on the side distal umbilicus Hatchling birds of some species have a special kind of natal down neossoptiles and these are pushed out when the normal feathers teleoptiles emerge Flight feathers are stiffened so as to work against the air in the downstroke but yield in other directions It is noted that the pattern of orientation of keratin fibers in the feathers of flying birds differs from that in flightless birds The fibers are better aligned in the middle of the feather and less aligned towards the tips Functions Feathers insulate birds from water and cold temperatures They may also be plucked to line the nest and provide insulation to the eggs and young The individual feathers in the wings and tail play important roles in controlling flight Some species have a crest of feathers on their heads Although feathers are light a bird s plumage weighs two or three times more than its skeleton since many bones are hollow and contain air sacs Color patterns serve as camouflage against predators for birds in their habitats and by predators looking for a meal As with fish the top and bottom colors may be different to provide camouflage during flight Striking differences in feather patterns and colors are part of the sexual dimorphism of many bird species and are particularly important in selection of mating pairs In some cases there are differences in the UV reflectivity of feathers across sexes even though no differences in color are noted in the visible range The wing feathers of male Club winged Manakins Machaeropterus deliciosus have special structures that are used to produce sounds by stridulation A contour feather from a Guinea fowl Some birds have a supply of powder down feathers which grow continuously with small particles regularly breaking off from the ends of the barbules These particles produce a powder that sifts through the feathers on the bird s body and acts as a waterproofing agent and a feather conditioner Powder down has evolved independently in several taxa and can be found in down as well as pennaceous feathers They may be scattered in plumage in the pigeons and parrots or in localized patches on the breast belly or flanks as in herons and frogmouths Herons use their bill to break the feathers and to spread them while cockatoos may use their head as a powder puff to apply the powder Waterproofing can be lost by exposure to emulsifying agents due to human pollution Feathers can become waterlogged and birds may sink It is also very difficult to clean and rescue birds whose feathers have been fouled by oil spills The feathers of cormorants soak up water and help in reducing buoyancy and thereby allowing the birds to swim submerged Rictal bristles of a White cheeked Barbet Bristles are stiff tapering feathers with a large rachis but few barbs Rictal bristles are bristles found around the eyes and bill They may serve a similar purpose to eyelashes and vibrissae in mammals It has been suggested that they may aid insectivorous birds in prey capture or that it may have sensory functions however there is no clear evidence In one study Willow Flycatchers Empidonax traillii and they were found to catch insects equally well before and after removal of the rictal bristles Grebes are peculiar in their habit of ingesting their own feathers and also feeding them to their young Observations on the diet and feather eating frequency suggest that ingesting feathers particularly down from their flanks aids in forming easily ejectable pellets along with their diet of fish Distribution Feather tracts or pterylae and their naming Contour feathers are not uniformly distributed on the skin of the bird except in some groups such as the Penguins ratites and screamers In most birds the feathers grow from specific tracts of skin called pterylae while there are regions which are free of feathers called apterylae Filoplumes and down may arise from the apteriae regions between the pterylae The arrangement of these feather tracts pterylosis or pterylography varies across bird families and has been used in the past as a means for determining the evolutionary relationships of bird families Coloration The colors of feathers are produced by the presence of pigments such as melanins browns blacks greys carotenoids reds yellows orange psittacofulvins unique red pigments found in some parrots and porphyrins such as the green turacoverdin of Turacos or more often by feather structure Structural coloration is involved in the production of most greens blues iridescent colors ultraviolet reflectance and in the enhancement of pigmentary colors Structural iridescence in feathers has been reported in fossil feathers dating back 40 million years The blues and greens of many parrots are produced by constructive interference of light reflecting from different layers of the structures in feathers in addition to the yellow carotenoid pigments Melanin is often involved in the absorption of some of the light in these feathers The specific feather structure involved is sometimes called the Dyck texture A feather with no pigment Albinism is caused by the lack of pigment in some or all of a bird s feathers In some birds the feather colors may be created or altered by uropygial gland secretions The yellow bill colors of many hornbills are produced by preen gland secretions Other differences that may only be visible in the ultraviolet region have been suggested but studies have failed to find evidence Uropygial oil secretion may also have an inhibitory effect on feather bacteria A bird s feathers undergo wear and tear and are replaced periodically during its life through molting New feathers are formed through the same follicle from which the old ones were fledged The presence of melanin in feathers increases their resistance to abrasion One study notes that melanin based feathers were observed to degrade more quickly under bacterial action even compared to unpigmented feathers from the same species than those unpigmented or with carotenoid pigments However another study the same year compared the action of bacteria on pigmentations of two song sparrow species and observed that the darker pigmented feathers were more resistant and they cited other research also published in 2004 that stated increased melanin proviided greater resistance They observed that the greater resistance of the darker birds confirmed Gloger s rule The evolution of coloration is based on sexual selection and it has been suggested that carotenoid based pigments may have evolved since they are likely to be more honest signals of fitness because they are derived from special diets or because carotenoids are also required for immune function Parasites The feather surface is the home for some ectoparasites notably feather lice Phthiraptera and feather mites Feather lice typically live on a single host and can move only from parents to chicks or mating birds and occasionally by phoresy This life history has resulted in most of the species being specific to the host and coevolving with the host making them of interest in phylogenetic studies Feather holes are chewing traces of lice most probably Brueelia spp lice on the wing and tail feathers They were described on barn swallows and because of easy countability many evolutionary ecological and behavioral publications use them to quantify the intensity of infestation Interestingly parasitic cuckoos which grow up in the nests of other species also have host specific feather lice and these seem to be transmitted only after they leave the host nest Birds maintain their feather condition by bathing in water dust bathing and preening A peculiar behavior of birds anting where ants are introduced into the plumage was suggested to help in reducing parasites but no supporting evidence has been found Human usage Shaft of Indian Peacock tail feather Feathers have a number of utilitarian cultural and religious uses Utilitarian functions Feathers are both soft and excellent at trapping heat thus they are sometimes used in high class bedding especially pillows blankets and mattresses They are also used as filling for winter clothing such as quilted coats and sleeping bags goose and eider down have great loft the ability to expand from a compressed stored state to trap large amounts of compartmentalized insulating air Bird feathers have long been used for fletching arrows Colorful feathers such as those belonging to pheasants have been used to decorate fishing lures Feathers of large birds most often geese have been and are used to make quill pens The word pen itself is derived from the Latin penna for feather The French nom de plume for pen name has a similar origin Feathers are also valuable in aiding the identification of species in forensic studies particularly in bird strikes to aircraft The ratios of hydrogen isotopes in feathers help in determining the geographic origins of birds Feathers may also be useful in the non destructive sampling of pollutants The poultry industry produces a large amount of feathers as waste and like other forms of keratin these are slow in their decomposition Feather waste has been used in a number of industrial applications as a medium for culturing microbes biodegradeable polymers and production of enzymes Feather proteins have been tried as an adhesive for wood board In religion and culture Eagle feathers have great cultural and spiritual value to American Indians in the USA and First Nations peoples in Canada as religious objects In the United States the religious use of eagle and hawk feathers are governed by the eagle feather law a federal law limiting the possession of eagle feathers to certified and enrolled members of federally recognized Native American tribes Various birds and their plumages serve as cultural icons throughout the world from the hawk in ancient Egypt to the bald eagle and the turkey bird in the United States In Greek mythology Daedelus the inventor and Icarus tried to escape his prison by attaching feathered wings to his shoulders with wax which was melted by the Sun In South America brews made from the feathers of Condors are used in traditional medications In India feathers of the Indian Peacock have been used in traditional medicine for snakebite infertility and coughs During the 18th 19th and even 20th Centuries a booming international trade in plumes to satisfy market demand in North America and Europe for extravagant head dresses as adornment for fashionable women caused so much destruction for example to egret breeding colonies that a major campaign against it by conservationists led to the Lacey Act and caused the fashion to change and the market to finally collapse Frank Chapman noted in 1886 that as many as 40 species of birds were used in about three fourths of the 700 ladies hats that he observed in New York City Evolution Main article Origin of avian flight Fossil feather of Archaeopteryx The functional view on the evolution of feathers has traditionally focused on insulation flight and display Discoveries of non flying Late Cretaceous feathered dinosaurs in China however suggest that flight could not have been the original primary function While feathers have been suggested as having evolved from reptilian scales there are numerous objections and more recent explanations have arisen from the paradigm of evolutionary developmental biology Theories of the scale based origins of feathers suggest that the planar scale structure was modified for their development into feathers by splitting to form the webbing however the developmental process involves a tubular structure arising from a follicle and the tube splitting longitudinally to form the webbing The number of feathers per unit area of skin is hig

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I am an expert from China Crafts Suppliers, usually analyzes all kind of industries situation, such as cane rattan furniture , rattan dining chair.
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