Cats are known for their cleanliness, spending many hours licking their coats.[122] The cat's tongue has backwards-facing spines about 500 micrometers long, which are called papillae. These are quite rigid, as they contain keratin.[123] These spines allow cats to groom themselves by licking their fur, with the rows of papillae acting like a hairbrush. Some cats, particularly longhaired cats, occasionally regurgitate hairballs of fur that have collected in their stomachs from grooming. These clumps of fur are usually sausage-shaped and about two to three centimeters long. Hairballs can be prevented with remedies that ease elimination of the hair through the gut, as well as regular grooming of the coat with a comb or stiff brush.[122] Some cats can develop a compulsive behavior known as psychogenic alopecia, or excessive grooming. The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste (gustation), as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly supplied with nerves and blood vessels. In humans a secondary function of the tongue is phonetic articulation. The tongue also serves as a natural means of cleaning one's teeth.[2] The ability to perceive different tastes is not localised in different parts of the tongue, as is widely believed.[3] This error arose because of misinterpretation of some 19th-century research (see tongue map). Keratin (/?k?r?t?n/[1][2]) is a family of fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is also the key structural component of hair and nails. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and insoluble and form strong unmineralized tissues found

in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin. Psychogenic alopecia, also called over-grooming or psychological baldness,[1][2] is a compulsive behavior that affects domestic cats. Generally, psychogenic alopecia does not lead to serious health consequences or a decreased lifespan. Grooming is a natural behavior for cats. Cats spend 5%-25% of their waking hours grooming.[3] Grooming becomes excessive when it takes precedence over other activities or no longer seems functional.[2][3] Excessive grooming, which can lead to hair loss, skin wounds, and ulceration, can result from chronic stress or develop in cats who already exhibit nervous temperaments. Even when the source of stress is resolved or removed, excessive grooming may continue.[2] There may be some genetic basis for the behavior, and it predominantly affects purebred cats of oriental breeds, but can develop in any feline. Female cats appear more susceptible.[2] Environmental factors suspected of causing over grooming include flea allergy, boredom, food allergy, dust or pollen causing an allergic reaction, constipation and/or urinary tract infection caused by avoidance of a dirty litter tray, dermatitis, anxiety caused by inconsistent meal times. Deprivation of sunlight could be the part of the problem for indoors only cats. [edit]Symptoms Areas affected are those the cat can access most easily, including the abdomen, legs, flank, and chest.[2] Baldness, usually beginning with the abdomen[1] Obvious over-grooming (although some cats may only engage in the behavior in the absence of owners)[1] Redness, rashes, pus, scabs on the bald area or areas traumatized by over-grooming[1] A highly irritable cat may even cut its face with the claw of its hind foot if over-zealously scratching the back of its head.