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1. any thin, threadlike structure.
2. especially, the specialized epidermal structure produced only by mammals, developing from a papilla sunk in the corium. The life cycle of a hair (hair cycle) consists of three phases, called anagen, catagen, and telogen. Called also pilus.
3. the aggregate of such structures.
bamboo hair trichorrhexis nodosa.
beaded hair hair marked with alternate swellings and constrictions; seen in monilethrix.
burrowing hair one that grows horizontally in the skin, causing a papule that may become infected; see also pili cuniculati, under pilus.
club hair a hair whose root is surrounded by a bulbous enlargement composed of keratinized cells, preliminary to normal loss of the hair from the follicle.
Frey's h's stiff hairs mounted in a handle; used for testing the sensitiveness of pressure points of the skin.
ingrown hair one that has curved and reentered the skin, causing a papule that may become infected. See also pili incarnati, under pilus.
lanugo hair the fine hair on the body of the fetus.
moniliform hair beaded hair.
pubic hair the hair on the external genitalia; called also pubes.
sensory h's hairlike projections on the surface of sensory epithelial cells.
tactile h's hairs sensitive to touch.
taste h's short hairlike processes projecting freely into the lumen of the pit of a taste bud from the peripheral ends of the taste cells.
terminal hair the coarse hair on various areas of the body during adult years.
twisted hair a hair that is twisted through an axis of 180 degrees at spaced intervals, being abnormally flattened at the site of twisting. See also pili torti, under pilus.
Etymology: L, in, within; AS, growen, to grow, haer
a hair that fails to follow the normal follicle channel to the surface, with the free end becoming embedded in the skin. The hair then acts like a foreign body, and inflammation and suppuration follow.
in·grown hair(in'grōn hār)
Hair that grows at more acute angles than is normal, and in all directions; it incompletely clears the follicle, turns back in, and causes pseudofolliculitis.
1. a threadlike keratinized epidermal structure developing from a follicle sunk in the dermis, produced only by mammals and characteristic of that group of animals. Also, the aggregate of such hairs.
2. various other threadlike structures.
hairlike attachments of the epithelial cells of the inner ear.
in cats, a short thick, bristly hair underneath the top coat.
coat hairs occur in groups of about three primary follicles and a variable number of secondary follicles.
one that grows horizontally in the skin.
sensory neuroepithelial cells which have hair-like processes; found in organ of Corti, ampullary crests and utricle and saccule of the inner ear.
a hair whose root is surrounded by a bulbous enlargement composed of keratinized cells, preliminary to normal loss of the hair from the follicle.
see coat (1).
see guard hair (below).
one of the tubular invaginations of the epidermis enclosing the hair roots and from which the hairs grow.
hair follicle unit
granuloma in the esophageal wall caused by swallowed hairs acting as foreign bodies.
hair growth cycle
a period of growth, called anagen, is followed by a transitional stage, called catagen, and then a period of inactivity in the hair follicle, called telogen, lasting until the cycle starts again. The duration of each stage varies with the species, anatomical location, genetic influence, and a variety of environmental and physiological factors.
the coarse, stiff and often longer and more prominent hairs in a haircoat with an undercoat. For example, the darkly colored, outer hairs of a German shepherd dog. Called also primary hair, master hair, cover hair.
one that has curved and re-entered the skin.
the fine hair on the body of the fetus.
see guard hair (above).
see guard hair (above).
see thrix annulata.
finer and growing from a more superficial follicle than a guard hair; forms the undercoat.
hairlike projections on the surface of sensory epithelial cells.
the vibrissae or whiskers located on the muzzle and face of many species has an endothelium-lined blood sinus between the inner and outer layers of the dermal portion of the follicle with a rich nerve supply. This structure serves to increase sensory perception.
includes auditory, guard, sensory, tactile, taste, tylotrich hairs (see this list).
the hairs in the coat of animals are inclined in one or other direction so that collectively they create streams that meet at vortices or cowlicks.
hairs particularly sensitive to touch.
short hairlike processes projecting freely into the lumen of the pit of a taste bud from the peripheral ends of the taste cells.
one with a different, usually darker, color at the tip; seen in Chinchilla cats.
special hairs that act as rapid-adapting mechanoreceptors; large, primary follicles with a ring of neurovascular tissue around them. Always associated with a tylotrich pad, a local area of epidermal thickening with a layer of highly vascular and well-innervated connective tissue below.