hair

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hair

 [hār]
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.
Structure of hair and hair follicles. From Applegate, 2000.
3. the aggregate of such structures.
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.

hair

(hār), [TA]
1. One of the fine, keratinized filamentous epidermal growths arising from the skin of the body of mammals except the palms, soles, and flexor surfaces of the joints; the full length and texture of hair varies markedly in different body sites. Synonym(s): pilus (1) [TA]
2. One of the fine, hairlike processes of the auditory cells of the labyrinth, and of other sensory cells, called auditory hair, sensory hair, etc.
Synonym(s): thrix [TA]
[A.S. haer]

hair

trichophobia, trichopathophobia.

hair

(hār) pilus; a threadlike structure, especially the specialized epidermal structure composed of keratin and developing from a papilla sunk in the dermis, produced only by mammals and characteristic of that group of animals. Also, the aggregate of such hairs.hair´y
Enlarge picture
Hair in longitudinal section (A), and in cross section (B), showing the surrounding root and dermal sheaths.

bamboo hair  trichorrhexis nodosa.
beaded hair  hair marked with alternate swellings and constrictions, as in monilethrix.
burrowing hair  one that grows horizontally beneath the surface of the skin.
club hair  one whose root is surrounded by a bulbous enlargement composed of keratinized cells, preliminary to normal loss of the hair from the follicle.
ingrown hair  one that emerges from the skin but curves and reenters it.
lanugo hair  lanugo.
resting hair  see telogen.
sensory hairs  hairlike projections on the cells of sensory epithelium.
taste hairs  clumps of microvilli that form short hairlike processes projecting into the lumen of a taste pore from the peripheral ends of the taste cells.
Enlarge picture
Taste hairs protruding from the pore of a taste bud.
terminal hair  the coarse hair on various areas of the body during adult years.
twisted hair  one which at spaced intervals is twisted through an axis of 180 degrees, being abnormally flattened at the site of twisting.
vellus hair  vellus (1).

hair

(hâr)
n.
1.
a. Any of the cylindrical, keratinized, often pigmented filaments characteristically growing from the epidermis of a mammal.
b. A growth of such filaments, as that forming the coat of an animal or covering the scalp of a human.
2. A filamentous projection or bristle similar to a hair, such as a seta of an arthropod or an epidermal process of a plant.

hair

Etymology: AS, haer
a filament of keratin consisting of a root and a shaft formed in a specialized follicle in the epidermis. There are three stages of hair development: anagen, the active growing stage; catagen, a short interlude between the growth and resting phases; and telogen, the resting (club) stage before shedding. Scalp hair grows at an average rate of 1 mm every 3 days, body and eyebrow hair at a much slower rate. Hair plucking does not stop hair growth. See also hirsutism, lanugo.
A threadlike epidermal appendage consisting of keratinized dead cells that extrudes from a dividing basal layer

hair

Dermatology A threadlike epidermal appendage consisting of keratinized dead cells that extrudes from a dividing basal layer. Related terms are Anagen hair, Bamboo hair, Bayonet hair, Bundled hair, Catagen hair, Corkscrew hair, Green hair, Paintbrush hair, Pubic hair, Ringed hair, See-through hair, Telogen hair, Terminal hair, Vellus hair, Whisker hair.

hair

(hār) [TA]
1. One of the fine, keratinized filamentous epidermal growths arising from the skin of the body of mammals except the palms, soles, and flexor surfaces of the joints; the full length and texture of hair varies markedly in different body sites.
2. One of the fine, hairlike processes of the auditory cells of the labyrinth, and of other sensory cells, called auditory hair, sensory hair, and other types.
Synonym(s): thrix.
[A.S. haer]

hair

(har)
1. A keratinized, threadlike outgrowth from the skin of mammals.
Enlarge picture
HAIR AND ADJACENT STRUCTURES OF CROSS-SECTION OF SKIN
2. Collectively, the threadlike outgrowths that form the fur of animals or that grow on the human body.

A hair is a thin, flexible shaft of cornified cells that develops from a cylindrical invagination of the epidermis, the hair follicle. Each consists of a free portion or shaft (scapus pili) and a root (radix pili) embedded within the follicle. The shaft consists of three layers of cells: the cuticle or outermost layer; the cortex, forming the main horny portion of the hair; and the medulla, the central axis. Hair color is due to pigment in the cortex. See: illustration

Hair in each part of the body has a definite period of growth, after which it is shed. In the adult human there is a constant gradual loss and replacement of hair. Hair of the eyebrows lasts only 3 to 5 months; that of the scalp 2 to 5 years. Baldness or alopecia results when replacement fails to keep up with hair loss. It may be hereditary or due to pathologic conditions such as infections or irradiation injury. Cytotoxic agents used in cancer chemotherapy may cause temporary loss of hair. See: alopecia

auditory hair

The stereocilia of a specialized epithelial cell. These are present in the ear in the spiral organ of Corti, concerned with hearing; and in the crista ampullaris, macula utriculi, and macula sacculi, concerned with equilibrium.

bamboo hair

Sparse, brittle hair with bamboo-like nodes. The nodes are partial fractures of the hair shaft, caused by atrophy of the hair.
Synonym: clastothrix; trichorrhexis nodosa

beaded hair

Swellings and constrictions in the hair shaft caused by monilethrix.

burrowing hair

A hair that grows horizontally under the skin, causing a foreign body reaction.

gustatory hair

Any of several fine hairlike processes extending from the ends of gustatory cells in a taste bud. They project through the inner pore of a taste bud. Synonym: taste hair

ingrown hair

A hair that reenters the skin, causing a foreign body reaction.

kinky hair

Short, sparse, tightly twisted hair that may be poorly pigmented.

lanugo hair

See: lanugo

moniliform hair

Monilethrix.

moth-eaten hair

Patchy areas of baldness, with poorly defined borders. This type of alopecia is one of the cutaneous hallmarks of syphilis.

pubic hair

Hair over the pubes, which appears at onset of sexual maturity. The distribution is somewhat different in men than in women.
See: mons veneris; mons pubis

sensory hair

Specialized epithelial cells with hairlike processes.

tactile hair

Hair that is receptive to touch or contact.

taste hair

Gustatory hair.

terminal hair

The long, coarse, pigmented hair of the adult.

twisted hair

Congenitally deformed hair that is short, brittle, and coiled.

hair

The filamentary keratin secretion of follicles in the skin. The outer layer, or cuticle, of each hair is made of overlapping flat cells arranged like roofing slates. Below this is the thick cortex of horny cells and the core of softer rectangular cells. The hair colour comes from pigment cells (melanocytes) of uniform colour present in differing concentration. Very curly hair comes from curved follicles.

hair

  1. (in plants) a filamentous outgrowth from an epidermal cell that may have a secretory function (in glands), an absorbing function (in root hairs), or a function in trapping and preventing air movement of the leaf surface, so lowering the rate of TRANSPIRATION.
  2. (in animals) a filamentous structure of mammalian skin formed of cornified epidermal cells that multiply in the hair follicle.

hair

(hār) [TA]
1. One of the fine, keratinized filamentous epidermal growths arising from the skin of the body of mammals except the palms, soles, and flexor surfaces of the joints.
2. One of the fine, hairlike processes of the auditory cells of the labyrinth, and of other sensory cells, called auditory or sensory hair.
[A.S. haer]

hair

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.

auditory h's
hairlike attachments of the epithelial cells of the inner ear.
awn hair
in cats, a short thick, bristly hair underneath the top coat.
hair beds
coat hairs occur in groups of about three primary follicles and a variable number of secondary follicles.
burrowing hair
one that grows horizontally in the skin.
hair cells
sensory neuroepithelial cells which have hair-like processes; found in organ of Corti, ampullary crests and utricle and saccule of the inner ear.
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.
hair coat
see coat (1).
cover hair
see guard hair (below).
hair follicle
one of the tubular invaginations of the epidermis enclosing the hair roots and from which the hairs grow.
Enlarge picture
Longitudinal section of hair follicle. By permission from Smith BP, Large Animal Internal Medicine, Mosby, 2001
hair follicle unit
hair granuloma
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.
guard hair
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.
ingrown hair
one that has curved and re-entered the skin.
lanugo hair
the fine hair on the body of the fetus.
master hair
see guard hair (above).
primary hair
see guard hair (above).
ringed hair
see thrix annulata.
secondary hair
finer and growing from a more superficial follicle than a guard hair; forms the undercoat.
sensory h's
hairlike projections on the surface of sensory epithelial cells.
sinus hair
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.
specialized hair
includes auditory, guard, sensory, tactile, taste, tylotrich hairs (see this list).
hair streams
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.
tactile h's
hairs particularly 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.
tipped hair
one with a different, usually darker, color at the tip; seen in Chinchilla cats.
tylotrich hair
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.

Patient discussion about hair

Q. i am 12 and my hair is falling out what do i do? there is like a hair ball in my tub

A. First of all you are going through puberty and the hormonal levels in your body are changing, this could cause accelerated hair loss that will go away. However, if you feel like you are having severe hair loss you should go and get blood tests for the evaluation of several vitamin defficiencies (B12, Folic acid and Iron), that can be the reason. Soemtimes a lack in our nutrition can be the reason for losing hair.

Q. What medications cause hair loss? I have RA, high blood pressure, high cholesterol, allergies and depression for which I take medication. Which of these cause hair loss?

A. any one of them can, you need to ask your pharmacist about it

Q. I went to a new hair dresser a to get my highlights done. and I think something is terribly wrong with my scalp. After washing the color away I already felt my scalp is tender, so he put some natural mask on my hair which he said will make it soft and nice, and calm the roots. A couple of days has past now and I still feel as though my scalp is a bit burning, and I think I am losing more hair than normally. So I am a “BIT” bit panicking here. Did he damage my scalp? How can I make the burning feeling go away? My friend said it is probably an allergic reaction to the active materials in the coloring or the natural mask, but I am usually not allergic to anything. Should I see a doctor?HELP!!!!

A. because of a very amusing story i'll tell someday - i know i'm allergic to P-Phenylenediamine or CPPD Black Rubber Mix that hair dyes sometime have. i also felt a burning sensation and lost some hair(that grew back ..) so i looked for alternative hair dyes and found some..just google hypoallergenic hair dyes. i recommend going to see a dermatologist just to be safe and get tested to see if you are really allergic.

More discussions about hair