CHAPTER 11 PROPERTIES OF THE HAIR AND SCALP

androgenic alopecia

AKA (androgenetic alopecia) hair loss characterized by miniaturization of terminal hair that is converted to vellus hair; in men, it is known as male pattern baldness

peptide bond

AKA (end bond) chemical bond that joins amino acids to each other, end to end, to form a polypeptide chain.

anagen phase

AKA (growth phase) phase during which new hair is produced.

hypertrichosis

AKA (hirsuties) condition of abnormal growth of hair, characterized by the growth of terminal hair in areas of the body that normally grow only vellus hair.

vellus hair

AKA (lanugo hair) short, fine, unpigmented downy hair that appears on the body, with the exception of the palms of the hands and the soles of the feet.

telogen phase

AKA (resting phase) the final phase in the hair cycle that lasts until the fully grown hair is shed.

tinea favosa

AKA (tinea favus) fungal infection characterized by dry, sulfur-yellow, cup-like crusts on the scalp called scutula.

polypeptide chain

a long chain of amino acids liked by peptide bonds.

salt bond

a weak, physical, cross-link side bond between adjacent polypeptide chains.

hydrogen bond

a weak, physical, cross-link side bond that is easily broken by water or heat.

hair porosity

ability of the hair to absorb moisture.

hair elasticity

ability of the hair to stretch and return to its original length without breaking.

alopecia

abnormal hair loss.

cysteine

an amino acid joined with another cysteine amino acid to create cystine amino acid.

cystine

an amino acid that joins together two peptide strands.

alopecia areata

autoimmune disorder that causes the affected hair follicles to be mistakenly attacked by a person's own immune system; usually begins with one or more small, round, smoothe bald patches on the scalp.

furuncle

boil; acute, localized bacterial infection of the hair follicle that produces constant pain.

side bonds

bonds that cross-link the polypeptide chains together and are responsible for the extreme strength and elasticity of human hair.

alopecia universalis

complete loss of body hair.

scatula

dry, sulfur-yellow, cup-like crusts on the scalp in tinea favosa or tinea favus.

hydrophilic

easily absorbs moisture; in chemistry terms, capable of combining with or attracting water (water-loving).

hair stream

hair flowing in the same direction, resulting from follicles sloping in the same direction.

whorl

hair that forms in a circular pattern on the crown of the head.

pediculosis capitis

infestation of the hair and scalp with head lice.

carbuncle

inflammation of the subcutaneous tissue caused by staphylococci; similar to a furuncle but larger.

medulla

innermost layer of the hair that is composed of round cells; often absent in fine and naturally blond hair.

proteins

long, coiled complex polypeptides made of amino acids.

terminal hair

long,coarse, pigmented hair found on the scalp, legs, arms, and bodies of males and females.

hair bulb

lowest part of a hair strand; the thickened, club-shaped structure that forms the lower part of the hair root.

cortex

middle layer of the hair; a fibrous protein core formed by elongated cells containing melanin pigment.

malassezia

naturally occurring fungus that is present on all human skin, but is responsible for dandruff when it grows out of control.

hydrophobic

naturally resistant to being penetrated by moisture.

hair cuticle

outermost layer of hair; consisting of a single, overlapping layer of transparent, scale-like cells that look like shingles on a roof.

keratinization

process by which newly formed cells in the hair bulb mature, fill with keratin, move upward, lose their nucleus, and die.

trichology

scientific study of hair and its diseases and care.

pityriasis steatoides

severe case of dandruff characterized by an accumulation of greasy or waxy scales mixed wth sebum, that stick to the scalp in crusts.

helix

spiral shape of a coiled protein created by polypeptide chains that intertwine with each other.

disulfide bond

strong chemical side bond that joins the sulfur atoms of two neighboring cysteine amino acids to create one cystine, which joins together two polypeptide strands like rungs on a ladder.

monilethrix

technical term for beaded hair.

fragilitas crinium

technical term for brittle hair.

pityriasis capitis simplex

technical term for classic dandruff; characterized by excessive production and accumulation of skin cells.

pityriasis

technical term for dandruff; characterized by excessive production and accumulation of skin cells.

canities

technical term for gray hair; results from the loss of the hair's natural melanin pigment.

trichorrhexis nodosa

technical term for knotted hair; it is characterized by brittleness and the formation of nodular swellings along the hair shaft.

tinea

technical term for ringworm, a contagious condition caused by fungal infection and not a parasite; characterized by itiching, scales, and sometimes, painful lesions.

trichoptilosis

technical term for split ends

postpartum alopecia

temporary hair loss experienced at the conclusion of a pregnancy.

lanthionine bonds

the bonds created when disulfide bonds are broken by hydroxide chemical hair relaxers after the relaxer is rinsed from the hair.

catagen phase

the brief transition period between the growth and resting phases of a hair follicle. It signals the end of the growth phase.

COHNS elements

the five elements- carbon, oxygen, hydrogen, nitrogen and sulfur- that make up human hair, skin, tissue, and nails.

hair density

the number of individual hair strands on 1 square inch (2.5 square centimeters) of scalp

hair root

the part of the hair located below the surface of the epidermis.

hair shaft

the portion of hair that projects above the epidermis.

wave pattern

the shape of the hair strands; described as straight, wavy, curly, and extremely curly.

hair follicle

the tube-like depression or pocket in the skin or scalp that contains the hair root.

hair texture

thickness or diameter of the individual hair strand.

alopecia totalis

total loss of scalp hair.

cowlick

tuff of hair that stands straight up.

amino acids

units that are joined together end to end like pop beads by strong, chemical peptide bonds( end bonds) to form the polypeptide chains that comprise proteins.

ringed hair

variety of canities characterized by alternating bands of gray and pigmented hair throughout the length of the hair strand.