trichology
the scientific study of hair and it's diseases
hair root
located below the surface of the epidermis
hair shaft
projects above the epidermis
five main structures of the hair root
hairroots air follicle, hair bulb, dermal papilla, arrector pili muscle, and sebaceous oil glands
hair follicle
tube like depression or pocket in the skin of scalp that contains the root. It extends downward from the epidermis into the dermis where it surrounds the dermal papilla.
hair bulb
lowest part of the hair strand- thickened club shaped structure that forms the lower part of the hair root-the lower part of the hair bulb fits over and covers the dermal papilla
dermal papilla
small, cone shaped elevation located at the base of the hair follicle that fits into the hair bulb- it provides the nutrients for hair growth-"mother of hair
arrector pili
small involuntary muscle in the base of the hair follicle
sebaceous glands
oil glands in the skin that are connected to the hair follicles. they secrete a fatty or an oily substance called sebum, which lubricates the skin- the elasticity of the hair and its natural color are the result of the unique protein structures located wi
sebum
substance secreted by the sebaceous glands/lubricates the skin
hair cuticle
outermost layer of the hair- consists of a single overlapping layer of transparent scale like cells that look like shingles on a roof
cortex
middle layer of the hair- it is a fibrous protein core formed by elongated cells containing melanin pigment
medulla
innermost layer of the hair- composed of round cells. generally only coarse hair contains a medulla
hair is what percent protein?
90%
amino acids
units that are joined together end to end like pop beads by strong, chemical peptide bonds to form the polypeptide chains that comprise protein
hydrogen bonds
weak, physical, cross-link side bond that is easily broken by water or heat. They account for about 1/3 of the hair's overall strength-they reform when the hair is dry
salt bond
weak, physical cross-link side bond between adjacent polypeptide chains. Easily broken by strong alkaline or acidic solutions-account for 1/3 of the hair's overall strength
disulfide bond
strong, chemical side bond- joins the sulfur of the atoms of two neighboring cysteine amierno acids to create one cystein-they are broken by permanent waves and chemical relaxers
wave pattern
refers to the shape of the hair strand
eumelanin
provides natural colors ranging from dark brown to black color to hair
pheomelanin
natural colors ranging from red and ginger to yellow and blond tones
pityriasis
technical term for dandruff
pityriasis steatoides
severe case of dandruff
Tinea
technical term for ringworm-caused by a fungal organism
canities
technical term for gray hair
fragilitis crinium
technical term for brittle hair
trichoptilosis
technical term for split ends
texture
thickness or diameter of the individual hair strand-coarse, medium, fine
porosity
ability of the hair to absorb moisture
elasticity
ability of the hair to stretch and return to it's normal length without breaking