H
Part of the hair shaft that projects above the epidermis
Hair Shaft
tube-like structure in the skin or scalp that surrounds the hair root and anchors the hair in the skin
Hair Follicle
form the building blocks of protein; link together end to end like pop beads by strong, chemical peptide bonds (end bonds) to form the polypeptide chains that comprise proteins
Amino Acids
scientific study of hair and its diseases and care
Trichology
found at base of the follicle; has a bulb shape and contains living cells that will form the hair strand
Hair Bulb
part of the hair located below the surface of the epidermis
Hair Root
also known as an end bond; chemical bond that joins amino acids to each other, end-to-end, to form a polypeptide chain
Peptide Bond
also known as the growth phase; hair phase during which new hair is produced
Anagen Phase
hair that grows straight up or at a different angle than the other hair; usually more noticeable at the crown
Cowlick
thickness or diameter of an individual hair strand
Hair Texture
small involuntary muscle in the dermis that attaches to the hair follicle; contraction of the muscle causes hair to stand, causing goose-bumps
Arrector Pili Muscle
also known as oil glands; glands connected to hair follicles; secrete sebum
Sebaceous Glands
fibrous protein layer of the hair; responsible for the strength, elasticity, and color of hair
Cortex
process by which newly formed cells in the hair bulb mature, fill with keratin, move upward, lose their nucleus, and die
Keratinization
measures the number of individual hair strands on 1 square inch (2.5 square centimeters) of scalp
Hair Density
fibrous protein of cells that is also the principal component of skin, hair, and nails
Keratin
innermost layer found in coarse hair and beard hair; known as hair’s pith or core; absent in fine hair
Medulla
long chain of amino acids linked by peptide bonds
Polypeptide Chain
five elements—carbon, oxygen, hydrogen, nitrogen, and sulfur—that make up human hair, skin, tissue, and nails
COHNS elements
amount of movement or shape of the hair strand; described as straight, wavy, curly, or coily
Wave Pattern
occurs when hair leaves the follicles at an angle; hair grows in a circular pattern on the crown of the head
Whorl
yellow to red pigment found in natural blonde to red shades of hair
Pheomelanin
brief transition period between the growth and resting phases of a hair follicle; signals the end of the growth phase
Catagen Phase
weak physical cross-link side bond between adjacent polypeptide chains that is broken by changes in pH
Salt Bond
bonds created when disulfide bonds are broken by hydroxide chemical hair relaxers
Lanthionine Bonds