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

Technical term for gray hair; results from the loss of the hair’s natural melanin pigment.

Complete loss of body hair.

Hair loss characterized by miniaturization of terminal

hair that is converted to vellus hair; in men, it is known as male pattern baldness.

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

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.

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

Tuft of hair that stands straight up.

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

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, smooth bald patches on the scalp.

Technical term for brittle hair.

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.

Also known as growth phase; phase during which new hair is produced.

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