Glossary Terms
Below we have compiled a list of terms that are used when referencing anything to do with hair loss/hair transplant from A to Z (V in this case). Feel free to use them as reference. (If you have a suggestion that you think would be useful, please contact us so we can review and include it.)
A
Alopecia: [Gk, alopex, fox (mange)], partial or complete lack of hair resulting from various disorders or conditions.
Alopecia Androgenetica: [Gk, alopex, fox (mange) + Gk, andros + genein, to produce], the medical name for male or female pattern baldness.
Alopecia Areata: [Gk, alopex, fox (mange) + L, area, open space], hair loss in sharply defined patches.
5 alpha-reductase: the enzyme necessary to convert testosterone to dihydrotestosterone (DHT). Type 1 5-alpha reductase is found primarily in the skin and type 2 5-alpha reductase is found primarily in the prostate.
Anagen: [Gk, ana, up, again + genein, to produce], the growing phase of hair, which shows great variation, ranging from two to six or more years.
Androgen: [Gk, andros + genein, to produce], any steroid hormone that increases male characteristics.
Apoptosis: [Gk, apo, separation + ptosis, falling], programmed cell death.
Azelaic Acid: a naturally occurring saturated dicarboxylic acid with the chemical name of 1,7-heptanedicarboxylic acid and a molecular weight of 188.22. Azelaic acid is a dietary component of whole grain cereals and animal products. Azelaic acid (0.1 to 3.0 mmol/l) has been shown to produce a competitive concentration dependent inhibition of 5-alpha reductase activity in human skin and is used topically to inhibit the synthesis of DHT in the scalp.
B
Biopsy: [Gk, bios, life + opsis, view], the removal of a small piece of living tissue from an organ or other part of the body for microscopic examination.
C
Catagen: [Gk, kata, down, under + genein, to produce], the short transition phase of the hair growth cycle, lasting two to three weeks.
Clone: [Gk, klon, a plant cutting], a group of genetically identical cells or organisms derived from a single common cell.
Crown: [L, corona, an encircling structure], the upper part of an organ or structure, such as the top of the head.
Cuticle: The outer surface of hair, composed of overlapping scales made of colorless keratin protein. It gives hair luster and shine and also provides some of its strength.
D
Dermal Papilla: The dermal papilla is situated at the base of the hair follicle. The dermal papilla contains nerves and blood vessels, which supply glucose for energy and amino acids to make keratin. This structure is extremely important in the regulation of hair growth since it has receptors for both androgens and hair-promoting agents.
Dermatology: [Gk, derma, skin + logos, science], the study of the skin, including the anatomy, physiology, and pathology of the skin and the diagnosis and treatment of skin disorders.
Dermis: [Gk, derma, skin], the layer of the skin, just below the epidermis, consisting of papillary and reticular layers and containing blood and lymphatic vessels, nerves and nerve endings, glands and hair follicles.
DHT: acronym for dihydrotestosterone. Classified as a ‘sex hormone’, there is no well delineated relationship to the levels of DHT and libido or sexual activity. Other than promoting hair growth on the face and upper pubis (but having just the opposite effect on the scalp), the role of DHT in the adult human male is a mystery.
Donor Area: Area of the scalp (usually along the sides) where hair is extracted from to be transplanted to the bald area.
Dutasteride: a medication currently under development by GlaxoSmithKline, which is a dual inhibitor of the 5-alpha reductase enzymes responsible for converting testosterone to DHT.
E
Effluvium: [L, effluvium, a flowing out], an outflow, which may pertain to sudden, severe hair shedding.
Epidermis: [Gk, epi, on or upon + derma, skin], the superficial, avascular, layers of the skin, made up of an outer, dead cornified portion and a deeper, living, cellular portion. Altogether, these layers are between 0.5 to 1.1 mm.
Etiology: [Gk, aitia, cause + logos, science], the cause of a disease.
F
Finasteride: the generic name for Propecia and Proscar, which are drugs that bind with the type 2 5-alpha reductase enzyme and reduce the amount of DHT in the prostate and serum.
Follicle: [L, folliculus, small bag], a pouch like depression, such as the hair follicles within the dermis that enclose the hair roots.
Frontal Hairline: [L, frons, forehead], the demarcation of vellus to terminal or intermediate hair in and adjacent to the midline of the anterior part of the head.
G
Generic: [L, genus, kind], of or pertaining to a substance, product, or drug that is not protected by trademark; identical in chemical composition but not necessarily equivalent in therapeutic effect.
Glycerin or Glycerine: [Gk, glykeros, sweet], a sweet, colorless, oily fluid that is a pharmacologic grade of glycerol. Glycerin is used as a moistening agent for chapped skin, as an ingredient of suppositories for constipation and as a sweetening agent and vehicle for drug preparations.
H
Hamilton-Norwood: a graphic scale representing the extent of hair loss / recession of alopecia androgenetica in males.
Hirsutism: [L, hirsutus, hairy], excessive body or facial hair as a result of heredity, hormonal dysfunction, porphyria or medication. Also called hypertrichosis.
Hormone: [Gk, hormaein, to set in motion], a complex chemical substance produced in one part or organ of the body that initiates or regulates the activity of an organ or a group of cells in another part of the body.
Hypertrichosis: excessive hair growth over and above the normal for the age, sex and race of an individual, in contrast to hirsutism, which is excess hair growth in women following a male distribution pattern. Hypertrichosis can develop all over the body or can be isolated to small patches.
Hypothyroidism: (underactive thyroid gland) is the term used to describe a condition in which there is a reduced level of thyroid hormone (thyroxine) in the body. This can cause various symptoms, including: tiredness, weight gain, constipation, aches, dry skin, lifeless hair/hair loss and feeling cold.
I
Idiopathic: [Gk, idios, private, distinctive, peculiar + pathos, disease], without a known cause.
Infundibulum: is the cup or funnel in which a hair follicle grows, also The superior, or highest portion, of the hair follicle.
Intermediate Hair: intermediate scalp hairs are approximately 1 cm in length. They lack the texture of terminal hair, but have much more thickness and body than vellus hair.
In Vitro: [L, in, within + vitreous, glassware], of a biologic reaction occurring in laboratory apparatus.
In Vivo: [L, in, within + vivo, alive], of a biologic reaction occurring in a living organism.
Isthmus: is the shortened segment of the hair follicle, extending from the attachment of the erector pili muscle (bulge region) into the entrance of the sebaceous gland duct.
K
Keratin: [Gk, keras, horn], a fibrous, sulfur-containing protein that is the primary component of the epidermis, hair, nails and enamel of the teeth.
Ketoconazole: an antifungal medication that inhibits biosynthesis of ergosterols or other sterols.
L
Ludwig Staging: a graphic representation of the severity of alopecia androgenetica in women, originally published in 1977 in the British Journal of Dermatology.
Lunago: [L, down], the soft, fine hair that covers much of the foetus beginning in the fifth month and is usually shed before birth.
M
Micrograft: [Gk, micros, small] means grafts with 1 or 2 hairs, minigrafts are those with 3 or 4 hairs, and a megasession is a procedure in which more than 1000 micrografts and minigrafts are inserted in a single session.
Midline: Region towards the middle of the scalp.
Miniaturisation: The destructive process by which dihydrotestosterone (DHT) shrinks hair follicles; a key marker of androgenetic alopecia.
Minoxidil: a piperidinopyrimidine derivative vasodilator that possesses hair growth stimulant properties, possibly involving direct stimulation of hair follicle epithelial growth. The first FDA drug approved for the treatment of MPB.
O
Occiput: [L, occiput, atlas], the back part of the head.
Oestrogen: [Gk, oistros, gadfly + genein, to produce], one of a group of hormonal steroid compounds that promote the development of female secondary sex characteristics.
P
Papilla: The small root area at the base of hair, which receives the nutrients needed for hair growth.
Pharmacodynamics: [Gk, pharmakon, drug + dynamis, power], the study of how a drug acts on a living organism.
Posterior Scalp: The area at the back of the head.
Pilosebaceous Unit: [L, pilus, hair + sebum, fat], of or pertaining to a hair follicle and its oil gland.
Proprietary: [L, proprietas, a property], of or pertaining to a product, such as a drug or device, that is made for profit.
Propylene Glycol: a colourless viscous liquid used as a solvent in the preparation of certain medications. It also inhibits the growth of fungi and microorganisms.
R
Receptor Site: [L, recipere, to receive +situs, location], a location on a cell surface where certain molecules, such as enzymes, neurotransmitters, or viruses, attach to interact with cellular components.
Recession: [L, recedere, to retreat], a regression.
Recipient Site: The bald area where the extracted hairs (usually from the donor area) are transplanted to.
Retin-A: the proprietary name for a preparation of retinoic acid, used in the treatment of acne and sun damage to the skin
Retinoic Acid (also tretinoin, isotretinoin or all-trans-retinoic acid): the cis-trans form of vitamin A. Retinoids act as a mild chemical peel on the skin and are very important to all epithelial structures.
S
Scleroderma: [Gk, skliro, hard, derma, skin], a chronic hardening and contraction of the skin and connective tissue, either locally or throughout the body. It can cause hair loss over the affected areas.
Sebaceous: [L, sebum, sweat], fatty, oily or greasy, usually referring to the oil-secreting glands of the skin or to their secretions.
Sebum: [L, grease], the oily secretion of the sebaceous glands of the skin, composed of keratin, fat and cellular debris.
Steroid: [Gk, stereos,solid + eidos, form], any of a large number of hormonal substances with a similar basic chemical structure, produced mainly in the adrenal cortex and gonads.
Superoxide Dismutase (SOD): chemicals that catalyses the destruction of oxygen free radicals. It protects oxygen metabolising cells against the harmful effects of superoxide free radicals.
Suture: Stich.
T
Telogen: [Gk, telos, end + genein, to produce], the resting phase of the hair growth cycle lasting approximately 100 days.
Temples or Temporal Areas: [L, tempus, temple], the lateral-frontal regions of the head.
Terminal Hair: [L, terminus, boundary] of or pertaining to the thicker hair on the scalp that are medullated and have a growth phase of many years.
Testosterone: a naturally occurring androgenic hormone.
Theory of Donor Dominance: Scientific basis for hair transplantation stating that hair’s genetic code resides within the hair follicle and not in the recipient site into which it is transplanted.
Trichotillomania: [Gk, trikhos, hair, tillein, pull out (hair)] a compulsive desire to pull out one’s hair.
V
Vellus: the soft, fine hair covering all parts of the body except palms, soles and areas where other types of hair are normally found. True vellus hairs have no erector pili muscle, but have large sebaceous glands. Vellus scalp hairs achieve lengths less than 1 cm.
Vertex: [L, vertex, summit], the top of the head towards the posterior portion, including the area or areas at which the hair grows in a spiral pattern.