Anatomy and Physiology of Hair The study of Hair Trichology is the study of hair and its diseases. Hair growth is affected by: Genetics Age Hormones Appendage of the skin – threadlike outgrowth of the skin and scalp Due to the absence of nerves, there is no sense of feeling in the hair. Much of the hair on the body is invisible to naked eye Hormonal influence on male/female hair growth patterns Characteristics Genetics influences – hair color, thickness, quality, of Hair growth rate Hair contains melanin, which determines hair color Hair on scalp grows an average of 0.35 mm. per day Hair provides the body protection from environmental factors and UV radiation. Types of Hair Lanugo hair: Soft hair covers the fetus in the womb Lanugo hair usually sheds a few weeks after birth and is replaced with vellus or terminal hairs. Vellus hair: Very soft, fine, non-pigmented hair found in areas such as women’s cheeks or forehead. (also known as peach fuzz) Removing vellus hair can result in the production of stronger pigmented terminal hair. It is not recommended to shave, wax, or tweeze vellus hair. Terminal hair: Long, thick, pigmented hair found on arms, legs, head, brows, lashes, scalp and genitals. Vellus hair turns into terminal hair during puberty. Vellus and Terminal Hair Both males and females have the same number of hair follicles. Males have more terminal hair Females have more vellus hair Over time, vellus hair can become terminal Laser hair removal works best on terminal hair Hair Shaft Components of Hair Root • Located below the surface of the skin. Shaft • Located above the surface of the skin. Hair Root The hair shaft is made up of a protein called Keratin, which is produced in the lower part of the hair follicle, known as the bulb. The hair follicle is made up of epidermal cells in the shape of a tube or canal which Structure of extends deep into the dermis. Hair The areas below the skin’s surface consist of: Arrector pili Sebaceous Follicle Hair Root Hair Bulb Hair Papilla muscle glands Hair bulb – thick, structure that surrounds the papilla in the Terminology lower part of the hair root. This is where the hair growth of Hair production occurs. Hair Papilla – cone shaped elevation at the base of the follicle. Fits into the bulb. Provides hair growth and nourishment to the follicle. Nutrients are carried by blood vessels to the base of the bulb, creating new hair growth. Arrector pili muscle – attached to the base of the hair follicle. This muscle is responsible for causing goosebumps when we feel cold or scared. The muscle contracts and pulls the follicle forcing the hair to stand. Sebaceous glands – attached to the follicle and responsible for lubricating the skin and hair. When the arrector pili muscle contracts, protective lipids from the sebaceous glands disperse onto the skin and hair. Moderate amounts of sebaceous oils are necessary for healthy skin and hair. This Photo by Unknown Author is licensed under CC BY Hair color is determined by the amount of pigment called melanin found in hair, eyes, and skin. There are two forms of melanin: Eumelanin and Pheomelanin. Eumelanin – provides individuals black and brown pigment to the hair. What Primarily found in individuals Individuals with blonde hair Determines with darker skin types have very little eumelanin Hair Color? Pheomelanin – provides individuals red pigment to the hair. Primarily found in individuals with lighter skin type. How Melanin is Produced in Hair Melanin is a pigment produced by melanocytes found in the hair papilla. Each hair grows from a single follicle. As the hair is being formed, the melanocytes inject melanin into cells containing keratin. Keratin is the protein that is responsible for making our hair, skin, and nails. Differences in the types of melanin produce different hair colors. With age, the production of melanin reduces, and hair loses its color. Eventually the hair turns gray or white. Hair Growth Cycle Hair growth occurs in three stages: Anagen Phase: Growth stage in which new hair is produced This is the only phase in which laser hair removal is effective. Catagen Phase: Transitioning stage of hair growth. Hair grows upward and detaches itself. Telogen Phase: Resting stage in which hair moves up the follicle and appears above the skin’s surface. The hair may sit in the follicle or fall out. Once the hair sheds, the cycle repeats itself and goes back to the anagen phase. Every part of the body goes through the same three phases of the hair growth cycle. All three phases take place simultaneously since each hair follicle is independent and goes through a different phase at different times. Typically 80-90% the hair is in the Anagen phase, 1-2% is in the Catagen phase, and 10-14% is in the Telogen phase. Understanding Hair Growth Usually hair can grow from the papilla to the surface of the Cycle skin in about 6 to 12 weeks depending on its location. The longer the hair stays in the Anagen phase, the longer it will grow. Hair on the scalp can last for 3-7 years. The hair on legs, arms, and eyebrows can last 30-45 days. The Anagen is the only phase where laser hair removal is effective. It works best on coarse, dark black hair on a lighter skin type. Clients being treated should be informed that between 6-8 treatments may be required since not How Hair all hair will be in the anagen phase at the same time. Growth Treatments should be spaced out depending on the body area being treated. This is usually Relates to estimated at an interval equal to half the Telogen Lasers Phase. For areas on the face, treatments sessions should be 4-6 weeks apart. For underarms and bikini, treatment sessions should be 6-8 weeks apart. For areas on the legs and backs treatment sessions should be 8-10 weeks apart. Frequently Treated Areas of the Body Body area % Anagen % Telogen Duration of Follicle Density Follicle Depth Telogen Scalp 85% 15% 3 months 350/sq.cm 5-7mm Beard 70% 30% 3 months 500/sq.cm 2-4mm Upper Lip 65% 35% 6 weeks 500/sq.cm 1-2.5mm Axilla 30% 70% 3 months 65/sq.cm 4-5mm Chest/Back 30% 70% 9 months 70/sq.cm 2-5mm Breast 30% 70% 4 months 70/sq.cm 2-4mm Arms 20% 80% 6 months 80/sq.cm 2-4mm Legs 20% 80% 6 months 60/sq.cm 1-2.5mm Bikini 30% 70% 3 months 70/sq.cm 4-5mm Excessive Hair Growth Imbalance of hormones can lead to an excessive abnormal hair growth such as: Hirsutism and Hypertrichosis. Hirsutism Excessive hair growth of the hair, arms, and legs specially in women Hypertrichosis Excessive hair growth characterized by terminal or coarse hair in areas of the body where vellus hair is normally present. Polycystic Ovary Syndrome (PCOS) A condition in which women experience a hormonal imbalance causing them to produce higher levels of androgen, male hormones. Causes excessive hair growth in the following areas: Face Neck Chest Thighs Causes the following symptoms: Cysts on Lack of Depression Loss of hair Small breasts ovaries menstruation Permanent Hair Electrolysis Removal Methods of Hair Removal Permanent Hair Lasers Reduction Intense Pulse Light (IPL) The process of hair removal via electrical methods. Works by inserting small needles into hair follicles Electrolysis The only true method of permanently removing hair There are three Galvanic methods of Thermolysis Electrolysis: Blend Lasers and Intense Pulse Light (IPL) use concentrated rays of light to destroy growth cells of the hair bulb. A laser beam is emitted on the skin to damage hair follicles Lasers and It is most effective in the Anagen phase IPL Devices Lasers and IPL for hair removal are considered semi- permanent because the hair bulb is not always destroyed, causing regrowth in certain areas. Approximately 50-60% hair reduction can be seen after 12 weeks. The End.