Milady Chapter 11 - Properties of Hair and Scalp

Trichology and Hair Structure

• Trichology is the scientific study concerning hair, its diseases, and care.
• A mature human hair strand consists of two parts: the hair shaft and the hair root.
• Hair follicles are tube-like structures in the skin that house the hair root; absent on the soles of the feet and palms.
• The arrector pili is a small muscle at the base of each hair follicle, contributing to goosebumps.

Hair Composition and Growth

• Sebum, produced by sebaceous glands, is an oily substance that lubricates hair.
• Healthy hair cuticles allow chemical penetration when exposed to alkaline pH levels.
• The medulla, the innermost layer of hair, is made up of round cells.
• Keratinization is the process where living cells mature and ascend in the hair shaft.
• Human hair primarily consists of carbon, oxygen, hydrogen, nitrogen, and sulfur.

Hair Properties and Characteristics

• Peptide bonds link amino acids forming the proteins in hair.
• Pheomelanin is the type of melanin responsible for red, ginger, yellow, and blond hair tones.
• Asian hair tends to be extremely straight, influencing styling approaches.
• Hair texture is classified into coarse, medium, or fine categories.

Density, Porosity, and Elasticity

• Hair density measures the number of hair strands in one square inch of the scalp.
• Chemically treated hair with low porosity requires stronger alkaline solutions compared to high porosity hair.
• Wet hair with normal elasticity can stretch up to 50% of its original length.

Hair Care and Scalp Conditions

• An oily scalp is best treated with normalizing shampoo.
• Vellus hair is a type that almost never contains medulla.
• The anagen phase is when new hair growth occurs, lasting typically three to five years.
• The average rate of healthy scalp hair growth is approximately 1/2 inch (1.25 cm) per month.

Hair Loss and Conditions

• "Canities" refers to graying hair, while "Hypertrichosis" is abnormal hair growth in unexpected areas.
• Pityriasis is the medical term for dandruff, often caused by a fungus.
• Dandruff may be confused with dry scalp conditions.
• Tinea barbae is the most common fungal infection related to hair services, characterized by itching.
• Pediculosis Capitis is the infestation of the scalp with head lice.

Sociocultural Perceptions

• Baldness is often negatively perceived, associating bald men with decreased success.
• By the age of 35, approximately 40% of both men and women experience some hair loss.
• Finasteride, an oral medication for hair loss, is specifically prescribed for men.

Additional Insights

• Scalp massage does not significantly influence hair growth rates.
• Gray hair is not inherently coarser or more resistant than pigmented hair.
• Hair cross-sections can take on various shapes, indicating diverse hair types.