Milady Chapter 11: Hair & Scalp Properties

Properties of the Hair & Scalp

• Trichology: Refers to the study of hair, encompassing its structure, function, and disorders.

• Amino Acids: The body produces 11 out of 20 amino acids that constitute hair; the remaining essential amino acids must be obtained through diet.

• Hair Structure: A hair strand is principally divided into two parts: the hair root and the hair shaft.

• Hair Follicle: A tube-like depression in the skin or scalp that encases the hair root.

• Dermal Papilla: A club-shaped elevation at the bottom of the hair follicle that plays a key role in hair growth.

• Arrector Pili Muscle: An involuntary muscle that contracts to cause hair to stand up, often in response to cold or fear.

• Sebaceous Glands: Oil glands in the skin that are connected to hair follicles, providing moisture to the hair.

• Hair Layers: The hair shaft consists of three layers - the cuticle (outer layer), cortex (middle layer), and medulla (innermost layer).

• Melanin: Found in the cortex, it consists of tiny pigment grains that determine hair color.

• Types of Hair: Terminal hair is long, coarse, and pigmented, found on the scalp, legs, arms, and body.

• Hair Growth Phases: Hair follicles cycle through three phases: Anagen (growth), Catagen (transitional), and Telogen (resting).

• Hair Texture: Defined by its thickness or diameter, determining the overall feel and appearance of the hair.

• Porosity: Refers to the hair's ability to absorb moisture, crucial for maintaining hair health.

• Elasticity: Describes the hair's ability to stretch and return to its original form without breaking, indicating its strength.

• Alopecia Areata: A type of hair loss characterized by round or irregular patches, occurring without inflammation.

• Whorl: Describes hair that forms in a circular pattern, which can affect styling and appearance.

• Trichorrhexis Nodosa: A condition of dry, brittle hair featuring nodular swellings along the hair shaft.

• Polypeptide Bond: The bond that connects amino acids to form the proteins that comprise the hair structure.

• Element Composition: Normal hair is made up of various elements:

  • Carbon: 51%
  • Oxygen: 21%
  • Hydrogen: 6%
  • Nitrogen: 17%

• Keratinization: The process where newly formed hair cells fill with fibrous protein, lose their nucleus, and die to form the hair structure.

• Ionic Bond: A type of bond easily broken by strong alkaline or acidic solutions, affecting hair’s strength and integrity.

• Melanin Function: Pigments in the cortex that provide natural hair color, with types such as pheomelanin contributing to lighter shades (red, yellow, blond).

• Wave Pattern: Describes the hair strand's shape, categorized as straight, wavy, curly, or extremely curly.

• Hair Density: Indicates the number of individual hair strands per square inch on the scalp, contributing to volume.

• Vellus Hair: Short, fine, unpigmented hair, often referred to as "peach fuzz," covering much of the body.

• Minoxidil: A topical medication applied to the scalp to stimulate hair growth, used twice daily.

• Finasteride: An oral prescription medication for hair loss, particularly effective for men.

• Canities: The technical term for gray hair, resulting from decreased melanin production.

• Trichoptilosis: Refers to split ends, a common issue indicating hair damage.

• Monilethrix: The technical term for beaded hair, a condition involving irregularities in hair texture.

• Tinea Capitis: A fungal scalp condition marked by red papules or spots at the openings of hair follicles.

• Pediculosis Capitis: A contagious condition caused by lice infestation, leading to itching and discomfort.

• Furuncle: An infection of a hair follicle caused by staphylococcus bacteria, resulting in pain and inflammation.