Barbering

Properties of the Hair and Scalp

Hair Structure

Hair is an appendage of the Skin, in the form of a thin, threadlike outgrowth of the skin and scalp. It is composed of fibrous protein known as Keratin. 

Fullgrown hair is divided into two essential parts: the hair root and the hair shaft.

Hair root: the portion of the hair enclosed within the follicle beneath the skin surface.

Hair Shaft: the portion of the hair we see extending above the skin surface.

Thier are five main structures of a hair root.

• Hair Follicle: the tube-like depression or pocket in the skin or scalp that contains the hair root
• hair bulb: lowest part of a hair strand; the thickened, club-shaped structure that forms the lower part of the hair root.
• dermal papilla: a small, cone-shaped elevation located at the base of the hair follicle that fits into the hair bulb
• arrector pili muscle: the small, involuntary muscle in the base of the hair follicle
• sebaceous glands: the oil glands in the skin that are connected to the hair follicles

Their are three main layers or Structures of Hair Shaft

• Hair cuticle: outermost layer of hair; consisting of a single, overlapping layer of transparent, scale-like cells that look like shingles on a roof.
• cortex: middle layer of the hair; a fibrous protein core formed by elongated cells containing melanin pigment
• medulla: innermost layer of the hair that is composed of round cells; often absent in fine and naturally blond hair.

Hair growth

Vellus hair or lanugo: the short, fine, unpigmented, downy hair

Terminal Hair: The long, coarse hair found on the scalp, legs, arms, and bodies

Hair growth occurs in cycles consisting of three phases:

• Anagen (growth phase): Most hair is growing at any given time. Each hair spends several years in this phase.
• Catagen (transitional phase): Over a few weeks, hair growth slows and the hair follicle shrinks.
• Telogen (resting phase): Over months, hair growth stops and the old hair detaches from the hair follicle. A new hair begins the growth phase, pushing the old hair out.

Chemical Composition of Hair

Keratinization: process by which newly formed hair cells in the hair bulb mature, fill with keratin, move upward, lose their nucleus and die

Keratin: a fibrous protein that grows from cells originating within the hair follicle

COHNS elements: Major elements that make up hair: Carbon, Oxygen, Hydrogen, Nitrogen, and Sulfur

amino acids: units that are joined together end-to-end like pop beads by strong, chemical peptide bonds to form the polypeptide chains that comprise proteins

peptide bond: also known as end bond; chemical bond that joins amino acids to each other, end-to-end, to form polypeptide chain

polypeptide chain: a long chain of amino acids linked by peptide bonds

proteins: long, coiled complex polypeptides made of amino acids

Side Bonds of the cortex: link the polypeptide chains (long chain of amino acids linked together by peptide bonds) together; responsible for the strength and elasticity of human hair

• hydrogen bond: weak, physical cross-link bond that is easily broken by water or heat
• salt bond: weak, physical cross-link bond that is broken by alkaline or acidic solutions
• disulfide bond: strong, chemical side bond; can be broken by extreme heat, some high-temp styling tools, permanent waves and chemical relaxers