Cosmetology Chapter 7 & 8 Red Milady Textbook

Trichology

The study of hair, including its diseases and care.

Hair Root

Located below the epidermis

Hair Shaft

Projects above the epidermis.

Hair follicle

A tube-like structure in the skin or scalp that surrounds the hair root and anchors the hair in the skin.

Hair bulb

Located at the base of the follicle… has a ___ shape and contains living cells that will form the hair strand.

Dermal Papilla

Also known as hair _____, is a cone-shaped elevation at the base of the hair bulb.

• Contains blood vessels that supply nutrients that allow hair to grow.

Hair cuticle

The hair’s outermost layer.

• Formed from cells that resemble shingles on a roof; protects the cortex.

Amino Acids

Form the building block of protein; link together end to end and like pop beads by strong, chemical peptide bonds (end bonds) to form the polypeptide chains that comprise proteins.

Anagen phase

Also known as the growth phase, the hair phase is the phase during which new hair is produced.

Catagen phase

The brief transition period between the growth and resting phases of the hair follicle signals the end of the growth phase.

COHNS elements

Five elements - Carbon, Oxygen, Hydrogen, Nitrogen and Sulfur —— make up the human hair, nails, skin, and tissue.

Cortex

Fibrous protein layer of the hair; responsible for the strength, elasticity, and color of the hair.

Cowlick

Hair that grows straight up or at a different angle than the other hair; usually more noticeable at the crown of the head. noticeable

Cysteine

An amino acid with Sulfur (S) atom that joins together two peptide strands

Disulfide bond

A strong chemical side bond that joins the sulfur atoms of two neighboring cysteine amino acids to create one cysteine, which joins together two polypeptide strands like rungs on a ladder.

Eumelanin

Consists of brown and black pigment and is the predominant pigment in black and brunette hair.

Hair density

Measures the number of individual hair strands on 1 square inch (2.5 square centimeters) of scalp.

Hair elasticity

The hair’s ability to stretch and return to its original length without breaking.

Hair porosity

Refers to the hair’s ability to absorb moisture.

Hair stream

Hair flowing in the same direction, resulting from follicles sloping in the same direction.

Hair texture

Thickness or diameter of an individual’s hair strand.

Hydrogen Bond

A weak physical cross-link side bond that is easily broken by water or heat.

Keratinization

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

Lanthionine bonds

Bonds are created when disulfide bonds are broken by hydroxide chemical hair relaxers.

Lanugo hair

Short, fine hair that covers a fetus and generally sheds within a few weeks of birth.

Medulla

Innermost layer found in coarse hair and beard hair; known as hair’s pith or core; absent in fine hair.

Melanin

Tiny grains of pigment in the cortex that give natural color to the hair.

Peptide bond

Also known as an end bond; chemical bond that joins amino acids to each other, end-to-end, to form a polypeptide chain.

Pheomelanin

Yellow to red pigment found in natural blonde to red shades of hair.

Polypeptide chain

A long chain of amino acids linked by peptide bonds.

Salt bond

A weak physical cross-link side bond between adjacent polypeptide chains that is broken by changes in pH.

Side bonds

Bonds that cross-link polypeptide chains and are responsible for the extreme strength and elasticity of human hair; account for about one-third of hair’s overall strength.

Telogen phase

Also known as the resting phase; the final phase in the hair cycle that lasts until the fully grown hair is shed.

Terminal hair

Long, coarse, pigmented hair found on the scalp, legs, arms, and body.

Vellus hair

Short, fine, unpigmented hair that appears on the body, often referred to as peach fuzz.

Wave pattern

Amount of movement or shape of the hair strand; described as straight, wavy, curly, or coily.

Whorl

Occurs when hair leaves the follicles at an angle; hair grows in a circular pattern on the crown of the head.