Hair and Scalp Care 1 HSA3400

The study of the hair is called Trichology

The chief purposes of hair are adornment and protection. Hair is composed mainly of a protein called keratin.

Full-grown human hair is divided into two principal parts: The Root – which is the portion of the hair located beneath the skin’s surface; this is the portion of the hair enclosed within the follicle. The Hair Shaft – is the portion of the hair structure extending above the skin’s surface.

Structures associated with the hair root are the follicle, bulb, and papilla. The follicle is a tube-like depression in the scalp or skin that encases the hair root. The bulb is a club-shaped elevation located at the bottom of the hair root. The papilla is a cone-shaped elevation located at the bottom of the hair follicle and fits into the hair bulb. The papilla contains a rich blood and nerve supply that contributes to the growth and regeneration of the hair.

Structures associated with the hair follicles are the arrector pili and sebaceous gland. The arrector pili is an involuntary muscle attached to the underside of the hair follicle. The sebaceous is an oil gland connected to the follicle. It produces sebum (oil) that keeps the skin soft and supple.

The layers of the hair are: Cuticle – outside layer composed of overlapping scales that protect the inner layers. Cortex – inner layer which gives strength and elasticity. The cortex also contains pigment called melanin. Medulla – innermost layer that determines the thickness of individual strands of hair. The medulla may be absent in fine hair.

Location We have hair over most of our bodies except for the palms of the hands, soles of the feet, the lips, and a few other very small areas. There are two types of hair: Languo – all over the body, it is fine, un-pigmented hair. Terminal – found on the scalp, face, and extremities; it is coarser hair.

What is hair texture?

TEXTURE It is the diameter of the hair. Fine is smaller and thinner in diameter. Medium is larger that fine hair. Coarse is larger than medium hair. There are two structures that influence the diameter of the hair: the medulla and the cuticle. Texture is very important when selecting products.

Porosity refers to the amount of moisture that can be absorbed by the cuticle layers. Elasticity refers to the hair’s ability to stretch without breaking and then return to its original form. Density refers to the number of hairs per square inch.

Cycles of Growth The first hair appears in the sixth or seventh week after conception. All human growth cycles differ from one region of the body to another. Scalp hair grows 2-5 years, hair on the trunk, limbs, etc. occurs 4-6 months. The three cycles of growth are Anagen, Catagen, and Telogen (A.C.T.) Anagen – first period when the hair bulb stretches itself out into the follicle. The second period is when keratin is being synthesized in the follicle (2-5 years). Catagen – hair growth slows and club hairs form. Keratinization does not take place during this stage. Telogen – resting period that continues until the next anagen stage begins, it lasts about 3-4 months.