2.2 Skin & Hair Structure, Growth, and Disorders

Section 2.2: Skin & Hair Structure, Growth, and Disorders

Barbers must possess a thorough understanding of the skin and hair to perform chemical services, style hair, and recognize scalp and skin disorders. Analyzing the condition of the client’s hair and skin determines the choice of products and techniques, while identifying contagious conditions prevents the spread of infectious disease in the shop.

Structure of the Skin

The skin is the largest organ of the body, acting as a barrier against pathogens, regulating temperature, and sensing touch. It is divided into three main layers: the epidermis, the dermis, and the subcutaneous tissue.

1. Epidermis (Cuticle or Scarf Skin)

The epidermis is the outermost, protective layer of the skin. It contains no blood vessels but has many small nerve endings. It consists of five distinct layers:

• Stratum Corneum (Horny Layer): The outer layer that we see. It is made of scale-like cells that are continually shed and replaced. These cells contain keratin, a fibrous protein that is also the principal component of hair and nails.
• Stratum Lucidum (Clear Layer): The clear, transparent layer under the stratum corneum, consisting of small cells through which light can pass. This layer is most prominent on the palms of the hands and soles of the feet.
• Stratum Granulosum (Granular Layer): Consists of cells that look like distinct granules and are filled with keratin. These cells are dying as they are pushed to the surface.
• Stratum Spinosum (Spiny Layer): The layer where the process of skin cell shedding begins.
• Stratum Germinativum (Basal Layer): The deepest layer of the epidermis. It is the active growth layer where cells undergo mitosis and contains melanocytes, which produce the pigment melanin that determines skin color.

2. Dermis (True Skin or Corium)

The dermis is the underlying, inner layer of the skin. It is highly sensitive and contains blood vessels, lymph vessels, nerves, sweat glands, oil glands, hair follicles, and arrector pili muscles. It consists of two layers:

• Papillary Layer: The outer layer of the dermis, located directly beneath the epidermis. It contains small, cone-shaped projections called dermal papillae, which contain tactile corpuscles (nerve endings sensitive to touch) and loop capillaries.
• Reticular Layer: The deeper layer of the dermis that supplies the skin with oxygen and nutrients. It contains fat cells, blood vessels, hair follicles, sebaceous (oil) glands, and sudoriferous (sweat) glands.

3. Subcutaneous Tissue (Adipose or Subcutis)

Located beneath the dermis, subcutaneous tissue is a layer of fatty tissue that gives smoothness and contour to the body, contains fats for energy, and acts as a protective cushion for the outer skin layers.

Anatomy of the Hair Follicle

Hair is an acidic protein filament growing from a follicle in the dermis. The hair structure is divided into the hair root (the portion below the skin surface) and the hair shaft (the portion projecting above the skin).

The structures of the hair root include:

• Hair Follicle: A tube-like depression or pocket in the skin or scalp that contains the hair root.
• Hair Bulb: The lowest part of the hair strand; a 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. It contains the blood and nerve supply that provides the nutrients needed for hair growth.
• Arrector Pili Muscle: A tiny, involuntary muscle fiber in the skin inserted at the base of the hair follicle. Strong emotions or cold cause it to contract, making the hair stand straight up (goosebumps).
• Sebaceous Glands: Oil glands connected to the hair follicles that secrete sebum, a fatty or oily substance that lubricates the skin and hair.

Hair Growth Cycles

Hair growth occurs in repeating cycles consisting of three phases:

1. Anagen Phase: The active growth phase. Approximately 90% of scalp hair is in this phase at any given time. It lasts from two to six years, during which hair grows about half an inch per month.
2. Catagen Phase: The brief transition period between the growth and resting phases. The follicle shrinks, the hair bulb detaches from the dermal papilla, and the hair becomes a club hair. This phase lasts for one to two weeks.
3. Telogen Phase: The resting and shedding phase. The follicle remains inactive for three to six months until the hair is shed or pushed out by a new hair growing underneath. Approximately 10% of scalp hair is in the telogen phase.

Hair and Scalp Analysis

Before any service, a barber must analyze four critical characteristics of the hair:

• Texture: The thickness or diameter of the individual hair strand (classified as coarse, medium, or fine). Coarse hair requires stronger chemicals during services, while fine hair is easily damaged.
• Porosity: The ability of the hair to absorb moisture. Low porosity hair has a tight cuticle that resists liquid penetration, requiring alkaline solutions. High porosity hair has a raised cuticle that absorbs liquids rapidly but loses moisture quickly, requiring lower pH products.
• Elasticity: The ability of the hair to stretch and return to its original length without breaking. Normal wet hair stretches up to 50% of its original length, while dry hair stretches 20%. Low elasticity indicates damaged or brittle hair.
• Density: The number of individual hair strands per square inch of scalp (classified as thin, medium, or thick/dense). This determines the volume of hair the barber will manipulate.

Common Skin and Hair Disorders

Barbers must recognize skin and scalp conditions to determine if a service can proceed or if the client should be referred to a physician.

Scalp Disorders (Dandruff)

Dandruff is caused by a naturally occurring fungus called Malassezia.

• Pityriasis Capitis Simplex: Classic dry dandruff, characterized by scalp irritation, itchy skin, and small, flaky scales.
• Pityriasis Steatoides: A more severe form of dandruff characterized by an accumulation of greasy or waxy scales mixed with sebum that stick to the scalp in crusts.

Hair Loss (Alopecia)

• Androgenetic Alopecia: Male pattern baldness, caused by genetics and hormonal changes (conversion of testosterone to DHT). It results in the progressive shrinking of terminal hairs into fine vellus hairs.
• Alopecia Areata: An autoimmune disorder where the immune system attacks hair follicles, causing hair to fall out in patches, leaving round, smooth bald spots.

Skin Lesions

A lesion is a mark on the skin that may indicate injury or disease.

• Primary Lesions (Flat or Raised): Include the macule (flat spot like a freckle), papule (small elevation containing no fluid), and pustule (an inflamed papule containing pus).
• Secondary Lesions (Accumulated material or skin damage): Include the scale (flaky epidermal cells like dandruff), fissure (a chapped lip or cracked hand skin), and crust (scab on a sore).