2.1 – Hair Facts for Electrolysis

Step 1 Hair facts for electrolysis 

In order to understand the way in which electrolysis works, and to select suitable candidates for  treatment you need to understand in some depth the histology of the hair follicle and surrounding  tissues, how hair grows and how it reacts to different types of hair removal. Hair is a sensitive,  tactile organ which is capable of increasing awareness through sensation and touch. It grows at an  angle to the surface, so that it follows the natural contours of the body above the surface. Let’s  look at the types of hair first. 

Hair Types 

There are three different types of hair found on the human body: lanugo, vellus and terminal. 

Lanugo hair is formed on the foetus whilst in the womb, usually shed around the seventh or eight  month, but can be shed after birth. Hair that is being lost from the scalp due to baldness reverts to  this primary type before disappearance. This hair is fine and soft without a medulla and usually  unpigmented. Lanugo may reappear under conditions of starvation, for example, in someone suf fering from anorexia. 

Vellus is fine soft hair which covers most of the body, except the palms, soles, lips and genital  areas. This type of hair is non-pigmented, fine, downy and soft. It has no medulla, and has a shal low follicle, small blood supply and is usually less than 2cm in length and under 30µm in cross sectional diameter. 

Terminal hair is longer, pigmented, varies in shape and usually exceeds 40µm in cross-sectional  diameter. It is this hair that both men and women sometimes find superfluous and seek a means of having  it removed. 

Superfluous hair is a general term used to describe any unwanted hair and is what clients seek to have  removed through temporary or permanent hair reduction treatments. 

There are two types of terminal hair: 

• asexual hair – eyebrows, lashes and the hair on the head. These hairs are terminal in nature from  birth. Differences in these hairs are not related to hormones. 
• sexual hair – other areas of hair, typically the pubic area, underarm, legs and arms, face, chest and  abdomen, back and shoulders. These are vellus at birth and change to terminal under hormonal  influence. 

Structural and Cellular Features of a Hair Follicle 

Secondly, let’s look at the structure of a typical terminal hair and the unit that contains it – the hair sheath  and associated structures. Together they are called the pilosebaceous unit. 

The pilosebaceous unit (pilo = hair, sebum = grease) consists of the hair follicle (the hair sheath  and the hair), and the oil-producing or sebaceous gland. The sebaceous gland produces sebum,  an oily compound that lubricates our skin and hair. The gland discharges the sebum through the  pilosebaceous duct into the upper part of the hair follicle. In the axilla and the perineum or ano genital area apocrine glands are also associated with the pilosebaceous unit. The external auditory  canal (ear canal) and areola (nipple area) of mammary skin contains apocrine glands in more  limited numbers and they are rarely activated at these sites. Apocrine glands develop from and are  associated with the hair follicles and their ducts open into the upper portion of the hair shaft. These  glands produce sweat. 

The pilo-sebaceous unit also contains a bundle of smooth muscle extending from the epidermis to  the hair follicle. This muscle is called the arrector pili muscle and when it contracts it pulls the hair  from its normal position lying at an angle to the skin into a vertical position. The muscle contracts in  response to cold or fright. In fright the upright hair makes us look larger and thus more frightening – not unlike a cat’s tail when it is alarmed. In cold it is what causes “goose bumps”. This is an attempt  to retain body heat by providing us with a thicker layer of “fur” – no longer much use in humans as  our hair cover is minimal.

The inferior segment includes the deepest part of the hair follicle and extends to the bulge (the  part just below the arrector pili muscle attachment). It contains the hair bulb or matrix with its ger minative matrix cells and melanocytes. The hair bulb surrounds a highly vascularised connective  tissue called the dermal papilla. The cells in the matrix divide and form the hair. The cells divide  

rapidly – about every 23 to 72 hours. This is one of the fastest division rates in the body. The isthmus extends from the bulge to the opening of the sebaceous duct. 

The infundibulum extends from the sebaceous duct opening to the epidermal surface. Note:  as the hair follicle is angled the bulge lies on the deeper aspect of the follicle. 

The hair follicle is composed of the external and internal root sheaths and the hair shaft. When  looking at a vertical section of the hair follicle it will display an external sheath, an internal sheath and  a hair shaft. 

The external sheath is formed by the basal and spinosum layers of the epidermis creating a  downward structure. Towards the top of sheath, all the epidermal layers are present, whereas  towards the bottom of the sheath, only the stratum basal is present. At the level of the infundibu-lum  this external sheath is continuous with the epidermis. This layer never totally regresses and gives  rise to the new hair in the next growth cycle. It contains melanocytes, Langerhan cells, mast cells,  Merkel cells and neuronal stem cells. All these cells operate within the hair follicle and form a  reservoir from which the epidermis regenerates after injury. 

The internal sheath provides rigid support for the growing hair shaft. It tapers off above the  bulge and does not grow beyond this level. The growing hair is shaped and curved by the internal  sheath – this is the part that determines the shape of the hair. 

The hair shaft is the part of the hair that we can see growing above the skin and which reaches down into  the hair sheath. There are three main parts to the terminal hair shaft – the medulla, the cortex and the  cuticle.