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Hair and Eyelash anatomy

Hair Anatomy:

Hairs are dead structures that are made of a hardened protein called keratin and grow out from follicles. Most of the body is covered with hairs, with the exception of the palms of the hands and the soles of the feet. They help to keep the body warm and are also a form of protection. The eyelashes prevent substances from entering the eyes, and the hairs that line the nose and ears help to trap dust and bacteria.

Hair Growth Definitions

There are two main types of hair:

  • Vellus (lanugo when found on the foetus)
  • Terminal

Lanugo Hair

Very soft, downy hair formed on the foetus usually by the 5th or 6th month. It is shed soon after birth and replaced by vellus hair. Its characteristics are like vellus hair.

Vellus Hair

Like lanugo, but not quite so fine. Very soft, short (rarely exceeds 2cm in length), downy hair which is barely visible as it is not pigmented. It lacks a medulla and does not have an Arrector pili muscle.

Vellus hair is found all over the body, apart from:

  • Palms
  • Soles
  • Lips
  • Nipples
  • Terminal joints of the fingers
  • Regions occupied by terminal hair

 

Vellus hair lie very shallowly in the skin and the growth rate is very slow as they have quite an ineffective papilla and matrix with a very poor blood supply.

The function of primary hair is to aid in the evaporation of perspiration from the body.

Terminal Hair

This is coarse, visible hair usually pigmented (except in ageing clients when greying occurs and typically found at the following body sites:

  • Scalp
  • Brows
  • Lashes
  • Nostrils
  • Ears
  • Axillae
  • Pubic region
  • Legs
  • Arms
  • Beard (males)
  • Chest (males)

Terminal hair is divided into:

  • Asexual: genetic and present at birth (i.e. scalp, brows, lashes and, to a lesser extent, forearms and legs in both sexes)

 

  • Ambisexual: hair that develops at puberty in both sexes. It is hair that is influenced by hormonal activity (i.e. axillae, pubic hair, lower limbs and abdomen in both sexes)

 

  • Sexual: beard, moustache, nasal, ear, back and chest hair. Influenced by male androgen hormones, the principal one being testosterone. Due to testosterone levels being higher in men, their sexual hair is more pronounced

 

Unlike vellus hair, terminal hair tends to lie deeply in the skin with a very rich blood supply to the papilla. Often, they possess a natural curve. Some terminal hairs increase in thickness and number with age, particularly brows and edge of ears of older men.

The function of terminal hair is protection:

  • The hair of the lashes is controlled by a very sensitive reflex action which prevents foreign objects entering the eye

 

  • The hair of the nostrils serves as protection against micro-organisms entering the body

Terminal hair (except lashes, brows, nose, ear, axillae and pubic) have an Arrector pili muscle and so demonstrates the characteristic goose bumps when cold or afraid

The three primary layers of hair are the:

  • Cuticle
  • Cortex
  • Medulla

 

Eyelash Anatomy:

Each eyelid contains eyelashes and each is anchored into a root hair plexus. Unlike normal hairs, this gives eyelash hairs extra sensitivity, meaning they can cause the eye to reflexively snap closed if a foreign body reaches the eye. Eyelashes tend to graduate in length, being longest towards the centre of the eye and shorted towards the outer corners.

From a lash technician’s perspective, it’s important to note that the lashes on the upper lids and lower lids are actually quite different from one another. Upper lid lashes tend to be thicker, longer, more numerous and curve in an upwards direction. The lashes on the lower lid, by contrast are shorter and can have little or no curve.

Each lash grows between 7 – 9 mm in length in distinct rows along the lid. There are 90 -160 lashes on the upper lid and 70 – 85 on the lower eyelid. The upper eyelid lashes are also much coarser than the lower eyelid.

The eyelash grows for approximately 30 days and then rests for the rest of its life. The average life span of an eyelash is approximately 3 months/12 weeks, i.e. the eyelash grows for approximately one month, then rests for approximately two months before it falls out.

Every eyelash hair consists of three main regions and three primary layers. The main regions are the roots, shaft and tip.

Root:

The part that grows in the follicle. It is the widest part of the eyelash.

Shaft:

The middle length of the eyelash. It is where the eyelash begins to taper

Tip:

The end of the eyelash, the point at which it is at its thinnest.