Now that you know a little about the history of lash enhancement, let’s move on and take an anatomical look at two components of the human body that are of particular interest to the lash technician: the eyelid and the eyelash. You would be forgiven for assuming we might jump straight into an examination of the eyelash given the fact we are studying a course in lash mastery! However, as you’ll soon learn, it is the skin within which the eyelash is housed that provide for some of the eyelash’s most defining characteristics.
In basic terms, the eyelids are folds of skin and tissue connected to a muscle (called the orbicularis occuli) that open and close either voluntarily (i.e. to sleep) or involuntarily (blinking or reflex). The upper eyelid is defined as starting at the eyelid margin (the very edge of the eyelid where the eyelashes grow) and extending to the base of the eyebrow. The lower eyelid again starts at the eyelid margin, and extends to the crease in the skin at the top of the cheek. The primary role of the eyelid is to keep the surface of the eye (cornea) moist, which is achieved by the spreading of tears (a film discharged from the tear duct) every time we blink. Secondary to this, when closed, the eyelids protect the eye from from foreign objects and light.
To understand the peculiarities of the skin of the eyelids, it is helpful to compare it with the skin of the scalp (which is similar to the skin on much of the remainder of the body). The skin on the scalp contains three layers: the epidermis (external), the dermis (middle) and the hypodermis (internal), as you can see in the below diagram.
The skin of the eyelids, however, consists of only two layers: the epidermis (which is much thinner than the epidermis of the scalp) and the dermis. As a result, the skin of the eyelid is much thinner than that on the scalp, and the thinnest of any region of the body at lass than 1mm in thickness.
In terms of how this affects the eyelash (your canvas!), all hair follicles on the human body are rooted in their deepest skin layer, notably the hypodermis on the scalp and the dermis within the eyelid. Consequently, the eyelash follicle is shorter than the scalp hair follicle, resulting in a much shorter and finer hair shaft.
In addition to their relatively short length and fine composition, another defining property of an eyelash is its curved shape, a characteristic present in all ethnicities. The science behind exactly what causes this phenomenon is far too in depth for a lash mastery course (even the most comprehensive and educational course on the net!). However, in basic terms, this curvature is a result of asymmetric (or uneven) cell development in the hair root within the dermis of the eyelid, resulting in the concave (or inner) side of the hair being thicker and the convex (or outer) side of the hair being thinner. The eyelash therefore essentially grows ‘around’ the thicker, more tightly-packed cells on the inside of the curve (or curl).
Finally, while not necessarily a characteristic that will impact your profession as a lash technician (but may come in handy during a trivia night!), one final difference between eyelashes and other hair on the body is the absence of an arrector pili muscle. The arrector pili is an extremely small muscle that attaches to the hair shaft within the dermis and is responsible for the straightening of the hair in response to cold or intense emotions (commonly referred to as goose bumps).
The relative thinness of the skin layer in itself would suggest that the eyelids are a particularly delicate area of the human body. However, the skin of the eyelid also contains a relatively high amount of blood vessels and very little fat compared with other areas of skin. All of these characteristics combined equate to the skin of the eyelids being extremely susceptible to irritation and more prone to allergic reactions. We’ll explore irritations and reactions in detail in Lesson 2.7 Contraindications and contra-actions.