Cilia Incarnata

Eyelashes develop from ectoderm between weeks 22 and 26 of gestation. Although the length varies from person to person, they do not grow beyond a certain length and then fall off by themselves. They generally do not need trimming unless there is excessive growth (trichomegaly). If a person pulls a lash out, it takes about 8 weeks to grow back. Eyelash hair is not affected by puberty. Eyelash follicles are 2.4-mm deep in the upper lid and 1.4 mm in the lower lid. There are more active lash follicles in the upper lid compared to the lower lid (41% vs. 15%). The function of eyelashes is to protect the eyes from particulate matter. They are also highly innervated, making them sensitive (have been compared to cat's whiskers) to touch and again help protect the eyes. The human lower eyelid has 75 to 80 lashes in three to four rows, whereas the upper eyelid has 90 to 160 lashes scattered on five to six rows. Each lash has a hair shaft that extends outside the skin, a root that is under the skin, and a bulb that is the enlarged terminal portion. The inferior portion of the bulb is in direct contact with the dermal papilla, which brings key mesenchymal-epithelial interactions in follicle cycling. Unlike the scalp, which has the epidermis, dermis, and hypodermis, eyelid skin is thinner with only the epidermis and dermis. Lash follicles also do not have arrector pili muscles which straighten the hair in response to cold or intense emotions. is the misdirection of eyelashes whereby they grow under the skin through to the surface or posteriorly to the conjunctival surface instead of emerging normally from the eyelid margin. Two types are recognized: 1. Cilium incarnatum internum. 2. Cilium incarnatum externum  . Cilium is a neuter noun whose plural is cilia or cilii). Incarnata is the neuter plural of incarnatus, which is the perfect passive participle of incarno, which means "to make or become flesh." Incarnatum is the first supine of incarno.  Internum is the adjective neuter form meaning "internal" or "inward." Externum is the adjective neuter form meaning "external" or "outward." The word incarno, from which incarnata and incarnatum are derived imply inflamed, or red and fleshy, as in the Crimson Clover named incarnatum because of its deep crimson color. In the conditions under discussion, there is no inflammation or redness of the eyelid in either of the conditions, and cilium incarnatum internum only causes irritation of the cornea and sometimes a conjunctival inflammation, but no fleshy or inflamed appearance. With that in mind, a more accurate description of these two conditions, derived from the Latin, would be as follows: literally meaning lash growing inward  literally meaning lash growing outward.