Anatomy of the eyelashes
The eyelashes, Latin Ciliae, are appendages of the skin in mammals and humans. They are in the form of curved hairs on the edge of the upper and lower eyelids of the eye and cover them completely as a so-called lash line. They form two to four rows and serve to protect the sensitive eye.
The eyelashes belong to the bristle hairs. In their shape they are short, rigid and curved. The number of lashes per eye varies between 50 and 250 lashes.
In order not to restrict vision, they are curved upwards on the upper eyelid and downwards on the lower eyelid. On the upper eyelid there are more (approx. 200) and longer (approx.
10 mm) lashes, on the lower eyelid they are shorter (approx. 7 mm) and less numerous (approx. 75).
The eyelashes originate from the hair root. This is surrounded by sebaceous glands, the Zeiss and Meibom glands. However, unlike most other hairs in the body, eyelashes do not have a muscle that can erect them, the so-called Musculus erector pili.
The length of the eyelashes on the upper eyelid differs from that on the lower eyelid: on the top are the longer eyelashes with a length of about 8 to 12mm. On the lower eyelid they are only 6 to 8mm long. The life span of the eyelashes is relatively short: after 100 to 150 days they will be pushed off the skin of the eye and replaced by new eyelashes.
The growth period of new eyelashes is about 10 weeks. If the lashes are cut or torn off, the body compensates by regrowth. The lashes receive their nutrients, such as fat, through their root-like anchoring on the eyelids, where sebaceous and sweat glands are located.
This keeps the eyelashes supple. As a rule, the eyelashes have the same color as the head and body hairs. If the lashes are touched unexpectedly, the eye is closed reflexively.
The eyelashes interlock with each other and form a kind of catch cage. This protects the eye from possible foreign bodies. This takes place within about 250 milliseconds. Various glands at the base of the eyelashes lubricate the lashes.
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