Normal eyelashes grow in the front lip of eyelid margin, developed from the surface ectodermal epithelium, and arranged in 2 ~ 3 rows, showing short and curved coarse hair. Eyelashes have the functions of avoiding light, shielding dust, preventing foreign objects from entering the eyes and beautifying the eyes. Slender, black and upturned eyelashes play an important role in modifying people's appearance beauty. There are a large number of eyelashes on the upper eyelid, ranging in length from 100 to 150, with an average length of 8- 12mm. When eyes are open and closed, the angle of upper eyelid eyelashes is 1 10 ゜ ~ 130 ゜. There are 50 ~ 80 eyelashes in the lower eyelid, with an average length of about 6 ~ 8 mm When the eyelashes of the lower eyelid are open, they are 100 ~ 120 ゜.
Hairy roots of eyelashes live deep in connective tissue and muscle, where there are abnormal sweat glands and sebaceous glands, and their ducts open in the eyelash sac. There are many small holes in the posterior lip of eyelid, which are the openings of meibomian gland ducts, and meibomian gland itself is located in meibomian. The abnormality of eyelash inclination angle can be caused by the change of eyelash growth angle or eyelid disease. There are often pain, jealousy, tears, fear of light, persistent foreign body sensation, and increased eye secretions. Many children don't want to look up, and they don't want to cooperate with flashlights or slit lights for fear of light.
The above is the knowledge about eyelashes, and I hope it will help everyone.