| eyelid | <anatomy> The cover of the eye; that portion of movable skin with which an animal covers or uncovers the eyeball at pleasure. Source: Websters Dictionary (01 Mar 1998) |
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| upper eyelid | The superior, larger and more mobile of the two eyelids which covers most of the anterior surface of the eyeball, including the cornea, when closed; a portion of the lacrimal gland and the aponeurosis of the levator palpebrae superioris muscle extend into it, the muscle opening the closed eye and providing additional elevation when the gaze is directed upward. Synonym: palpebra superior, upper lid. (05 Mar 2000) |
| lower eyelid | The inferior, smaller and less mobile of the two eyelids; a check ligament from the inferior rectus muscle extends into it, pulling the lid inferiorly when the gaze is directed downward. Synonym: palpebra inferior, lower lid. (05 Mar 2000) |