eyelid


eyelid
/uy"lid'/, n.
the movable lid of skin that serves to cover and uncover the eyeball.
[1200-50; ME; see EYE, LID]

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      movable tissue, consisting primarily of skin and muscle, that shields and protects the eyeball from mechanical injury and helps to provide the moist chamber essential for the normal functioning of the conjunctiva and cornea. The conjunctiva is the mucous membrane that lines the eyelid and covers the visible portion of the eyeball except the cornea (the transparent part of the eyeball that covers the iris and the pupil). Each eyelid contains a fibrous plate, called a tarsus, that gives it structure and shape; muscles, which move the eyelids; and meibomian (or tarsal) glands, which secrete lubricating fluids. The lids are covered with skin, lined with mucous membrane, and bordered with a fringe of hairs, the eyelashes. The lids move through the action of a circular lid-closing muscle, the orbicularis oculi, and of the lid-raising muscle, the levator of the upper lid. Impulses for closing come by way of the facial (seventh cranial) nerve, and for opening by way of the oculomotor (third cranial) nerve. The lid borders are kept lubricated by an oily secretion (called sebum) of the meibomian glands. This secretion forms part of the tear film and reduces evaporative tear loss.

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Universalium. 2010.

Look at other dictionaries:

  • Eyelid — Eye lid , n. (Anat.) The cover of the eye; that portion of movable skin with which an animal covers or uncovers the eyeball at pleasure. [1913 Webster] …   The Collaborative International Dictionary of English

  • eyelid — mid 13c., from EYE (Cf. eye) (n.) + LID (Cf. lid) …   Etymology dictionary

  • eyelid — ► NOUN ▪ each of the upper and lower folds of skin which cover the eye when closed …   English terms dictionary

  • eyelid — [ī′lid΄] n. [ME eielid, eien lidd: see EYE & LID] either of the two movable folds of flesh that cover and uncover the front of the eyeball …   English World dictionary

  • Eyelid — Palpebrae redirects here. For the levator palpebrae, see levator palpebrae superioris muscle. Eyelid Upper and lower eyelids Latin palpebra inferior, palpebra superior …   Wikipedia

  • eyelid — noun ⇨ See also ↑eyelid ADJECTIVE ▪ lower, upper ▪ closed, half closed ▪ drooping, heavy, hooded VERB + EYELID …   Collocations dictionary

  • eyelid — n. 1) drooping eyelids 2) (misc.) without batting an eyelid (esp. BE) ( while remaining calm ) (AE has without batting an eyelash) * * * [ aɪlɪd] drooping eyelids (misc.) without batting an eyelid (AE has without batting an eyelash; while… …   Combinatory dictionary

  • eyelid — UK [ˈaɪˌlɪd] / US noun [countable] Word forms eyelid : singular eyelid plural eyelids one of the two pieces of skin that cover your eye when it is closed …   English dictionary

  • eyelid — One of the two movable folds covering the front of the eyeball when closed; formed of a fibrous core (tarsal plate) and the palpebral portions of the orbicularis oculi muscle covered with skin on the …   Medical dictionary

  • eyelid — eye|lid [ˈaılıd] n a piece of skin that covers your eye when it is closed ▪ His eyelids began to droop (=close, because he was sleepy) . ▪ The room spun. Her eyelids fluttered (=moved up and down quickly) and she fainted. →not bat an eyelid at… …   Dictionary of contemporary English


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