eyelid

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 superficial, anterior surface and lined with conjunctiva on the deep, posterior surface; rapid contraction of the contained muscle fibers produces blinking; they each have fixed (orbital) and free margins, the latter separated centrally by the palpebral fissure, united at the lateral and medial palpebral commissures, and bearing eyelashes, the openings of tarsal and ciliary glands and (medially) the lacrimal puncta.palpebra [NA], blepharon, lid;
lower e. the inferior, smaller and less mobile of the two e.'s; a check ligament from the inferior rectus muscle extends into it, pulling the lid inferiorly when the gaze is directed downward.palpebra inferior [NA], lower lid;
third e. plica semilunaris conjunctivae (2)
upper e. the superior, larger and more mobile of the two e.'s 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.palpebra superior [NA], upper lid;

 

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