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Sclera
The sclera, also known as the white of the eye, is the opaque, fibrous, protective, outer layer of the eye containing mainly collagen and some elastic fiber. In humans, the whole sclera is white, contrasting with the coloured iris, but in other mammals the visible part of the sclera matches the colour of the iris, so the white part does not normally show. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow.
The human eye is relatively rare for having an iris that is small enough for its position to be plainly visible against the sclera. This makes it easier for one individual to infer where another individual is looking, and the cooperative eye hypothesis suggests this has evolved as a method of nonverbal communication.
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Conjunctiva
The conjunctiva lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with goblet cells, and also stratified columnar epithelium. The conjunctiva is highly vascularised, with many microvessels easily accessible for imaging studies.
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Sclera (noun)
The white of the eye. It is the tough outer coat of the eye that covers the eyeball except for the cornea.
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Conjunctiva (noun)
A clear mucous membrane that lines the inner surface of the eyelid and the exposed surface of the eyeball or sclera.
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Sclera (noun)
the white outer layer of the eyeball. At the front of the eye it is continuous with the cornea.
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Conjunctiva (noun)
the mucous membrane that covers the front of the eye and lines the inside of the eyelids.