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 Encyclopedia - Conjunctiva

What are the parts of conjunctiva?
What is the function of conjunctiva?

The conjunctiva is a transparent mucous membrane that covers the sclera, which is the white of the eye (See Anatomy of the Eye). The conjunctiva lines the inner surfaces of the eyelids. Comprised of many small blood vessels, the tiny secretory glands in the conjunctiva produce tear film that lubricates and protects the eye while it moves in its socket. When the eye is irritated, injured, or infected, these blood vessels dilate making the white part of the eye look red.

Bacteria and virus can inflame the conjunctiva, often leading to a condition called conjunctivitis. Although the conjunctiva is normally a tough, resilient tissue, in cases of ocular trauma, it may be lacerated with sharp or pointed objects such as fingernails, tree branches, or the edge of a piece of paper.

What are the parts of the conjunctiva?

The conjunctiva is composed of three sections or regions:

  • the palpebral -- which lines the under-surface of the eyelids,
  • the bulbar -- which covers the front, external eyeball, and
  • the fornix -- which forms the junction between the eyelid and eyeball.

The palpebral is moderately thick, while the bulbar is very thin and movable, easily sliding back and forth over the front of the eyeball it covers. Because the bulbar is clear, it is easy to see underlying blood vessels. Within the bulbar, conjunctivae are "goblet cells" that secrete an important component of the pre-corneal tear layer, which protects and nourishes the cornea. The fornix is a loose pocket of conjunctiva between the upper eyelid and the eyeball that permits the eyeball to rotate freely.

What is the function of the conjunctiva?

The conjunctiva produces mucous, a clear viscous fluid that lubricates the eyeball, as well as produces some tears, which helps keep the eye clean. However, most tears are produced by the lacrimal glands, which are located at the upper outer corners of each orbit, and spread a smooth layer of mucous and tears over the eye every time you blink. After you blink, the fluid spreads evenly over the eye and then flows into tiny canals in the lids that lead to the lacrimal sac, a pouch at the lower inner corner of each orbit. The mucous and tears from the lacrimal glands and the conjunctiva eventually drain through a passage into the nose.

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