The conjunctiva covers the sclera

Sclera

The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest...

 (white part of the eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

) and lines the inside of the eyelid

Eyelid

An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...

s. It is composed of rare stratified columnar epithelium.

Function

The conjunctiva helps lubricate the eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

 by producing mucus

Mucus

In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

 and tears

Tears

Tears are secretions that clean and lubricate the eyes. Lacrimation or lachrymation is the production or shedding of tears....

, although a smaller volume of tears

Tears

Tears are secretions that clean and lubricate the eyes. Lacrimation or lachrymation is the production or shedding of tears....

 than the lacrimal gland

Lacrimal gland

The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called...

.
It also contributes to immune surveillance

Immune system

An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

 and helps to prevent the entrance of microbes into the eye.

Gross anatomy

The conjunctiva is typically divided into three parts:

Part	Area
Palpebral or tarsal conjunctiva	lines the eyelids
Bulbar or ocular conjunctiva	covers the eyeball, over the sclera Sclera The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest... . This region of the conjunctiva is tightly bound to the underlying sclera by Tenon's capsule and moves with the eyeball movements.
Fornix conjunctiva	Forms the junction between the bulbar and palpebral conjunctivas. It is loose and flexible, allowing the free movement of the lids and eyeball. .

Diseases and disorders

Disorders of the conjunctiva and cornea

Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

 are a common source of eye complaints.

The surface of the eye is exposed to various external influences and is especially susceptible to trauma

Physical trauma

Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...

, infections, chemical irritation, allergic reactions and dryness

Keratoconjunctivitis sicca

Keratoconjunctivitis sicca , also called keratitis sicca, xerophthalmia or dry eye syndrome is an eye disease caused by eye dryness, which, in turn, is caused by either decreased tear production or increased tear film evaporation. It is found in humans and some animals...

.

The conjunctiva can become inflamed

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

 secondary to bacterial infection. The resultant condition is known as conjunctivitis

Conjunctivitis

Conjunctivitis refers to inflammation of the conjunctiva...

 and commonly referred to as pinkeye.

Conjunctival irritation can occur for a wide variety of reasons including dry eye and overexposure to VOCs (Volatile organic compound

Volatile organic compound

Volatile organic compounds are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and...

s).

With age, the conjunctiva can stretch and loosen from the underlying sclera, leading to the formation of conjunctival folds, a condition known as conjunctivochalasis

Conjunctivochalasis

Conjunctivochalasis is a common eye surface condition characterized by the presence of excess folds of the conjunctiva located between the globe of the eye and the eye-lid margin.-Symptoms and Diagnosis:...

.

See also

• Pinguecula
  Pinguecula
  A pinguecula is a common type of conjunctival degeneration in the eye.-Presentation:It is seen as a yellow- white deposit on the conjunctiva adjacent to the limbus . It is to be distinguished clinically from pterygium, which is a wedge shaped area of fibrosis that appears to grow into the cornea....
  
  
• Pterygium
  Pterygium
  Pterygium most often refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera. It is usually present in the palpebral fissure. It is associated with, and thought to be caused by ultraviolet-light exposure , low humidity, and dust...
  
  
• Rougine
  Rougine
  A rougine is an instrument used in Ophthalmology. It is used to operate on the conjunctival sac....
  
  
• Subconjunctival hemorrhage
  Subconjunctival hemorrhage
  thumb|right|250px| A stress induced subconjunctival hemorrhage in the left eye one week after hemorrhaging. Same hemorrhage four weeks after hemorrhaging. Some of the blood in the [[sclera]] has turned yellow, like a bruise....
  
  
• Conjunctivochalasis
  Conjunctivochalasis
  Conjunctivochalasis is a common eye surface condition characterized by the presence of excess folds of the conjunctiva located between the globe of the eye and the eye-lid margin.-Symptoms and Diagnosis:...
  
  
• Dry eye

External links

• Medicinenet.com (1999). Conjunctiva. Retrieved July 25, 2004.