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Equine Special Senses - Horse Anatomy (view source)
Revision as of 16:34, 22 November 2012
, 16:34, 22 November 2012→Adnexa
[[Image:Adnexa.jpg|thumb|right|200px|Adnexa - Copyright David Bainbridge]]
[[Image:Adnexa.jpg|thumb|right|200px|Adnexa - Copyright David Bainbridge]]
The adnexa refers to the accessory structures of the eye, including the eyelids and the lacrimal apparatus. It contains three layers of the tear film:
The adnexa refers to the accessory structures of the eye, including the eyelids and the lacrimal apparatus.
=====Lacrimal Apparatus=====
Function of the cornea depends on the integrity of the lacrimal system, a major component is the '''pre-corneal tear film'''. This is the outer-most layer of the corneal epithelium, it should stay attached to the corneal and conjunctival surface. Pre-corneal tear film functions to:
*Lubricate the cornea and conjunctiva, blinking spreads it over the surface.
*Transfer oxygen and glucose to the avascular cornea
*Provides antibodies/inflammatory cells to the cornea in the event of an irritation or foreign body.
*Flushes away foreign body material.
*Maintains an optically smooth corneal surface so that light can pass freely into the cornea.
The '''pre-corneal tear film''' is made up of three major constituents:
*Lipid outer layer: produced by the '''tarsal aka meibomian glands''' (modified sebaceous glands) in the '''tarsal plate''' of the eyelids. This prevents evaporation of the underlying layers and overflow of tear film onto the eyelids; therefore it stops dehydration of the cornea.
*Aqueous layer: in the middle, performs the primary functions of the tear film. The '''lacrimal gland''', '''superficial gland of the nicitating membrane''' and, '''Hardenian gland''' and '''accessory lacrimal glands''' in the conjunctiva contribute to its formation. Evaluate this layer with the Shirmir Tear Test.
*Mucin: is the inner layer which sticks the aqueous phase to the corneal epithelium. It is produced by conjunctival goblet cells, mainly in the '''conjunctival fornixes'''. Evaluate with fluorescein breakup time.
==Ear==
==Ear==