The organs by which we can see anything are the two eyes. The ray of lights comes from any object and falls in the eyes and we can see the object. But the process is not so easy. Now we shall try to understand about the different parts of the eye.
The Eyelids and Conjunctiva:
The part of the eye seen on the face consists of the part that is white, and a circular area in front that looks dark. The white part of the eye is formed by outermost coat of the eyeball which is called the sclera. A thin transparent membrane namely the ocular conjunctiva, by which the sclera is lined by. The circular dark part in the centre of the eye is the iris which we see through a transparent disk like structure or the cornea which covers it. At the centre of the iris there is an aperture called the pupil. The pupil of the both eyes appears black because the interior of the eye is dark. When we viewed the eyes we see only a small part of the eyeball in the interval between the upper and lower eyelids which is called the palpebral fissure .
The eyelids, both upper and lower protect the eyeball from injury. They provide protection against mechanical injury by the reflex closure at the moment any object suddenly approaches the eyes. They also help to keep the cornea moist as when the eyelids of the eyes are closed, a capillary space separates the posterior surface of the lids from the cornea and the sclera’s anterior part , which is called the conjunctival sac, containing a thin film of lacrimal fluid.
When the eyes remain open the cornea has a tendency to dry up, by periodic, unconscious closure of the eye lids prevent it. at the timer of happening this the film of lacrimal fluid over the cornea is replenished. Moreover, the eye lids protect the eyes from sudden exposure to bright light by reflux closure.
So, we have seen above that the space separating the upper and lower eye lids is called the palpebral fissure. The medial and lateral ends of the fissure are called angles of the eyes. Each angle is named the canthus. The lateral canthus is in contact with the sclera and at the medial canthus the lower and upper lids are separated by a triangular interval called the lacus lacrimalis. There is a rounded pink elevation at the floor of this area is called the llacrimal caruncle.Each eyelids of the eyes has a free edge to which eyelashes are attached with. A slight elevation called the lacrimal papilla situated just lateral to the lacrimal caruncle at each lid margin. There has a small aperture called the lacrimal punctumon the meeting of the papilla. It to be noted that the punctum of the eyes is normally in direct contact with the ocular conjunctiva.
The skeleton of each eyelid is formed by a mass of fibrous tissue called the tarsal plate or the tarsus.
Now we have to discuss about the Lacrimal Apparatus and the Lacrimal Sac of the Eyes. Go to the next Page.