Eye Layers

 

Well, here we are at another Wednesday and this week we looking at the what makes up our eyes, many of us have never really looked at our eyes.

Our eyebrows are thickened ridges of skin covered with short hairs, they come over the bone of the skull above the eye, protecting the eye from dust and such. The stop sweat dripping into the eye, they also protect the eye from some blows to the head.

Then we have our eyelids which we all know are folds of skin that open at the front of the eyeball. However, did you know they are made up of four layers an outer layer of skin with hairs we call eyelashes, then there is a layer of muscle, which allow the eyelid to open and close. There is also a layer of fibres and oil glands as well as a thin transparent inner layer.

Our eyelids protect the eye from many things and as soon as something threatens the eye, it will instantly close this is a reflex reaction. Out eyelids also allow us to blink and when we do tears are spread over the eyeball keeping it moist.

Did you know our eyelashes have around 200 fine hairs, with each one lasting about four months before it falls out and is replaced.

The outer layer of the eyeball is made up of the sclera and cornea, the sclera makes up about five-sixths of the layer and the cornea is one-sixth. The sclera is a tough, fibrous membrane and is the part we think of as the white part of the eye. It gives the eyeball its shape and protects the structures inside the eye.  The cornea is transparent and lies in front of the iris and pupil, it makes a small bulge at the front of the eye. It has no blood vessels and it bends the light a little as it enters the eye.

Now to the conjunctiva this is joined continuously with the sclera, it is a thin transparent membrane that forms the inner lining of the eyelids. It also covers the whole surface of the eyeball except for the cornea.  As we need to move the eyeball it is slack around the edges.

Lastly we have the iris and the pupil with the pupil being the small black dot we can see which is actually a hole and around it is a coloured ring called the iris which controls the size of the pupil by opening and shutting.

Next week we will look at eye colour