Vitreous Humor, Sclera and Other Yukky Eye Stuff
Eyes are one of the most complex organs humans have. In fact the optic nerve connection to the brain is so complex and delicate that no one has ever succeeded in transplanting the whole eye (the cornea, the clear covering on the front part of the eye, has been successfully transplanted).
The front of the eye consists of a 'pupil' – an opening in the middle of the eyeball which is surrounded by the 'iris' – the muscle-like part that adjusts the size of the pupil opening depending on the amount of incident light (it also defines the color of the eye), and the white 'sclera' on the periphery. Behind the pupil is the 'lens', which focuses the image of the outside world onto the retina at the back of the eye. Light intensity and the color of the picture is then converted into electric signals and sent to the brain via the optic nerve. The eyeball is filled with a transparent, slimy, gel-like substance called 'vitreous humor'.
Ah, and let's not forget the eye-lids, which blink 10 to 15 times a minute to wash away dust and keep our eyes moist. The blink rate actually depends on our emotional state too. It increases when we like someone, or when we feel uncomfortable, stressed or frightened.
