Do our eyeballs have skin?

Question

I know this is a really stupid and random question, but I was wondering that today. Do our eyeballs have skin? Does anyone mind telling me what eyeballs are made out of?

Thanks!!!

Answer 1

Our eyes are made from cells and protein. Its is VERY complex, in fact the only other animal that has eyes like ours are octopuses.

Answer 2

The outer layer, or skin if you prefer, is called the sclera.

Answer 3

No, they don't have skin.  I'm not exactly sure what they're made of though.  Something squishy.  

Answer 4

No, there is no "skin" on our eyeballs - but there is a layer called the Conjunctiva (which also covers the inside of our eyelids).

Our eyeballs have an opaque outer layer called the "sclera", which covers them everywhere except the cornea (the transparent bit at the front). The sclera is also what the muscles which move the eyeball are attached to. The cornea is differently-constructed in order to permit light to pass through it into the eye (it has ver few cells in it, making it very transparent). The cornea has a different refractive index from the air, and it therefore refracts (bends) and focusses light entering the eye, giving a sharp image.

Just inside the cornea is a muscular tissue called the iris (named after the Greek goddess of the rainbow) which has a hole (the pupil) in its centre, and which can change in diameter to allow more or less light into the eye, depending on light intensity (preventing light-damage to the sensitive tissues in the eye).

Inside the eye, there are two chambers - the frontmost is the "anterior chamber", or the "aqueous chamber" - and it is filled with the "aqueous humour", which is produced from the blood, and is very similar in composition to the blood plasma (the liquid, non-cellular component of blood).

Dividing the anterior chamber from the posterior chamber is the lens and the ciliary muscles attached to it. The lens is packed with special proteins called crystallins, and as a result has a different refractive index from the aqueous humour, and it performs the fine-focussing of light entering the eye. It is flexible, and contracting the ciliary muscles actually changes its shape, and changes the angles at which the light is bent - allowing fine-focussing on objects at different differences. As you age, your lens stiffens, and you become less able to focus - requiring reading-glasses.

Behind the lens is the posterior chamber - or "vitreous chamber". This is the larger of the two chambers, comprising most of the eye's volume. It is filled with the jelly-like "vitreous humour", which acts as a shock absorber, preventing impact from damaging the eye. It also acts as a spacer, allowing enough distance between the focussing tissues at the front (the cornea and lens) to actually get a nice, sharp image resolved on the rear of the eye.

The rear of the eye is where the light is actually detected, by a special, photosensitive tissue called the retina. The retina is composed of two cell types - rods and cones. Rods just detect ALL incoming light, and they work well under low light conditions. There are three different cones - red, blue, and green - and they each detect a different wavelength (colour) of light, and therefore allow the perception of colour. Cones do not work well in dim light, however (they need more light to actually work with) - so at night, you can usually only see in monochrome.

There are other cell types in the retina - like supporting cells which nurture the rods and cones, and the nerves which transmit the signals from the rods and cones to the brain via the optic nerve. Interestingly, our retina is actually constructed "backwards": the nerves are in front of the rods and cones (ie - "in the way" of the light), and therefore the nerves must pass *through* the layer of photoreceptor cells to head to the brain; the area where they pass through therefore has no photoreceptor cells (it is our "blind spot", and the image there is filled-in by the brain afterwards).

Answer 5

They don't have skin as such, but our corneas have a thin protective layer called the conjunctiva.

Our eyes are primarily made from proteins. That's why they are so delicate.