Silmänpallo

Silmänpallo, scientifically known as the eyeball, is the organ of sight. It is a roughly spherical structure located within the eye socket of the skull. Its primary function is to detect light and convert it into electrochemical impulses that are then transmitted to the brain via the optic nerve, where they are interpreted as vision.

The outer layer of the eyeball consists of the sclera, the tough, white protective layer, and the cornea, the transparent front part that covers the iris and pupil. Beneath the sclera is the uvea, which comprises the choroid, ciliary body, and iris. The choroid is a vascular layer that nourishes the retina. The ciliary body controls the shape of the lens for focusing, and the iris is the colored part of the eye that regulates the size of the pupil, controlling the amount of light entering the eye.

The innermost layer is the retina, a light-sensitive tissue containing photoreceptor cells called rods and cones. Rods are responsible for vision in low light conditions, while cones detect color and detail in brighter light. Light entering the eye is focused by the cornea and the lens onto the retina. From the retina, nerve impulses are sent through the optic nerve to the brain's visual cortex for processing. The space within the eyeball is filled with fluids: the aqueous humor in the front chamber and the vitreous humor in the larger posterior chamber, both of which help maintain the eyeball's shape and refract light.