silmänpallon

Silmänpallo, also known as the eyeball, is the primary organ of vision. It is a roughly spherical structure located within the orbit of the skull, responsible for detecting light and transmitting visual information to the brain. The outer layer of the silmänpallo is the sclera, a tough, white, protective casing. The front part of the sclera is transparent and is called the cornea, which helps to refract light entering the eye.

Beneath the sclera is the uvea, a vascular layer that includes the choroid, iris, and ciliary body. The choroid provides nourishment to the retina. The iris is the colored part of the eye that controls the size of the pupil, regulating the amount of light that enters. The ciliary body contains muscles that change the shape of the lens for focusing.

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 focused by the cornea and lens strikes the retina, where it is converted into electrical signals. These signals are then transmitted through the optic nerve to the brain for interpretation as images.

The interior of the silmänpallo is filled with two types of fluid: the aqueous humor in the front chambers and the vitreous humor filling the large posterior cavity. These fluids maintain the shape of the eyeball and help to refract light. The complex structure and intricate functioning of the silmänpallo enable us to perceive the world visually.