The optic nerve

 

 

Most nerves contain fibers, some of which transmit sensory information to the central nervous system, while others - commands from the brain to activate the muscles and glands. The optic nerves are narrowly specialized and designed to transmit sensory information to the visual centers of the brain. They are stretched straight out of the eye into the brain.

 

Conjunctiva- the shell covering the eyeball in front and under the eyelids. It is equipped with a dense network of blood vessels and is very sensitive.

 

Cornea- the main lens of the eye, which forms its outer transparent layer, covering the color iris and pupil, or the central opening through which the light passes, with Iris - the colored diaphragm, the central opening surrounding the pupil through which light enters the eye. Circular muscle fibers cause the iris to contract, thereby narrowing the pupil; radial fibers, on the other hand, expand the iris and pupil, d The crystalline lens is an internal lens that adjusts the focus. The lens is transparent, with a biconvex surface that refracts the rays of light falling on it, so that they diverge or converge on the retina.The lens is contained in the fibrous capsule, and the supporting ligaments hold the lens in place.

 

The ciliary body on each side of the lens has a "focusing muscle" - muscle fibers that contract or relax, changing the shape of the lens and thereby focusing the vision on distant or near objects, g The anterior chamber between the lens and the cornea is filled with a transparent liquid called watery moisture, h Sclera is a dense white tissue that is visible around the iris, but covers the eyeball completely, except for the entrance of the optic nerve from behind, i Vascular membrane - a layer of tissue located immediately under the net mended and colored in brown or black, since extremely densely packed blood vessels supplying the retina, j Retina - shell of light-sensitive cells, called photoreceptors, which lines the back of the eyeball. The rays of light, focused on it by lenses, are transformed into nerve impulses, to the Yellow spot - a small depression in the retina on the visual axis of the eyeball, where vision is the best. It contains only the color receptors, the so-called conical cells.

 

The optic nerve- a bundle of nerve fibers stretched from the optic disc on the retina to the brain. The nerves from the left sides of both retinas are connected to one half of the brain, and the nerves from the right sides to the other half. Two visual centers receive a mixed picture from both eyes in a ratio of 50 to 50. m Vitreous humor is a transparent jelly that fills the inside of the eye behind the lens and ensures its shape is preserved. It contains the smallest specks that can be seen, staring fixedly on a white surface. They are called "quicksand".

 

The optic disc is the beginning of the optic nerve, the place where it enters the eyeball. It does not contain photosensitive cells and thus forms a blind spot. It is sometimes noticeable as a black spot on the periphery of the visual field.