Parts of the Human Eye

The eye is a wonderful and the most complex organ of the human body. It is strange to learn that such a small organ has so many parts. The following account provides you information on the parts of the human eye and its function along with the particular functions assigned to each part of it.

What are the Parts of the Human Eye and their Functions

The Cornea: The cornea is a round, transparent dome that acts as the outer window of the eye. It is the structure that focuses the light that enters the eye. It comprises five parts. All the parts work together to protect the eye and help in the proper working of the cornea as a whole.

The Lens: The lens is that part of the human eye that is located immediately behind the iris. It is transparent, elastic and crystalline. Its role is to focus the light and move towards the retina.

The Uvea: The uvea forms the center of the eyeball. It is made up of three parts, choroid, ciliary body and iris. The choroid is a thin membrane that is placed between the outer protective sclera and retina. Its function is to prevent the rays of light from bouncing off on the back side of the eye. Malfunctioning of the choroid may cause the formation of confusing images. The role of ciliary body is to assist in the adjustment of the shape of the lens. The iris is described as a separate part in this section of the article.

The Iris: The colored part of the eye is known as iris. It is present in the eye in the form of a thin diaphragm. The iris lies between the cornea and the crystalline lens. The color is due to the presence of a pigment. It is the iris that gives your eyes a particular color. The basic iris colors are blue, green and brown. Majority of humans have varying shades of these colors. It is composed of connective tissues and smooth muscle fibers. The composition of the iris enables it to dilate or contract the pupil, which in turn controls the amount of light that falls on the retina.

The Retina: The retina is the innermost layer of the eye. It consists of nerve tissue that senses the light entering the eye. Its function is to send impulses through the optic nerve back to the brain, where it gets translated into the images that we see. There are four types of light-sensitive receptors present in the retina. These are rods and three different types of cones. Some cones absorb long-wavelength, some absorb middle-wavelength and the rest absorb short-wavelength.

The Pupil: The hole in the center of the eye through which the light passes, is called the pupil. The pupil gets bigger and smaller depending on the amount of light falling on the eye.

The Optic Nerve: The continuation of the axons of the ganglion cells in the retina is known as the optic nerve. It connects the eye with the brain. The optic nerve emerges from the back of the eye, travels through the skull and stops inside the skull bone. From the skull bone, the nerves move through the lateral geniculate body, the internal capsule and ends up at the back of the brain. This part of the brain is known as visual cortex. It is responsible for receiving information from the eyes and interpreting it.

The Sclera: The sclera is the whitish, opaque part of the eye, which is connected to the cornea. Its role is to provide protection and meet the purpose of attachment for the extraocular muscles that enables eye to move.

The Vitreous Humor: It is the jelly like substance that is present within the interior chamber behind the lens. It is that part of the human eye whose role is to provide pressure inside the eye and keep it inflated.

How Does the Eye Work?

The light first enters the eye through the cornea. It bends the rays of light and moves towards the pupil and iris. After passing the pupil and iris, the light rays falls on the lens of your eye. The lens of the eye functions like a camera and brings the light in focus. The lens sends the light to the back of the eye, where it reaches the retina. The photoreceptor nerve cells of the retina transforms the light into electrical impulses. These electrical impulses are then sent to the optic nerve of the eye, which transmits the information to the brain.

Since both the eyes are separated by the nose, they have different fields of vision. Due to the difference in the visual fields, each eye sees at different angles of the object, and so gives different information to the brain. Along the way at the optic chiasma, some of the nerves from each optic nerve cross over so as to separately collect the information from the left and right side of the field of vision. The swapping of information takes place one more time at the cell station. This connection works in accordance with the reflexes of the pupils. The information is now received by the visual cortex, which interprets the image at this point.

Thus, both the eyes work together to provide complete information to the brain and enable you to see what you see. Hope, the description on parts of the human eye given here helps you in understanding how the eye works in humans.