anatomy of the eye
The eye is distinctive in that it is able to move in numerous directions to maximize the field of vision. See much more eye photos.
The tough, outermost layer of the eye is known as the sclera. It maintains the shape of the eye. The front sixth of this layer is clear and is known as the cornea. All light should initial pass via the cornea when it enters the eye. Attached to the sclera are the muscles that move the eye, known as the extraocular muscles.
anatomy of the eye
The choroid (or uveal tract) is the second layer of the eye. It contains the blood vessels that supply blood to structures of the eye. The front component of the choroid contains two structures:
The ciliary body - The ciliary body is a muscular region that is attached to the lens. It contracts and relaxes to control the size of the lens for focusing.
The iris - The iris is the colored component of the eye. The color of the iris is determined by the color of the connective tissue and pigment cells. Much less pigment makes the eyes blue much more pigment makes the eyes brown. The iris is an adjustable diaphragm about an opening known as the pupil.
The iris has two muscles: The dilator muscle makes the iris smaller and therefore the pupil bigger, permitting much more light into the eye the sphincter muscle makes the iris bigger and the pupil smaller, permitting much less light into the eye. Pupil size can alter from 2 millimeters to 8 millimeters. This indicates that by changing the size of the pupil, the eye can alter the quantity of light that enters it by 30 times.
anatomy of the eye
The innermost layer is the retina -- the light-sensing portion of the eye. It contains rod cells, which are responsible for vision in low light, and cone cells, which are responsible for color vision and detail. In the back of the eye, in the center of the retina, is the macula. In the center of the macula is an region known as the fovea centralis. This region contains only cones and is responsible for seeing fine detail clearly.
The retina contains a chemical known as rhodopsin, or "visual purple." This is the chemical that converts light into electrical impulses that the brain interprets as vision. The retinal nerve fibers collect at the back of the eye and form the optic nerve, which conducts the electrical impulses to the brain. The spot where the optic nerve and blood vessels exit the retina is known as the optic disk. This region is a blind spot on the retina simply because there are no rods or cones at that location. Nevertheless, you are not conscious of this blind spot simply because every eye covers for the blind spot of the other eye.
anatomy of the eye
When a physician looks at the back of your eye via an ophthalmoscope, here's the view:
Inside the eyeball there are two fluid-filled sections separated by the lens. The bigger, back section contains a clear, gel-like material known as vitreous humor. The smaller, front section contains a clear, watery material known as aqueous humor. The aqueous humor is divided into two sections known as the anterior chamber (in front of the iris) and the posterior chamber (behind the iris). The aqueous humor is produced in the ciliary body and is drained via the canal of Schlemm. When this drainage is blocked, a illness known as glaucoma can result.
The lens is a clear, bi-convex structure about 10 mm (.four inches) in diameter. The lens modifications shape simply because it is attached to muscles in the ciliary body. The lens is utilized to fine-tune vision.
Covering the inside surface of the eyelids and sclera is a mucous membrane known as the conjunctiva, which assists to maintain the eye moist. An infection of this region is known as conjunctivitis (also known as pink eye).
The eye is distinctive in that it is able to move in numerous directions to maximize the field of vision, however is protected from injury by a bony cavity known as the orbital cavity. The eye is embedded in fat, which offers some cushioning. The eyelids safeguard the eye by blinking. This also keeps the surface of the eye moist by spreading tears over the eyes. Eyelashes and eyebrows safeguard the eye from particles that might injure it.
anatomy of the eye
Tears are produced in the lacrimal glands, which are situated above the outer segment of every eye. The tears ultimately drain into the inner corner of the eye, into the lacrimal sac, then via the nasal duct and into the nose. That is why your nose runs when you cry.
anatomy of the eye
There are six muscles attached to the sclera that control the movements of the eye.
anatomy of the eye