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Structure
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Miscellaneous
100
They move the eye in the socket
What are muscles?
100
It is tough, clear covering over the iris and the pupil that helps protect the eye. Due to its shape, the it does ⅔ of the refracting (i.e. focusing) of the light that comes into the eye. It begins the process of bending light to make an image on the retina; the lens finishes the job.
What is the cornea?
100
The layer of pink, light-sensitive tissue located at the back of the eye. The cornea and lens work together to focus light and images this, which stimulate a series of chemical and electrical events within tissue. These signals are then sent from to the brain via the optic nerve. If one were to think of the eye as a type of complex camera, it would be equivalent to the film inside of the camera. It is also like a movie screen in that it is where images are projected. It is made of brain tissue and is considered part of the central nervous system.
What is retina?
100
The colorful, shiny, iridescent material located behind the retina. It reflects light back through the retina, which increases the light available to the retina’s photoreceptors. This improves vision in low-light situations, but the perceived image may be blurry, due to interference from the reflected light. When light shines into the eye of an animal, the animal’s pupils appear to glow. Many of the animals who have these are either nocturnal (e.g. owls), are night-hunters (e.g. lions), are awake most of the night (e.g. cows and sheep), or are deep sea animals (e.g. sharks and skates). Most diurnal animals (e.g. most primates, squirrels, some birds, red kangaroos, pigs, and humans) do not have them.
What is the tapetum lucidum?
100
It is a break in visual field that is caused by the optic disk, which is an area on the retina where there are no light-sensitive cells. It is not normally perceived, because the brain fills in missing details based on surrounding images and information from the other eye.
What is the blind spot?
200
It is a jelly like substance that gives the eye it's shape.
What is Vitreous Humor?
200
It is clear, flexible, crystalline structure that focuses light and images on the eye’s retina. It is flexible and can change shape - ciliary muscles surrounding it push and pull on it so that the eye is able to shift its focus between objects that are close up and objects that are far away.
What is the lens?
200
One kind of light-sensitive cell within the retina. They are responsible for color vision. There come in 3 types: one that absorb long-wavelength light (allowing for the perception of the color red), one that absorb middle-wavelength light (allowing for the perception of green), and one that absorb short-wavelength light (allowing for the perception of blue). Humans are generally trichromatic, meaning that all three types of cones are usually present in the human retina. The brain processes the combinations of these three values which allows the average human to perceive about 1 million different colors. Cows and most other non-primate land mammals are dichromatic (the red ones are not present) and they can only perceive about 10,000 colors.
What are Cone Cells?
200
A brown-black pigment that is found in many parts of the human body. It is highly concentrated in the iris in order to protect the light sensitive nerves in the eye from UV-radiation. All cows have brown eyes. In humans, however, the color of the iris varies depending on the concentration in the iris and the structure of the iris. These two factors work together to cause a variation in eye color.
What is melanin?
200
its is a sphincter muscle that controls how much light enters the eye. It is suspended between the cornea and the lens. In humans it functions to adjust the size of the pupil according to the amount of available light (i.e. it constricts the pupil in bright light and dilates the pupil in dim light). Its color is determined by both the amount of melanin that coats it and the arrangement of proteins within the eye.
What is the iris?
300
The thick, tough, white outer covering of the eyeball that is made up of collagen and elastic fiber. It is also known as the “white of the eye.”
What is the sclera?
300
This is the term used in which both eyes are used separately. By using the eyes in this way, as opposed by binocular vision, the field of view is increased, while depth perception is limited.
What is monocular vision?
300
One kind of light-sensitive cell in the retina. They are more sensitive than cone cells and require less light to function. They almost entirely responsible for night vision. Unlike cone cells, they have little, if any, role in colored vision. There are approximately 125 million in the human retina.
What rod cells?
300
The bundle of nerve fibers that transmits visual information from the retina to the brain.In human it contains between 770,000 and 1.7 million nerve fibers. The fibers of the mammalian central nervous system are incapable of regeneration and, thus damage can cause severe loss of vision or irreversible blindness.
What is optic nerve?
300
This occurs in photos because light from the flash bounces off the back of the eye. The choroid is located behind the retina and is rich in blood vessels, which make it appear red on film
What is red eye?
400
A transparent fluid located in the space between the lens and the cornea. Maintains the fluid pressure within the eye. and provides nutrition (e.g. amino acids and glucose) to the inside surface of the cornea and the lens. Increased production or decreased outflow may lead to glaucoma, an increased pressure within the eye.
What is the Acqueous Humor?
400
vision using two eyes with overlapping fields of view, allowing good perception of depth.
What is binocular vision?
400
It is the hole in the center of the iris that allows light into the inner eye. Light enters the eye through the and the iris regulates the amount of light. In humans it is round, but horizontal and vertical slits are present in other species (horizontal slit , such as those found in cows’ eyes, are effective in the vertical plane and allow for better detection of predators as they move rapidly into the field of vision). It appears black because light rays are absorbed by the tissues within the eye. Think of a hole in the ground. It’s dark in there.
What is the pupil?
400
Condition in which the retina peels away from its underlying layer of support tissue. Can be corrected with medical treatment.
What is detached retina?
400
The fatty layer that surrounds each nerve fiber. The main function of the is to increase the speed at which nerve impulses travel along the fiber.
What is myelin sheath?
500
It is the mucous membrane that covers the front of the eye and lines the inside of the eyelids.
What is the conjunctiva?
500
Irregular curvature of the lens or cornea that causes a blurring.
What is astigmatism?
500
It is a small, central pit composed of closely packed cones in the eye. It is located in the center of the macula lutea of the retina. it is responsible for sharp central vision, which is necessary in humans for activities where visual detail is of primary importance, such as reading and driving.
What is the fovea?
500
It is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. It provides oxygen and nourishment to the outer layers of the retina.
What is the choroid?
500
A group of eye conditions that lead to damage of the optic nerve. In most cases, damage to the optic nerve is due to increased pressure within the eye.
What is glaucoma?