Anatomy of the Eye
Adnexa
A structural anomaly of the adjacent structures of the eye, defined as the lacrimal apparatus, the extraocular muscles and the eyelids, eyelashes, eyebrows and the conjunctiva
Cones
Color perception is the role of _____ There are 6 million to 7 million cones in the average human retina. They are mostly concentrated in the center of the retina, around the fovea. There are three types of ______ cells and each type has a different sensitivity to light wavelengths. One perceives red (about 64 percent), another perceives green (32 percent) and the third perceives blue light (2 percent). Light enters your eye and stimulates the ____ cells when you look at an object. Your brain interprets the signals from the _____ cells to help you determine the color of the object. The red, green and blue _____ work together to create the color spectrum. For example, when the red and blue ______ are stimulated in a certain way, you will see purple. People with normal color vision have all three types of _____ cells working correctly. On the other hand, color blindness occurs when one or more of the ____ types are faulty. For example, if the green ______ is faulty you won't be able to see colors containing blue clearly.
Fovea
In the eye, a tiny pit located in the macula of the retina that provides the clearest vision of all. Only in the _____ are the layers of the retina spread aside to let light fall directly on the cones, the cells that give the sharpest image. Also called the central _____ or ____ centralis. The ______ is responsible for sharp central vision (also called foveal vision), which is necessary in humans for activities for which visual detail is of primary importance, such as reading and driving.
Physiology
Light entering the eye passes through the cornea, then through the pupil, and on through the crystalline lens and the vitreous to the retina. The cornea, aqueous humor, lens, and vitreous are the refracting media of the eye. Changes in the curvature of the lens are brought about by its elasticity and by contraction of the ciliary muscle. These changes focus light rays on the retina, thereby stimulating the rods and cones. The rods detect light, and the cones detect colors in the visible spectrum. The visual area of the cerebral cortex, located in the occipital lobe, registers them as visual sensations. The amount of light entering the eye is regulated by the iris; its constrictor and dilator muscles change the size of the pupil in response to varying amounts of light. The eye can distinguish nearly 8 million differences in color. As the eye ages, objects appear greener. The principal aspects of vision are color sense, light sense, movement, and form sense.
Describe the structure and definition of the orbit?
Pear shaped bony cavity in the skull, made up of 7 bones, house the globe, extraocular muscles, blood vessels, nerves, all cushioned by layers of fat.
Orbit
Pear shaped bony cavity in the skull, made up of 7 bones, house the globe, extraocular muscles, blood vessels, nerves, all cushioned by layers of fat.
What are 4 reasons why tears are important to the function of the eye?
Tears keep your eyes wet and smooth, and help focus light so you can see clearly. They also protect your eyes from infections and irritating things, like dirt and dust.
Macula
The _____ is part of the retina at the back of the eye. It is only about 5mm across but is responsible for our central vision, most of our colour vision and the fine detail of what we see. The ______ has a very high concentration of photoreceptor cells - the cells that detect light. They send signals to the brain, which interprets them as images. The rest of the retina processes our peripheral, or side vision.
Sclera
The ______, or white of the eye, is a protective covering that wraps over most of the eyeball. It extends from the cornea in the front to the optic nerve in the back. This strong layer of tissue, which is no more than a millimeter thick, gives your eyeball its white color. It also protects and supports your eye. The _____ functions as the supporting wall of the eyeball. It helps maintain your eyeball's shape, and protects it from injury.
Retina
The _______ is a thin layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. The purpose of the _____ is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. The ______ processes light through a layer of photoreceptor cells. These are essentially light-sensitive cells, responsible for detecting qualities such as color and light-intensity. The ______ processes the information gathered by the photoreceptor cells and sends this information to the brain via the optic nerve. Basically, the _______ processes a picture from the focused light, and the brain is left to decide what the picture is.
Vitreous Humor
The ________ ______ comprises a large portion of the eyeball. It is a clear gel-like substance that occupies the space behind the lens and in front of the retina at the back of the eye. Because the eye must process visual data, this liquid must be clear enough for light to easily pass through it. Most of this humor consists of water, as well as a lower amount of collagen, salt, and sugar. This humor is a stagnant (immobile) fluid that is not served by any blood vessels and is not actively regenerated or replenished. If a substance enters the _______ _______, it will remain suspended in the gel until it can be surgically removed. These substances, which can include blood or clumps of cells, are collectively referred to as floaters. If left alone, floaters can affect a person's field of vision. As people age, vitreous thins. Problems with the ______ ________ may ultimately lead to detachment of the retina from the back wall of the eye, which may require surgery.
Anterior Chamber
The ________ _______ is the front part of the eye between the cornea and the iris. The _______ _______ is filled with aqueous humor, which is a watery fluid that provides nourishment to the interior eye structures and helps to keep the eyeball inflated. The aqueous humor flows in and out.
Conjunctiva
The ____________ is the clear tissue that covers the white part of the eye and the inside of the eyelids. A healthy __________ is necessary for the eye to function normally, as it helps to create a suitable environment for the cornea, which is responsible for focusing most of the light that enters the eye. It helps protect the eye by keeping out foreign objects and microorganisms. It also helps maintain the tear film.
What is the principal function of the cornea?
The cornea's main function is to refract, or bend, light. The cornea is responsible for focusing most of the light that enters the eye.
What are the 4 primary structures included in the adnexa?
The eyebrows, eyelids, eyelashes, lacrimal gland and drainage apparatus
What are the 3 functions of the eyelid?
The eyelid provides protection to the cornea, disperses the tear film across the ocular surface, removes debris, and plays an important role in producing the tear film.
What are the 3 functions of the eyelid?
The eyelid provides protection to the cornea, disperses the tear film across the ocular surface, removes debris, and plays an important role in producing the tear film. - The eyelid provides protection to the cornea, disperses the tear film across the ocular surface, removes debris, and plays an important role in producing the tear film. The function of the lacrimal apparatus is to produce tears, channel them to the surface of the eye where they maintain moisture, and flush debris and waste material from the ocular surface.
Pupil
The opening within the iris through which light passes before reaching the lens and being focused onto the retina. The size of the opening is governed by the muscles of the iris, which rapidly constrict the ______ when exposed to bright light and expand (dilate) the ______ in dim light.
Iris
The part of the eye that determines its color, the ____ is the muscular curtain that sits near the front between the cornea on the outside and the lens. The _______ consists of two sheets of smooth muscle with contrary actions: dilation (expansion) and contraction (constriction). These muscles control the size of the pupil and thus determine how much light reaches the retina.
Rods
The retina of the eye has two types of light-sensitive cells called ______ and cones, both found in the layer at the back of your eye which processes images. ____ are rod like structures located through the retina except for the fovea, and are required for dim light (twilight/night) vision. Both these visual components contain light sensitive pigments. The most basic and crucial function of photoreceptors is to perceive light, which is the function of _____. _____ are located throughout the retina except signals to determine light and shadow. On average, there are 120 million _____ in the human eye, which are more than a thousand times as sensitive as individual cones. _____ pick up signals from all directions, improving our peripheral vision, motion sensing and depth perception. However, ____ do not perceive color: they are only responsible for light and dark.
Cornea
The transparent part of the eye that covers the iris and the pupil and allows light to enter the inside. Important functions of ______ in the eye include protecting the structures inside the eye, contributing to the refractive power of the eye, and focusing light rays on the retina with minimum scatter and optical degradation. The _______ tends to repair itself quickly from minor abrasions. However, deeper abrasions may cause scars to form on the_______, which causes the _______ to lose its transparency, leading to visual impairment.
Optic Nerve
They play a crucial role in your ability to see. The _______ ______ is composed of millions of nerve fibers. It's an extension of your central nervous system, which includes your brain and spine. The _____ ______ transmits electrical impulses from your eyes to your brain. Your brain processes this sensory information so that you can see.
-How does the eye convert light rays to a perceived image?
When light hits the retina (a light-sensitive layer of tissue at the back of the eye), special cells called photoreceptors turn the light into electrical signals. These electrical signals travel from the retina through the optic nerve to the brain. Then the brain turns the signals into the images you see.
Aqueous Humor
__________ ________ is a thin, watery fluid located in the anterior and posterior chambers of the eye. In addition to supporting the shape of this area, aqueous supplies nutrients and nourishment to parts of the eye that lacks blood supply. It also removes waste. Improper drainage of the ______ _______ can cause an increase in intraocular pressure (pressure inside the eye (IOP)). This increase can result in loss of vision or contribute to the development of glaucoma. Issues with ________ ________ drainage can be treated surgically.
Eyelids
a movable fold of skin and muscle that can be closed over the eyeball or opened at will. Helps protect the eye from injury, controls light exposure to the eye, and aids in the lubrication of the ocular surface.
Eyelashes
can be defined as the short strands of hair that grow at the edges of the eyelids. Are a first line of defense for your eyes, keeping airborne dirt, dust, lint and other debris from reaching the delicate eye tissues. With eyes open, eyelashes catch some airborne debris, but when closed, eyelashes form a nearly impenetrable barrier against foreign irritants in the eye.
Ciliary Body
is found behind the iris and includes the ring-shaped muscle that changes the shape of the lens when the eye focuses. It also makes the clear fluid that fills the space between the cornea and the iris
Tear Duct
is part of the tear drainage system. It drains tears through the nasal bone and into the back of the nose. _____ _____ are an important component of eye health. The tear-producing glands in your eyes make different types of tears to satisfy different needs. Other types of tears lubricate the eye or wash away Irritants.
