Term
| Which structure, found along the inner margin of the lid, secretes a lipid-rich product that keeps the eyelids from sticking together? |
|
Definition
| tarsal (Meibomian) glands |
|
|
Term
| The cornea is part of which tunic? |
|
Definition
|
|
Term
| Which color cones are most prevalent in the human eye? |
|
Definition
|
|
Term
| 3 stages of eye development in embryo |
|
Definition
1. optic vesicles
2. lateral bulges form optic cups
3. mesoderm isolates neural tissue from rest of body |
|
|
Term
| In the developing retina, ependymal cells on the outer wall of the optic cup develop into _________. |
|
Definition
|
|
Term
| The site of sharpest vision is the |
|
Definition
|
|
Term
| Where do the photoreceptors of the eye synapse? |
|
Definition
|
|
Term
| What comprises the innermost layer of cells in the retina? |
|
Definition
|
|
Term
| The epithelia covering the inner surface of the eyelids and the anterior surface of the eye are called the palpebral and __________ conjunctivae, respectively. |
|
Definition
|
|
Term
| Circulation of the aqueous humor provides an important route for __________ in addition to forming a fluid _____. |
|
Definition
nutrient and waste transport
cushion |
|
|
Term
| The __________ and transparency of the cornea are vital to eye function as it permits the entry of light into the eye. |
|
Definition
|
|
Term
| In the eye, light from each point of an image is focused on the retina, creating a miniature image of the original that is _________ and __________. |
|
Definition
|
|
Term
| The horizontal and __________ cells of the retina can facilitate or inhibit communication between photoreceptors and ganglion cells. |
|
Definition
|
|
Term
| When light strikes a visual pigment, the retinal molecule changes shape, which changes the __________ of the outer segment. |
|
Definition
|
|
Term
| In the condition called __________, when the ciliary muscle is relaxed and the lens is flattened, the image of a distant object will be focused on the retina's surface. |
|
Definition
|
|
Term
| transparent area on the anterior surface of the eye |
|
Definition
|
|
Term
| Connection between the two eyelids on the lateral end |
|
Definition
|
|
Term
| A mucous membrane covered by a specialized stratified squamous epithelium |
|
Definition
|
|
Term
| Contains glands, which produce the thick secretions that contribute to the gritty deposits that sometimes appear after a good night's sleep |
|
Definition
|
|
Term
| Through its continual blinking, it functions in keeping the surface of the eye lubricated, and it removes dust and debris |
|
Definition
|
|
Term
| The gap that separates the free margins of the upper and lower eyelids |
|
Definition
|
|
Term
| In the developing retina, ependymal cells on the inner wall of the optic cup develop into _________. |
|
Definition
|
|
Term
| Neural tissue of the outer wall of the optic cup forms layers of _____, _____, and _____. |
|
Definition
neurons
ganglion cells
specialized glial cells |
|
|
Term
| The two palpebrae connect medially at the _____. |
|
Definition
|
|
Term
| pocket created where the two conjuctivae become continuous |
|
Definition
|
|
Term
|
Definition
| produces, distributes, and removes tears; the constant tear flow helps keep conjunctival surfaces moist and clean |
|
|
Term
| 6 components of the lacrimal apparatus |
|
Definition
| lacrimal gland, tear ducts, lacrimal puncta, lacrimal canaliculi, lacrimal sac, and the nasolacrimal duct |
|
|
Term
|
Definition
|
|
Term
|
Definition
| slightly alkaline and contain antibacterial enzyme lysozyme and antibodies that attack pathogens before they enter the body |
|
|
Term
|
Definition
| there are 10-12; deliver tears from lacrimal gland to the space behind the upper eyelid |
|
|
Term
|
Definition
| 2 small pores the drain the lacrimal lake |
|
|
Term
|
Definition
| small canals that connect the lacrimal puncta to the lacrimal sac |
|
|
Term
|
Definition
| small chamber within the lacrimal sulcus of the orbit |
|
|
Term
|
Definition
| originates at the inferior tip of the lacrimal sac and passes through the nasolacrimal canal to deliver tears to the nasal cavity |
|
|
Term
| Where does the nasolacrimal duct empty? |
|
Definition
| into the inferior nasal meatus (narrow passageway inferior and lateral to the inferior nasal concha) |
|
|
Term
|
Definition
| conjunctivitis; results from damage to and irritation of the conjunctival surface |
|
|
Term
| The redness of pinkeye is due to what? |
|
Definition
| dilation of blood vessels deep to the conjunctival epithelium; the cornea isn't red because it's avascular |
|
|
Term
| 6 extrinsic muscles of the eye and movements |
|
Definition
| superior rectus (elevates eye), inferior rectus (depresses eye), lateral rectus (moves eye laterally), medial rectus (moves eye medially), superior oblique (moves eye down and laterally), inferior oblique (moves eye up and laterally) |
|
|
Term
|
Definition
| quick, painful, pimple-like infection on the eyelid |
|
|
Term
|
Definition
| blocked gland that is irritated and red but not too painful, and it gets hard from secreted lipid |
|
|
Term
|
Definition
| the three layers of the eye (fibrous, vascular, and neural) |
|
|
Term
|
Definition
| outermost layer consisting of the cornea and sclera |
|
|
Term
| functions of the fibrous tunic |
|
Definition
| provides mechanical support and physical protection; serves as the attachment site for the eye muscles |
|
|
Term
|
Definition
| the border of the continuous sclera and cornea |
|
|
Term
| Which part of the fibrous tunic aids in the focusing process? |
|
Definition
| the curvature of the cornea |
|
|
Term
|
Definition
| aka uvea; contains numerous blood vessels and the intrinsic muscles of the eye |
|
|
Term
| functions of the vascular tunic |
|
Definition
| provides a route for the blood vessels and lymphatics that supply the tissues of the eye, regulates the amount of light that enters the eye, secretes and reabsorbs aqueous humor, and controls the shape of the lens (imp. in focusing) |
|
|
Term
| 3 eye structures in the vascular tunic |
|
Definition
| iris, ciliary body, and choroid |
|
|
Term
|
Definition
| colored part of the eye; visible through the transparent corneal surface; contains blood vessels, pigment cells, and layers of smooth muscle fibers |
|
|
Term
|
Definition
| contraction changes the diameter of the pupil |
|
|
Term
|
Definition
| thickened region that bulges into the interior of the eye that supports the lens and controls its shape |
|
|
Term
| What are the ligaments attached to the ciliary body, and what do they do? |
|
Definition
| suspensory ligaments that extend to the lens to hold it in place posterior to the pupil |
|
|
Term
|
Definition
| vascular layer right inside of the sclera that contains an extensive capillary network that delivers O2 and nutrients to neural tissue in the neural tunic |
|
|
Term
|
Definition
| aka retina; innermost layer of the eye consisting of a thin outer layer and thick inner layer |
|
|
Term
| outer layer of neural tunic |
|
Definition
| pigmented layer that absorbs light |
|
|
Term
| inner layer of neural tunic |
|
Definition
| neural layer, contains the photoreceptors |
|
|
Term
| The interior of the eye is divided into 2 _____ by the _____ and the _____. |
|
Definition
|
|
Term
|
Definition
| smaller, has aqueous humor, and is in front of lens; divided into the anterior chamber (cornea to iris) and posterior chamber (iris to ciliary body and lens) |
|
|
Term
|
Definition
| large, behind the lens; most of the volume is taken up by the vitreous body or humor |
|
|
Term
| eye color is determined by |
|
Definition
| genes that influence density and distribution of melanocytes; density of pigmented epithelium (if light can pass through, eye appears blue) |
|
|
Term
| If there are an increased number of melanocytes on the iris, the eye appears _____. |
|
Definition
| darker- green, brown, and black have increasing numbers |
|
|
Term
|
Definition
| body has highly vascular, pigmented, loose connective tissue; anterior surface has no epithelial covering; posterior surface covered by pigmented epithelium that's part of the neural tunic |
|
|
Term
| The anterior surface of the iris is covered by what? |
|
Definition
| an incomplete layer of fibroblasts and melanocytes |
|
|
Term
| What is the bulk of the ciliary body made of? |
|
Definition
| ciliary muscle- smooth muscular ring that projects into the interior surface of the eye |
|
|
Term
|
Definition
| folds of epithelium covering the ciliary muscle |
|
|
Term
|
Definition
| jagged anterior edge of the thick inner portion of the neural tunic, part of the pigmented layer |
|
|
Term
| Which layer of the eye continues anteriorly across the posterior surface of the iris? |
|
Definition
| pigmented outer layer of the neural tunic |
|
|
Term
| aqueous humor circulation |
|
Definition
| ciliary body to posterior chamber through pupil to anterior chamber to canal of Schlemm to collecting channels and then delivered to veins of sclera |
|
|
Term
| The fluid pressure of which humor retains the eye's shape? |
|
Definition
|
|
Term
|
Definition
| procedure that measures the eye's intraocular pressure within the anterior chamber |
|
|
Term
| normal intraocular pressure |
|
Definition
|
|
Term
| How and at what rate does aqueous humor form? |
|
Definition
| through active secretion by epithelial cells of ciliary body's cell processes at the rate of 1-2 microliters/min. |
|
|
Term
| What does the aqueous humor resemble? |
|
Definition
|
|
Term
| The canal of Schlemm is also called what? |
|
Definition
|
|
Term
|
Definition
| passageway extending completely around the eye at the level of the corneal limbus |
|
|
Term
|
Definition
| when aqueous humor isn't adequately reabsorbed, internal pressure builds, and the retina is eventually damaged, sometimes to the point of blindness |
|
|
Term
| Which structure permits the entry of light into the eye? |
|
Definition
|
|
Term
| The lens has a _____ layer of cells surrounded by _____. |
|
Definition
concentric
dense fibrous capsule |
|
|
Term
| The cells of the lens are _______. |
|
Definition
| slender, elongate, and filled with crystallines |
|
|
Term
|
Definition
| transparent proteins of the lens responsible for both clarity and focusing power of the lens |
|
|
Term
| What is the primary function of the lens, and how is this accomplished? |
|
Definition
| to focus the visual image on the photoreceptors by changing its shape |
|
|
Term
| The tension in the suspensory ligaments resists the tendency of the lens to do what? |
|
Definition
|
|
Term
| The retina contains what types of cells? |
|
Definition
| photoreceptors, pigment cells, supporting cells, and neurons |
|
|
Term
| Where are the blood vessels that provide nutrients to all structures within the eye located? |
|
Definition
|
|
Term
| What is the sclera made up of? |
|
Definition
| dense fibrous connective tissue containing collagen and elastic fibers |
|
|
Term
| Where is the sclera thickest and thinnest? |
|
Definition
| thickest over posterior surface of the eye, near the exit of the optic nerve; thinnest over the anterior surface |
|
|
Term
| What is the function of the sclera? |
|
Definition
| stabilizes the shape of the eye during eye movements |
|
|
Term
| Where do the extrinsic muscles of the eye insert? |
|
Definition
| On the sclera, blending their collagen fibers together |
|
|
Term
| What control the amount of light entering the eye and passing through the lens? |
|
Definition
| the 2 layers of the iris' pupillary muscles |
|
|
Term
| The intrinsic eye muscles are controlled by which part of the nervous system? |
|
Definition
|
|
Term
| The pupils _____ during parasympathetic activation and _____ during sympathetic activation. |
|
Definition
|
|
Term
| pupillary dilator muscles |
|
Definition
| activate in dim light; extend radially away from the edge of the pupil |
|
|
Term
| pupillary constrictor muscles |
|
Definition
| activate in bright light; form concentric circles around pupils |
|
|
Term
| Where is the highest concentration of photoreceptors? |
|
Definition
| on the fovea (site of sharpest vision, where an image falls when we are looking directly at it) |
|
|
Term
|
Definition
| When it passes between mediums of different densities |
|
|
Term
| When does the greatest amount of refraction occur, and what is this called? |
|
Definition
| when light passes from air to the corneal tissues (density like water); static refraction |
|
|
Term
|
Definition
| more refraction that occurs at the lens when light has passed from the aqueous humor (b/c lens is relatively dense) |
|
|
Term
|
Definition
| distance between the center of the lens and an objects focal point (specific point of intersection on the retina), determined by the distance from and object to the lens and the shape of the lens |
|
|
Term
| A closer light source = _____ focal distance. |
|
Definition
|
|
Term
| A rounder lens = _____ focal distance. |
|
Definition
|
|
Term
|
Definition
| images are focused on the retina by the changing shape of the lens to keep the focal distance constant |
|
|
Term
| For close vision, the ciliary muscle is _____, and the lens is _____. |
|
Definition
|
|
Term
| When the ciliary muscle contracts, the ciliary body does what? |
|
Definition
| moves toward the lens the reduce the tension in the suspensory ligaments |
|
|
Term
| What does the lens do for close vision? |
|
Definition
| its elastic capsule pulls it into a more spherical shape, which increases its refractive power, which gives it the ability to focus light from nearby objects onto the retina |
|
|
Term
| For distance vision, the ciliary muscle is _____, and the lens is _____. |
|
Definition
|
|
Term
| When the ciliary muscle is relaxed, the ciliary body does what? |
|
Definition
| pulls the suspensory ligaments at the circumference of the lens, which flattens it |
|
|
Term
| Is the greatest amount of refraction required near or far objects? |
|
Definition
|
|
Term
|
Definition
| the inner limit clear vision that is determined by the degree of elasticity in the lens; increases in distance with age (7-9 cm for children, 15-20 cm for young adults, 83 cm for 60 yr olds) |
|
|
Term
| retinal pigmented epithelia |
|
Definition
| pigmented part of the retina that absorbs light that passes through the neural part, preventing light from bouncing back and producing visual echoes |
|
|
Term
| The RPE also has important _____ with the retina's light receptors that are located in the neural part. |
|
Definition
|
|
Term
| The neural part of the retina contains what types of cells that do what? |
|
Definition
| photoreceptors, supporting cells, and neurons that perform preliminary processing and integration of visual info |
|
|
Term
| Which part of the retina (specifically) contains the photoreceptors? |
|
Definition
| the outermost layer of the neural part, closest to the pigmented part |
|
|
Term
|
Definition
| form the innermost layer of cells in the neural part of the retina; receive visual info from bipolar cells and amacrine cells and transmit it to the brain |
|
|
Term
| Ganglion axons converge at the _____ to form the _____. |
|
Definition
optic disc
optic nerve (CNII) |
|
|
Term
|
Definition
| the optic disc has no photoreceptors, so an image falling here can't be detected |
|
|
Term
|
Definition
| photoreceptors that don't discriminate among colors of light (monochromatic) and are highly sensitive, so they see in dim light |
|
|
Term
|
Definition
| photoreceptors for color vision that give us sharper, clearer images than rods do, but they require more intense light |
|
|
Term
| Photoreceptors synapse with _____ on _____. |
|
Definition
neurons called bipolar cells
ganglion cells |
|
|
Term
| What do horizontal and amacrine cells do? |
|
Definition
| facilitate or inhibit communication between photoreceptors and ganglion cells, leading to altered sensitivity of the retina; play important role in eye's adjustment to dim or brightly lit environments |
|
|
Term
| Where are horizontal cells located? |
|
Definition
| a network of them extends across the outer portion of the retina at the level of the synapses between photoreceptors and bipolar cells |
|
|
Term
| Where are amacrine cells located? |
|
Definition
| a layer of them occurs where bipolar cells synapse with ganglion cells |
|
|
Term
| How many cones and rods does the retina have? |
|
Definition
| 6 million cones and 125 million rods |
|
|
Term
| Where are the densities of cones and rods at a max? |
|
Definition
| cones: fovea, rods: lateral and nasal borders |
|
|
Term
|
Definition
|
|
Term
|
Definition
| sharpness of vision, directly correlated with cone density |
|
|
Term
|
Definition
| macula doesn't work the best, and the photoreceptors start to die, leading to lesions and loss of vision; dry: RPE isn't working, wet: blood vessels are growing in |
|
|
Term
| Where does photoreception occur? |
|
Definition
| at the outer segment of rods and cones |
|
|
Term
| Light energy is in the form of _____. |
|
Definition
|
|
Term
| What wavelengths are our eyes sensitive to? |
|
Definition
| 400-700 nm (spectrum of visible light) |
|
|
Term
| The outer segments of rods and cones have _____ that contain _____. |
|
Definition
membranous plates and discs
visual pigments (special organic compounds) |
|
|
Term
| What absorbs photons that aren't absorbed by visual pigments? |
|
Definition
|
|
Term
| The pigment epithelium has _____. |
|
Definition
|
|
Term
| The outer segment of the pigment epithelium has what (having to do with cones and rods)? |
|
Definition
| cones with infolding discs of the plasma membrane and rods that are independent entities |
|
|
Term
| The inner segment of the pigment epithelium contains what? |
|
Definition
|
|
Term
| The inner segment of the pigmented epithelium is responsible for what? |
|
Definition
| all cell functions other than photoreceptors |
|
|
Term
| What are visual pigments derived from? |
|
Definition
| the compound rhodpsin, which is visual purple (which is made of the protein opsin bound to the pigment retinal) |
|
|
Term
| In photoreception, when light strikes a visual pigment, retinal molecule does what? |
|
Definition
| changes shape, which leads to a change in permeability of outer segment |
|
|
Term
| What is the key to transduction in the eye? |
|
Definition
| permeability because it converts light energy into a nerve impulse |
|
|
Term
| Part 1 of the photoreception process |
|
Definition
1. light is absorbed -> retina changes to a more linear shape -> activation of opsin
2. opsin activation changes the permeability of the outer segment to Na+ -> rate of neurotransmitter release by inner segment at its synapse with a bipolar cell
3. change in bipolar cell activity are detected by 1+ ganglion cells |
|
|
Term
| What does the location of the stimulated ganglion cells indicate? |
|
Definition
| the specific portion of the retina stimulated by arriving photons |
|
|
Term
| Part 2 of the photoreception process |
|
Definition
4. rhodopsin absorbs photon and begins to breakdown into retinal and opsin (bleaching)
5. retinal converted to original shape (requires ATP)
6. retinal recombines with opsin -> rhodopsin now ready to repeat cycle |
|
|
Term
| What happens to photoreceptors during regeneration? |
|
Definition
| they are inactivated (after exposure to bright light) |
|
|
Term
| What are the three types of cones and their abundance? |
|
Definition
| blue (16%), green (10%), and red (74%) |
|
|
Term
| What is different about each type of cone? |
|
Definition
| they each have a different form of opsin that is sensitive to a different range of wavelength |
|
|
Term
| What is perceived when all three types of cones are stimulated? |
|
Definition
|
|
Term
| If rods but not cones are stimulated, what is perceived? |
|
Definition
|
|
Term
| What does color blindness result from? |
|
Definition
| lack of 1 of more cone pigments |
|
|
Term
| The most common forms of color blindness are _____. |
|
Definition
|
|
Term
| What type of color blindness is very rare? |
|
Definition
|
|
Term
|
Definition
| lack either red or green cones; 2% of males |
|
|
Term
|
Definition
| distribute info from each eye to both cerebral hemispheres |
|
|
Term
| Where do visual pathways begin? |
|
Definition
| at photoreceptors in the retina |
|
|
Term
| What does each photoreceptor do, and what happens when they're stimulated? |
|
Definition
monitors a specific receptor field
passes the info through a bipolar cell and to a ganglion cell |
|
|
Term
| How many ganglion cells are there? |
|
Definition
|
|
Term
| After the optic nerve penetrates the wall of the eye, where does it go? |
|
Definition
| the diencephalon (the optic nerves reach it at the optic chiasm) |
|
|
Term
| How do the fibers proceed from there? |
|
Definition
| Half go to the lateral geniculate nucleus on the same side of the brain, and half cross over to opposite side |
|
|
Term
| Where does the visual info go from the lateral geniculate nucleus? |
|
Definition
| the occipital cortex of the cerebral hemisphere on that side |
|
|
Term
|
Definition
| the bundle of projection fibers linking each lateral geniculate nucleus with the visual cortex |
|
|
Term
| The fovea of each eye are about ____ cm apart, so _____. |
|
Definition
5-7.5
each eye receives a slightly different image and the visual images overlap |
|
|
Term
| The left cortex gets ____, and vice versa. |
|
Definition
|
|
Term
| The basic (3 way) visual path is what? |
|
Definition
| receptors -> bipolar cells -> ganglion cells |
|
|
Term
| What can accommodation problems result from? |
|
Definition
| abnormalities in the cornea, lens, or the shape of the eye |
|
|
Term
| What is normal vision called? |
|
Definition
|
|
Term
|
Definition
| nearsightedness; the image of a distant object is projected in front of the retina due to a deep eyeball or too great of a lens curvature |
|
|
Term
|
Definition
| diverging lenses (concave surface that spreads light rays apart as if the object were closer) |
|
|
Term
|
Definition
| farsightedness; too shallow of an eyeball or too flat of a lens, so the ciliary muscle must contract to focus even a distant object on the retina, and at close range the lens can't provide enough refraction to focus an image on the retina |
|
|
Term
| How is hyperopia treated? |
|
Definition
| with a converging lens (convex surface that provides additional refraction needed for focusing on a close object) |
|
|
Term
| photorefractive keratectomy (PTK) |
|
Definition
| computer-guided laser shapes the cornea to exact specifications; tissue is removed down to about 10% of the cornea, and it takes < 1 minute |
|
|
Term
| laser-assisted in-situ keratomiteusis (LASIK) |
|
Definition
| interior layers of the cornea are reshaped and covered by a flap of the normal corneal epithelium; most common refractive surgery, and ~70% of patients achieve normal vision |
|
|
Term
|
Definition
| lens loses transparency (opaque) from injury, radiation, or a reaction to drugs |
|
|
Term
|
Definition
| most common type; due to old age |
|
|
Term
| How can a damaged lens from cataracts be fixed? |
|
Definition
| it can be replaced by a synthetic lens |
|
|
Term
|
Definition
| a process in photoreception where rhodopsin absorbs photon and begins to breakdown into retinal and opsin |
|
|
Term
|
Definition
| irregularities/unequal curvature of the lens or cornea that causes blurred vision |
|
|
Term
|
Definition
| elasticity of the lens decreases with age, which makes it harder to focus for near vision |
|
|
Term
|
Definition
| alteration in the curvature of the lens to focus an image on the retina |
|
|
Term
| cranial nerve of each extrinsic eye muscle |
|
Definition
| superior rectus (III), inferior rectus (III), medial rectus (III), lateral rectus (VI), superior oblique (IV), inferior oblique (III) |
|
|
