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Anat-Visual System

accessory structures of the eye eyebrows, eyelids, eyelashes, lacrimal (tear) glands
visual system components eye, accessory structures of the eye, optic (CNII)
transmission path of visual sensory information sensory information travels along the optic nerve to the thalamus and then to the occipital lobe where the information is processed
eyebrows function prevent perspiration from running into the eyes (channel it away), provides a little bit of shade and some bony protection
eyebrows location bony ridges forming the superior edge of the orbit
eyelids palpebrae (upper and lower)
eyelid function protection and lubrication (blinking moves tear fluid onto the surface of the eye)
lacrimal caruncle location where the eyelids meet on the medial side of the eye
lacrimal caruncle function has sebaceous and sweat glands that produce a water and oil mix that helps to reduce water loss and makes lubrication for the eye
extrinsic eye muscles number/function 6/ move the eye in the orbit
lacrimal apparatus function contains the lacrimal gland; produces, collects, and drains lacrimal fluid (tears)
lacrimal gland location above the eye in the superior region of the orbit
lacrimal gland function produces tears that lubricate and prevent water loss, innervated by the facial nerve (CNVII)
pathway of tears produced in the lacrimal gland and drains into the nasal cavity via the lacrimal groove and a channel down to the nose
conjunctiva structure/location thin epithelial layer of mucous membrane over the inner surface of the eyelids and the anterior surface of the eyeball (except for the cornea), has associated blood vessels (bloodshot eyes and pink eye)
three coats/tunics of the eye fibrous, vascular, neural
Parts of the fibrous tunic sclera, cornea
parts of the vascular tunic choroid, ciliary body, and iris
parts of the neural layer retina
sclera structure made up of dense irregular connective tissue, fairly thick, white outer layer, continuous with the cornea
sclera function maintains shape, protects internal structures, provides muscle attachment point for the 6 eye muscles
cornea structure no blood vessels so they don't scatter light rays, transparent and curved, gets oxygen from dissolved oxygen in the fluid covering it
cornea function first structure of the eye that light passes through (allows light to enter the eye), does most of the refracting (bending) of light rays
iris location between the cornea (immediately behind it) and the lens
iris function controls light entering the pupil by controlling its size (via the oculomotor nerve)
iris structure made of smooth muscle with and opening (pupil) and pigment cells that give us our eye color
ciliary muscles function control the shape of the lens to focus on objects
ciliary muscles location found inside the ciliary body, connected by suspensory ligaments
ciliary muscles structure made of smooth muscle
choroid structure contains capillaries and melanin pigment (produced by melanocytes)
choroid function helps to absorb stray light rays, forms most of the vascular tunic
retina structure very thin; contains photoreceptor cells sensitive to light, macula lutea, fovea centralis, and optic disc; connected to the optic nerve
macula lutea structure/function yellowish region with a concentration of cones
fovea centralis structure/function "dimple" on the macula lutea with the most concentrated amount of cones, area of the greatest visual acuity, eye is adapted to focus here
optic disc structure/function blind spot where blood vessels and the optic nerve enter the eye, no photoreceptors here, brain fills in the missing part of the image
cones function/location provide color vision and give us visual acuity; found within the fovea centralis
visual acuity the ability to see fine details
rods function/location sensitive to low light conditions; scattered throughout the rest of the retina (other than the fovea centralis)
anterior cavity location/contents anterior to the lens; contains aqueous humor
posterior cavity location/contents posterior to the lens, larger of the two cavities; contains vitreous humor
lens location/structure held by suspensory ligaments attached to ciliary muscles; transparent and biconvex
structures involved in focusing and accommodation cornea, lens, suspensory ligaments, ciliary body
far vision distance 20 feet or more from the eye
near vision distance closer than 20 feet from the eye
actions that focus far vision parallel light rays are bent inwards by the cornea, ciliary muscles relax to make the "hole" larger, the suspensory ligaments taut, and the lens flatter so that it only refracts a small bit (cornea already did most of the work)
distance of objects we are adapted to looking at far objects
accommodation focusing on near objects
actions that focus near vision diverging light rays are partially refracted by the cornea, ciliary muscles contract, ciliary body moves towards the lens, suspensory ligaments relax, and tension on the lens is released to make it thicker and more spherical so it can refract more
suspensory ligaments function attach to the lens at its periphery and transmit tension that enables the lens to change shape
myopia causes eyeball is too long and rays from distant objects focus anterior to the retina
hyperopia causes eyeball is too short so light rays from close objects focus posterior to the retina
presbyopia causes lens becomes less resilient and less able to become spherical with old age-stays in the default position
astigmatism causes due to unequal curvatures along the cornea or lens
retinal detachment causes caused when the layers of the retina separate due to head trauma or stretching of the retina
retinal detachment symptoms fluid accumulates between the layers and causes "floaters", flashes of light, and decreased, watery, or wavy vision
astigmatism symptoms causes unequal focusing and blurred images at all distances
presbyopia symptoms difficulties focusing close-up objects
hyperopia symptoms troubles seeing close-up objects, farsightedness
myopia symptoms troubles seeing far-away objects, nearsightedness
glaucoma causes fluid and pressure build-up in the anterior chamber, which causes a posterior dislocation of the lens and a build-up of pressure in the posterior chamber
glaucoma symptoms reduced field of vision, dim vision, and halos around lights; ocular distortion or pain
cataract causes aging, sometimes caused by diabetes, intraocular infections, excessive UV exposure, or glaucoma
cataract symptoms small opacities in the lens that result in difficulty focusing on close objects, reduced visual clarity, clouding of the lens, "milky" vision, and reduced intensity of colors, also causes blindness
macular degeneration causes physical degeneration of the macula lutea, caused by age, diabetes, ocular infection, heredity, or trauma to the eye
macular degeneration symptoms blindness, photoreceptor loss, thinning of the pigmented layer of the retina, bleeding, capillary proliferation, scar tissue formation, loss of visual acuity, straight lines appear wavy, diminished color perception, floaters or dark areas, dry eyes
Created by: Jean-O