Lab 10 vision and the eye study Flashcards
(113 cards)
1
Q
Eyes enable us to see in 3 dimensions with
A
stereoscopic vision
2
Q
Sterioscopic vision - This describes the ability of the visual brain to register a sense of three-dimensional shape and form from visual inputs. In current usage, stereoscopic vision often refers uniquely to the sense of
A
depth derived from the two eyes.
3
Q
Eyelids also called
A
palpebrae
4
Q
Eyelids thin, skin-
covered folds that
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protect eye anteriorly
5
Q
Eyelids Separated at
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palpebral fissure (slit)
6
Q
Eyelids Meet in corners at
A
medial and lateral canthus (commissures)
7
Q
Lacrimal caruncle located at medial commissure contains
A
oil and sweat glands
8
Q
Lubricating glands associated with eyelids
A
Tarsal (Meibomian) glands
9
Q
Tarsal (Meibomian) glands Modified sebaceous glands produce
A
oily secretion that lubricates lid and eye
10
Q
Conjunctiva - Transparent mucous membrane that produces
A
a lubricating mucous secretion
11
Q
Lacrimal gland is located in orbit above lateral end of eye and secretes
A
lacrimal secretion (tears)
12
Q
lacrimal secretion (tears),
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a dilute saline solution containing mucus, antibodies, and antibacterial lysozyme
13
Q
Blinking spreads tears toward
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medial commissure, where they enter lateral puncta
14
Q
Flow
A
- the lacrimal gland produces and secretes tears (lacrimal secretions) 2. tears enter the conjunctival sac via the excretory ducts of the lacrimal gland 3. tears flow down and across the eyeball 4. tears enter the lacrimal canaliculi at openings called lacrimal puncta 5. tears drain into the lacrimal sac 6. from the lacrimal sac tears empty via the nasolacrimal duct into the inferior meatus of the nasal cavity
15
Q
Six straplike extrinsic eye muscles Originate from
A
bony orbit and insert on eyeball
16
Q
Extrinsic eye muscles Enable eye to
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follow moving objects, maintain shape of eyeball, and hold it in orbit
17
Q
Four rectus muscles originate from common tendinous ring; names indicate movements
A
Superior, inferior, lateral, and medial rectus
18
Q
Two oblique muscles move eye in vertical plane and rotate eyeball
A
Superior and inferior oblique muscles
19
Q
lateral rectus moves eye
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laterally
20
Q
lateral rectus muscle cotrols what cranial nerve
A
Vl (abducens)
21
Q
Medial rectus moves eye
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medially
22
Q
Medial rectus muscle cotrols what cranial nerve
A
lll (oculomotor)
23
Q
superior rectus elevates eye and turns it
A
medially
24
Q
superior rectus muscle cotrols what cranial nerve
A
lll (oculomotor)
25
inferior rectus depresses eye and turns it
medially
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inferior rectus muscle cotrols what cranial nerve
lll (oculomotor)
27
inferior oblique elevates eye and turns it
laterally
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inferior oblique muscle cotrols what cranial nerve
lll (oculomotor)
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superior oblique depresses eye and turns it
laterally
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superior oblique muscle cotrols what cranial nerve
lV (trochlear)
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Nasal cavity mucosa is continuous with mucosa of lacrimal duct system, so a cold or nasal inflammation often causes
lacrimal mucosa to swell
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Swelling constricts the ducts and prevents tears from draining, causing
“watery” eyes
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Wall of eyeball contains three layers
* Fibrous layer
* Vascular layer
* Inner layer
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Internal cavity filled with fluids called
humors
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Lens separates internal cavity into
anterior and posterior segments
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Fibrous layer Outermost layer;
dense avascular
| connective tissue
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Fibrous layer Two regions
sclera and cornea
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Sclera
Opaque posterior region
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Sclera Protects and
shapes eyeball
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Sclera Anchors
extrinsic eye muscles
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Cornea Transparent anterior one-sixth of
fibrous layer
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Cornea Forms clear window that lets light enter and
bends light as it enters eye
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Numerous pain receptors contribute to
blinking and tearing reflexes
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Vascular layer Middle pigmented layer of eye, also
| called
uvea
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Vascular layer Three regions
choroid, ciliary body, and iris
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Choroid region Posterior portion of
uvea
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Choroid region Supplies blood to
all layers of eyeball
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Brown pigment absorbs light to prevent scattering of light, which would cause
visual confusion
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Iris Colored part of eye that lies between
cornea and
| lens, continuous with ciliary body
50
Pupil: central opening that regulates
amount of light entering eye
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Close vision and bright light cause sphincter pupillae (circular muscles) to contract and pupils to constrict;
parasympathetic control
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Distant vision and dim light cause dilator pupillae (radial muscles) to contract and pupils to dilate;
sympathetic control
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Changes in emotional state—pupils dilate when subject matter is appealing or
requires problem- solving skills
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Anteriorly, choroid becomes
Ciliary body
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Ciliary body Thickened ring of
tissue surrounding lens
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Consists of smooth muscle bundles
ciliary muscles, that control shape of lens
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Capillaries of ciliary processes secrete fluid for
anterior segment of eyeball
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Ciliary (suspensory ligament) extends from
ciliary processes to lens
| • Holds lens in position
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Retina originates as an
outpocketing of brain
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Inner layer (retina) Contains: 3
* Millions of photoreceptor cells that transduce light energy
* Neurons
* Glial cells
61
Inner layer (retina) Delicate two-layered membrane
* Outer pigmented layer
| * Inner neural layer
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Inner layer (retina) Pigmented layer of the retina Functions: 3
* Absorbs light and prevents its scattering
| * Phagocytizes photoreceptor cell fragments • Stores vitamin A
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Neural layer of the retina
Transparent layer that runs anteriorly to margin of ciliary body
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Neural layer of the retina Composed of three main types of neurons
Photoreceptors, bipolar cells, ganglion cells
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Signals spread from photoreceptors to
bipolar cells to ganglion cells
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Ganglion cell axons exit eye as
optic nerve
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Retinal Modifications: Optic disc
Site where optic nerve leaves eye
68
Optic disc Lacks photoreceptors, so referred to as
blind spot
69
Retina has quarter-billion photoreceptors that cannot
respond to light
70
Internal chambers and fluids 2
Posterior segment Anterior segment
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Anterior segment Iris divides
anterior segment into two chambers
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the two chambers
* Anterior chamber
| * Posterior chamber
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Entire anterior segment contains
aqueous humor
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aqueous humor a plasma like fluid continuously formed by
capillaries of ciliary processes
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Drains via scleral venous sinus (canal of Schlemm) Supplies nutrients and oxygen mainly to lens and cornea but also to
retina, and removes wastes
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circulaiton of aqueous humor 3
1. aqueous humore forms by filtration from the capilaries in the ciliary processes 2. aqueous humor flows from the posterior chamber through the pupil into the anterior chamber some also flow through the vitreous humor 3. aqueous humor is reabsorbed into the venous blood by the scleral venous sinus
77
Posterior segment Contains
vitreous humor
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vitreous humor a fluid that 4
* Transmits light
* Supports posterior surface of lens
* Holds neural layer of retina firmly against pigmented layer
* Contributes to intraocular pressure
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Lens
Biconvex, transparent, flexible, and avascular
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Lens Changes shape to precisely focus light on
retina
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Lens two regions
Lens epithelium
| Lens fibers
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Lens epithelium
anterior region of cuboidal cells that differentiate into lens fiber cells
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Lens fibers
form bulk of lens
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Lens fibers are continually added, so lens becomes
more dense, convex, and less elastic with age
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Clouding of lens
Consequence of aging, diabetes mellitus, heavy
| smoking, frequent exposure to intense sunlight
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Clouding of lens 3
* Some congenital
* Crystallin proteins clump
* Lens can be replaced surgically with artificial lens
87
Refraction
bending of light rays
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Light travels in straight lines (rays) at a constant speed until it
reaches a medium with a different density
89
Light rays bend (refraction) during passage through structures of
differing density
90
n eye, light is bent (refracted) three times – passing through these structures and the vitreous and aqueous humor
1. Entering cornea or air
| 2. Entering lens from cornea 3. Leaving lens
91
Refraction – illustration – going from
air (less dense) to water (more dense)
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Lens highly
elastic
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Lens Shape can change via contractions of
ciliary smooth muscles
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Lens Accommodates for light from
different distances
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Looking at close objects, Ciliary muscles
contract, decrease tension suspensory ligaments
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Problems associated with refraction related to eyeball shape 3
Myopia
hyperopia
astigmatism
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Myopia (nearsightedness)
Eyeball is too long, so focal point is in front of retina
| Corrected with a concave lens
98
hyperopia (farsightedness)
Eyeball is too short, so focal point is behind retina Corrected with a convex lens
99
astigmatism
Unequal curvatures in different parts of cornea or lens
| Corrected with cylindrically ground lenses or laser procedures
100
Axons of retinal ganglion cells form
optic nerve
101
Medial fibers from each eye cross over at the
optic chiasma
102
The lateral field of vision fibers do not cross over at the
optic chiasma
103
After leaving the optic chiasm they continue on as
optic tracts
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which means each optic tract: 2
* Contains fibers from lateral (temporal) aspect of eye on same side and medial (nasal) aspect of opposite eye, and
* Each carries information from same half of visual field
105
Paired Optic Tracts run posteriorly around
hypothalamus sending axons to synapse with neurons in Lateral Geniculate Nuclei of thalamus
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Function: balance and combine retinal input for
delivery to visual cortex
107
Axons of Lateral Geniculate Nuclei form Optic Radiation of fibers in
white matter
108
Optic radiation of fibers project to primary visual cortex in
occipital lobes
109
Rods and Cones are
photoreceptors
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photoreceptors are
modified neurons
111
Rods are more numerous; used for
dim light and peripheral vision
112
Cones used for bright light and provide for
high-resolution and color vision
113
Responsible for understanding common eye disorders pointed out in lab manual
• Find referred to in textbook
• Understand dark and light adaptation referred to in lab manual
• Understand other homeostatic imbalances associate with eye in lab book pg. 204
• I may use any of the figures in this presentation in the lab practical with the exception of figure 15.19a (visual pathway – will use the one from the lab manual)
