Eye Anatomy & Physiology Flashcards
(131 cards)
1
Q
where is the eyeball located?
A
in orbits on either side of the nasal cavity
2
Q
what provides protective cushioning and keeps the eyeball in proper position?
A
adipose tissue
3
Q
what’s another word for eyelids?
A
palpebrae
4
Q
what are the eyelids job?
A
to prevent access by foreign objects and distribute tears during blinking
5
Q
what are the 3 parts of the eyelid?
A
tarsal plates, tarsal glands, and lacrimal caruncle
6
Q
what are tarsal plates?
A
thin pieces of dense regular collagenous connective tissue
7
Q
what are the tarsal plates job?
A
to reinforce each eyelid
8
Q
what are tarsal glands?
A
modified sebaceous glands located with tarsal plates
9
Q
what is the tarsal glands job?
A
to secrete oil that prevents eyelids from sticking together
10
Q
what is the lacrimal caruncle?
A
fleshy structure at medial commissure
11
Q
what is the lacrimal caruncles job?
A
secretes whitish lubricating substance
12
Q
eyebrow’s purpose?
A
to prevent perspiration from running into the eyes; reduce glare from bright light; important for facial expressions
13
Q
eyelash’s purpose?
A
associated with sensitive nerve endings so causes blinking when objects touch them; reduces eye injury
14
Q
what is the conjunctiva?
A
thin continuous epithelial membrane; translucent membrane in which tiny blood vessels can be seen
15
Q
what are the 2 layers of the conjunctiva?
A
palpebral and ocular conjunctiva
16
Q
palpebral conjunctiva purpose?
A
covers eyelid inner surface
17
Q
ocular conjunctiva purpose?
A
covers anterior white part of eyeball
18
Q
job of the lacrimal apparatus?
A
produces and drains tears from eye
19
Q
where is the lacrimal gland?
A
in superolateral region of orbit
20
Q
job of the lacrimal gland?
A
releases tears and mucus into tiny ducts; lubricates and washes away debris
21
Q
what is the passageway of tears?
A
lacrimal gland – lacrimal punctum – lacrimal sac – nasolacrimal duct
22
Q
what is the lacrimal puncta?
A
tiny openings in medial edge of each eyelid
23
Q
where is the lacrimal sac?
A
located in small depression in lacrimal bone
24
Q
what are the extrinsic eye muscles?
A
superior, inferior, lateral, medial rectus, superior oblique, inferior oblique, CN IV (trochlear), CN VI (abducens), and CN III (oculomotor)
25
purpose of superior oblique?
contraction depresses eye and moves it laterally
26
purpose of inferior oblique?
contraction elevates and moves eye laterally
27
what is Strabismus?
aka lazy eye; disorder present at birth; eyeballs are not properly aligned with one another
28
what are the 3 tissue layers of the eyeball?
fibrous, vascular, and neural
29
what does the fibrous layer consist of?
connective tissue; sclera and cornea
30
what does the vascular layer consist of?
blood vessels; iris, ciliary body, and choroid
31
what does the neural layer consist of?
photoreceptors; retina
32
what is the fibrous layer?
outermost layer
33
what is the sclera?
white part of the eye; covers nearly the entire eye; irregularly arranged collagen fibers
34
purpose of the sclera?
resists deformation from external or internal forces to maintain shape
35
what is the cornea?
continuous with sclera anteriorly; translucent instead of opaque due to parallel arrangement of collagen fibers
36
purpose of the cornea?
avascular (no blood vessels); allows light to pass into the eyeball
37
what is the vascular layer?
middle layer; absorbs excess light
38
what is the choroid?
coat; contains capillaries and pigment
39
purpose of the choroid?
minimizes scattering of incoming light rays
40
purpose of the ciliary body?
contains ring of smooth muscle that surrounds lens
41
what are suspensory ligaments?
connect ciliary body to lens
42
purpose of suspensory ligaments?
allows for contraction and relaxation; changes shape of lens to focus light
43
what is the iris?
colored region of anterior eye
44
what is the pupil?
opening in center of iris through which light enters the eyeball
45
where is the pupillary sphincter and pupillary dilator muscles?
in iris
46
purpose of pupillary sphincter muscle?
CONTRACTS TO MAKE PUPIL SMALLER (increased light intensity); contracts during parasympathetic stimulation; reduces size of pupil; restricts amount of light entering eyeball
47
purpose of pupillary dilator muscle?
CONTRACTS TO MAKE PUPIL LARGER (decreased light intensity); contracts during sympathetic activation; allows pupil to increase in size; more light enters eyeball
48
what is the neural layer?
innermost layer of eyeball; incomplete layer; only deep to choroid coat
49
what are the 2 portions of the neural layer?
superficial and deep layers
50
what is the superficial layer?
consists of thin, pigmented epithelium
51
purpose of the superficial layer?
reduces light scattering and nourishes photoreceptors
52
what is the deep layer?
consists of photoreceptor cells and cells that form optic nerve
53
purpose of photoreceptor cells?
detect and transduce light stimuli into electrical signals
54
what are the photoreceptors in the neural layer called?
rods and cones
55
what do rods allow us to see?
black and white vision in low light levels and peripheral vision
56
what do cones allow us to see?
high-acuity color vision in higher light levels
57
what is the ora serrata?
visible boundary between anterior edge of retina and posterior edge of ciliary body
58
what is the macula lutea?
contains large number of photoreceptors
59
what is the fovea centralis?
central region of macula lutea; contains large number of cones tightly packed together
60
purpose of the fovea centralis?
allows for detailed vision and ability to focus on object
61
what is macular degeneration?
leads to progressive loss of visual acuity; particularly of visual field; may also cause visual distortion and changes in color perception
62
what is the optic disc?
aka blind spot; does not contain photoreceptors or capture visual images
63
what are the lens?
slightly flattened sphere behind pupil and iris; contains cells (lens fibers) that lack nuclei; tightly packed; translucent; connected to ciliary body by suspensory ligaments
64
purpose of lens?
focuses light on retina from objects near eye
65
the eyeball is divided by?
the lens and ciliary body
66
what are the cavities of the eye?
posterior and anterior
67
what is the posterior cavity?
larger cavity BEHIND lens; contains vitreous humor
68
what is vitreous humor?
made mostly of collagen and water
69
purpose of vitreous humor?
presses retina against choroid; helps maintain eyeball shape
70
what is the anterior cavity?
in FRONT of lens and ciliary body; contains posterior & anterior chambers and scleral venous sinus
71
where is the posterior chamber?
between lens and iris
72
where is the anterior chamber?
between iris and cornea
73
what is aqueous humor?
watery fluid secreted by ciliary body; flows from posterior chamber through pupil into anterior chamber
74
what is the scleral venous sinus?
aka canal of Schlemm; blood vessel network at anterior edge of iris
75
purpose of the scleral venous sinus?
drains aqueous humor out of anterior chamber
76
what is vision?
perception of light reflected by various objects; determine object's size, shape, and color; interpret object distance, rate, and direction of movement
77
what is electromagnetic radiation?
energy traveling in range of wavelengths (nanometers)
78
what is visible light?
range of wavelengths that human eye can detect as range of particular colors
79
blue and violet =
shorter wavelengths
80
red =
longer wavelengths
81
what is a photon?
basic unit of light energy; stimulates photoreceptors in retina
82
what is refractive index?
amount of refraction
83
air refractive index =
1; density similar to air so light does not refract
84
water refractive index =
greater than 1; density greater than air so light refracts
85
greater angle =
greater refraction
86
what are the convex lens?
surface that bulges outward in middle region
87
purpose of convex lens?
causes light rays to bend inward or converge as they pass through
88
what are concave lens?
thicker on edge and depressed in middle region
89
purpose of concave lens?
causes light rays to diverge or spread out (unfocused)
**rays converging on focal point are said to be focused
90
light rays focus on which part of the eye for clear vision?
retina
91
when light hits the lens, what happens?
fine tuning and adjustment; change shape
92
when light hits the cornea, what happens?
refractive index close to water
93
what is emmetropic state?
eye is relaxed and focusing on distant objects; lens is in normal flattened shape; parallel light rays are minimally refracted by cornea and focused on retina; tension on suspensory ligaments
94
what is accommodation?
objects closer to the eye need more refraction; lens become more thickened; suspensory ligaments slacken
95
ability to focus on near objects also needs
pupillary constriction and convergence
96
what is pupillary constriction?
limits amount of scattered light that makes objects appear blurry; enters edge of lens; objects appear more focused
97
what is convergence?
process by which eyeballs move more medially to direct light rays on to photoreceptor-dense region of fovea
98
what are the errors of refraction?
accommodation affected due to aging lens or shape of eyeball; hyperopia, myopia, and astigmatism
99
what is near point of accommodation?
increases with age
100
what is presbyopia?
near point of accommodation is greater than 10-20 inches; corrected with reading glasses or bifocals
101
what is hyperopia?
farsightedness; eyeball is too short or cornea is too flat; focuses behind retina; causes blurry vision when looking at close objects
102
what is the correction for hyperopia?
convex lenses causing more light to converge on retina; LASIK
103
what is myopia?
nearsightedness; distance between cornea and lens is too great or cornea is too curved; light is focused in front of retina, blurring objects viewed at a distance
104
what is the correction for myopia?
concave lenses diverge incoming light before it contacts lens; LASIK
105
what is astigmatism?
curvature of lens or cornea is irregular; light rays are not evenly refracted; blurred vision at all distances
106
what are the corrections for astigmatism?
corrective lenses that adjust for specific abnormal corneal or lens curvature; LASIK
107
what does the retina's structure inner layer consist of?
photoreceptors; rods and cones
108
function of cones?
function best in bright light for processing high-resolution color vision
109
function of rods?
do not detect colors; most sensitive in low light and as component of peripheral vision
110
what does the retina's structure outer layer consist of?
vitreous humor; bipolar, retinal ganglion, and horizontal and amacrine cells
111
what are bipolar cells?
neurons that communicate with retinal ganglion cells
112
what are retinal ganglion cells?
in anterior-most region of retina; axons form optic nerve (CN II)
113
what are horizontal and amacrine cells?
involved in image processing
114
what consist of rod structure?
cylindrical outer segments, rhodopsin, and retinal
115
what are cylindrical outer segments?
contain 100s of flattened discs containing pigment Rhodopsin that absorbs light; do not distinguish between different wavelengths of light
116
what is Rhodopsin?
composed of protein opsin and pigment retinal; pigment that absorbs light
117
what is retinal?
derived from vitamin A; pigment
118
what consist of cone structure?
iodopsin and photopsin
119
what is iodopsin?
composed of retinal and protein photopsin
120
what is photopsin?
similar to opsin but has slightly altered structure; allows it to absorb diferent wavelengths of light
121
what are the 3 forms of photopsin?
blue, green, or red wavelengths
122
characteristics of adaptation to darkness?
cones can not function due to light suddenly reduced; rods are slow to degenerate enough rhodopsin to function; retina sensitive to light; up to 40 minutes to be completely functional
123
characteristics of adaptation to light?
bleaches rods and cones, blinding glare; rods become nonfunctional (rhodopsin is bleached as fast as it is regenerated); cones can regenerate functional pigments faster, able to respond within few minutes as their sensitivity decreases
124
what is the visual field?
what is seen with that eye alone, with both eyes open; field is divided into left and right with focal point in center
125
what is the retina's role in the visual pathway?
detects visual stimuli from portions of right and left visual fields
126
what is stereoscopic vision?
depth perception; eyes face anteriorly (binocular); brain compares overlapping images to determine distance an object is from eyes
127
what is depth perception?
distance an object is from eyes
128
what is the consensual pupillary response?
constriction of both pupils in response to light entering left or right pupil only; reflectively to prevent damage to retina, optic nerve, and brainstem
129
what are the optic tracts?
where axons exit the optic chiasma
130
what is the primary visual cortex?
occipital lobe
131
what is the optic chiasma?
axons carrying visual stimuli cross here; all stimuli from right visual field are processed by left hemisphere and vice versa
