Lecture Outline #19: Special Senses: Eye

Question 1

the eye

Answer 1

extension of the brain, diencephalon is pushed out

Question 2

fibrous tunic

Answer 2

sclera & cornea

Question 3

sclera

Answer 3

dense CT - white of the eye
attachment site for muscles of the eye
elastic/mechanical support for globe

Question 4

cornea

Answer 4

modified sclera - 1/6th of globe
avascular, translucent bulge @ anterior surface, gets nutrients through humor and air in the environment
bends light to focus on retina

Question 5

optical axis

Answer 5

straight line from center of pupil to back

Question 6

vascular tunic

Answer 6

choroid, ciliary body (m. & sus ligs), iris

Question 7

choroid

Answer 7

inner posterior surface of globe
vascular - nourish the retina
black pigmentation absorbs stray light

Question 8

ciliary body

Answer 8

CN III
ciliary m. - smooth m. of radial and circular fibers, contraction reduces tension of sus ligs, doesn’t pull on sus ligs
suspensory lig - zonular fibers, an/post to lens, attach through ciliary m. to sclera

Question 9

ora serrata

Answer 9

junction of choroid and cil body
where choroid and retina merge @ non-photic aspect of retina

Question 10

iris

Answer 10

smooth m - circular & radial m.s (antagonists
- pupillary constrictor m. (sphincter) parasym stimulation - pupil contraction
- pupillary dilator m.s (radial) sym stimulation - pupil dilation
regulates amount of light that passes to retina
separates ant cavity into ant/post chambers

Question 11

anterior cavity

Answer 11

filled with aqueous humor (~CSF) - helps control intra-ocular pressure, produced by the ciliary process, returned to blood supply via Canal of Schlemm (venous drainage to dural sinuses) by going through pupil.
- anterior chamber - ant to iris
- posterior chamber - post to iris, ant to lens

Question 12

posterior cavity

Answer 12

filled with vitreous humor - gel-like fluid that assist sclera in maintaining shape of globe
posterior to lens

Question 13

sus lig

Answer 13

barrier btw. ant/pot cavities
composed of two fused membranes
lens is sandwiched/suspended btw. layers

Question 14

glaucoma

Answer 14

circulation of aqueous humor is blocked so it stays btw iris & cornea, increased pressure - damage to nerve, compresses BVs and pushes on retina
cloudy/gray-green eye, assoc. with high blood pressure

Question 15

neural tunic - matter

Answer 15

retina
gray matter - deep, rods and cones
white matter - superficial, vasculature/ganglia

Question 16

retina - posterior pigmented layer

Answer 16

dark pigmentation absorbs stray light
supports anterior neural layer
integration center

Question 17

retina - anterior neural layer

Answer 17

contain 9 layers of cells
around 130 mill photoreceptors
houses neurons, neuroglia, ganglia, BVs, rods, cones

Question 18

photoreceptors

Answer 18

not chemoreceptors
rods - gray-scale, dim light, around 125 mill per
cones - color vision, around 6 mill per, take lots of energy to activate, absence of one type = color blindness

Question 19

light flow

Answer 19

retina - optic n. - optic chiasm - optic tract - lateral geniculate nuclei of the thalamus, superior colliculi - primary vision cortex of the occipital lobe

Question 20

macula lutea & fovea centralis

Answer 20

center of visual axis
fovea is the focal pt, has the highest # of cones for greatest resolution and is the pit inside the macula

Question 21

blind spot

Answer 21

optic disc, 10 degrees off and medial to fovea
pt where optic n. exits globe and BVs enter/exit, no photoreceptors

Question 22

red and cat eye

Answer 22

red - vasculature in retina
cat - additional layer = tapetum lucidum - reflected disc that activates photoreceptors

Question 23

globe of the eye & retina

Answer 23

formed as lateral diverticula of the di, each diverticulum collapses to form eye-cup
each retina retains early neural tube arrangement and appears to be installed backwards

Question 24

clinical implications/mechanical limitations of eye

Answer 24

1. light receptors point wrong way
2. receptors buried behind a layer
3. blind spot
   = 70% of image is lost

Question 25

pineal gland

Answer 25

acts as third eye same make-up as retina out pocketing of the di (diverticulum)

Question 26

photic sneeze reflex

Answer 26

when look at sun = sneeze autosomal dominant trait, 20% Caucasian and female, protective reflex (450mph) II retina - III iris - III - V- bs

Question 27

lens

Answer 27

thick biconcave disc of specialized fibers avascular - get aqueous/vitreous humor/nutrients from ant/post cavities. suspended from sclera by sus ligs

Question 28

accommodation

Answer 28

ability to focus, lens fine tunes image on fovea within center of macula lutea close objects - c m. contracts, ligs sag = lens bulges far objects - c m. relaxes, ligs tighten = lens thins

Question 29

presbyopia, myopia, hyperopia

Answer 29

pres - lens proteins become stiff w/ old age, can't focus on near object, refractive properties change myo - nearsightedness hyp - farsightedness

Question 30

cataracts

Answer 30

abnormal lens combo of structural/bio-mechanical problems lens becomes cloudy so less light passes to retina, focus becomes patchy

Question 31

astigmatism

Answer 31

refractive errors/shaping of the cornea contacts/glasses bens light correctly

Question 32

levator palpebrae superioris

Answer 32

lifts upper eyelid CNIII

Question 33

orbibularis oris

Answer 33

sphinctor muscle, closes eyelid, CN VII can help focus - squinting: pressure on anterior aspect of eye = lens gets more fat and image is a bit more focused

Question 34

introrbital fat

Answer 34

posterior portion of eye if malnourished - fat goes away and eyes are sunken

Question 35

lateral rectus

Answer 35

VI, lateral/abduction of the eye

Question 36

medial rectus

Answer 36

III, medial/adduction of the eye

Question 37

superior rectus

Answer 37

III, elevate the eye

Question 38

inferior rectus

Answer 38

III, depress the eye

Question 39

superior oblique

Answer 39

IV, depress/abduct the eye, superolateral aspect, goes through a pully called the trochlea

Question 40

inferior oblique

Answer 40

III, elevate/abduct the eye

Question 41

palpebrae

Answer 41

superioris & inferioris (eyelids) tarsal plate found within it lined with epithelium & hair innervated by V1&2

Question 42

canthi

Answer 42

medial (w/caruncle) & lateral caruncle is the remnant of 3rd eyelid

Question 43

conjunctiva

Answer 43

produces own tears & mucous single layer of skin that covers anterior surface of eye and fused with corneal epithelium innervated by V1 tear secretion: parasym motor - VII two types 1. palpebral - inside palpebrae 2. bulbar - on sclera conjunctivitis - pink eye conjunctival hemorrhage - ruptured BVs sclera conjunctivitis - hangover

Question 44

lac gland

Answer 44

superolateral corner of orbit secretes tears that bathe conjunctiva & corner

Question 45

lac apparatus

Answer 45

tears are squeezed into medial canthus drain through lac puncta into canaliculi lac sac - nasolacrimal duct - inferior nasal meatus