Final Exam: Unit VIII: Special Sense Organs-- Eyes Flashcards
What are the special sense organs of vision?
the eyes
What are the eyes derived from?
Ectoderm:
- Neuroectoderm of forebrain
- Surface ectoderm
- Neural crest mesenchyme
What part of the eye is derived from neuroectoderm of the forebrain?
- retina
- pigmented structures
What part of the eye is derived from surface ectoderm?
- lens
- cornea
What part of the eye is derived from Neural crest mesenchyme?
- fibrous coats (sclera)
What are the three coats or tunics the eye is composed of?
- Fibrous Tunic (outermost)
- Vascular Tunic
- Nervous tunic or retina
What structures does the Fibrous tunic of the eye contain?
- Sclera
2. Cornea
What is the white part of the eye called? Describe its make-up.
sclera –> is thick, dense, firm**, and opaque
What maintains the shape if the pressure inside the eye increases?
the sclera–> it is thick, dense, and firm
Does the sclera have tiny openings? Why or why not?
yes, many–> to allow structures to pass through like blood vessels and neurons
Where do extraocular eye muscles attach to on the eye?
to the sclera
What is the transition of the sclera into the cornea called?
limbus
What is the sclera continuous with posteriorly?
with fibrous sheath that covers CN II (optic nerve)
What makes up the anterior part of the Fibrous Tunic of the eye? Describe its make-up.
cornea–> clear and transparent
What is the primary refractory part of the eyeball?
cornea
- first part of eye light must pass through
- most responsible for focusing light on the retina
What is the sclera lined with anteriorly?
conjunctiva (mucous membrane on inside of eyelid)
What is an irregularity in the cornea called?
an Astigmatism
Which way is the cornea convex, anteriorly or posteriorly?
anteriorly
How many layers does the cornea consists of? Name them from anterior to posterior.
Five:
- Corneal Epithelium (most external)
- Anterior limiting lamina
- Substantia propria
- Posterior limiting lamina
- Endothelium (most internal)
Where are most vision problems associated with farsightedness and far nearsightedness due to?
the cornea not focusing light on the retina properly
What is the most external layer of the cornea? What is it continuous with?
Corneal epithelium; continuous with conjunctiva
What is the thickest layer of the cornea?
Substantia propria (is largest and thickest part of cornea)
What is the most internal layer of the cornea? What does it line?
Endothelium; lines the iridocorneal layer
What does the Vascular Tunic of the eye consists of?
- Choroid
- Ciliary body
- Iris
What is the thin part of the vascular tunic that has rich blood supply and its blood vessels are heavily supplied by autonomic vasomotor fibers?
Choroid
–autonomic vasomotor fibers–> may have a cooling effect
Is the Choroid loosely or firmly attached to the sclera?
Loosly attached; EXCEPT where optic nerve penetrates sclera–> there the choroid is firmly attached to the sclera
Is the Choroid lightly or darkly pigmented? Why?
darkly pigmented–> helps limit passage of light both through sclera to retina and through retina to sclera
What is the Ciliary body (in Vascular tunic) continuous with to the posterior? what about anteriorly?
posteriorly-> with choroid
anteriorly–> with iris
What suspends the lens?
ciliary body
What does the ciliary body produce? What segment of the eye is this found in?
produces aqueous fluid–> found in anterior segment of the eye
may also produce–> some GAGs of the vitrous body
What muscle does the ciliary body contain? What does contraction of this muscle do?
ciliary muscle–> contraction allows lens to become more convex–> allowing for near vision
What is the colored part of the eye? What tunic is it in?
iris–> ranges from light blue to dark brown
Vascular tunic
What does the iris divide the eye into?
the anterior segment into anterior and posterior chambers
How many muscles does the iris consist of? What do they control?
Two:
- Sphincter pupillae
- Dilator pupillae
- -> control size of pupil
What type of fiber arrangement does the Sphincter pupillae contain? What effect do they have on the pupil? What type of fibers innervate it?
(part of iris)
circumferentially arranged fibers–> constrict the pupil
parasympathetic fibers innervate it
What type of fiber arrangement does the Dilator Pupillae consists of? What effect do they have on the pupil? What type of fibers innervate it?
radially oriented fibers–> dilates pupil/becomes larger when they contract
sympathetic fibers innervate it
What is the Nervous tunic or called retina an outgrowth of?
the Diencephalon–> therefore can be considered to be a specialized portion of the brain
(retina = only time can “see” CNS of someone)
What is the Nervous tunic/Retina in contract with externally? What about internally?
Externally–> thin layer in contact with choroid
Internally–> vitreous body
How many layers does the Retina consists of? What are they from external to internal?
Ten:
- Pigmented layer (cementing layer)
- Rods and cones (photoreceptors)
- External limiting membrane
- Outer nuclear layer
- Outer plexiform layer
- inner nuclear layer (cell bodies of bipolar cells)
- inner plexiform layer
- ganglion cell layer (contain ganglion cell bodies)
- nerve fiber layer
- internal limiting membrane
What are the five cells involved in the vision pathway?
- photoreceptors – rods and cones
- inner nuclear layer cells– bipolar cells
- ganglionic layer cells – multipolar cells
- Lateral Geniculate Body (LGB)– axons form the optic radiation
- Brodmann area 17 of occipital lobe
What retinal structures are visible upon a funduscopic exam?
- optic disc
2. Macula lutea
What is the point at which the optic nerve (CN II) reaches the eyeball?
Optic disc
What color does the Optic disc appear?
white or yellowish
Are there any photoreceptors in the optic disc? Why?
no–> major blood vessels enter/exit eyeball here
What is the darker area in the center of the fundus of the eye?
Macula lutea
What is in the middle of the Maculae lutea?
Fovea centralis
What is the area of clearest vision?
Maculae lutea
Are there photoreceptors in the Maculae lutea? What kinds?
yes, only cones
What is the loss of cone cells in the Macula Lutea and results in vision loss?
Macula degeneration
What are the four refractory components of the eyeball?
- Cornea
- Aqueous humor
- Lens
- Vitreous body
What is the most anterior and the primary refractory structure of the eye?
Cornea
What is clear fluid secreted by the ciliary processes? Where is this found?
aqueous humor; found on posterior aspect of ciliary body and is secreted into posterior chamber (part of anterior segment–located posterior to iris)
How does the aqueous humor travel that is secreted by the posterior aspect of the ciliary body?
secreted into posterior chamber–> passes through pupil into anterior chamber–> travels laterally—> leaves eyeball through scleral venous sinus (Canal of Schlemm)
How does Glaucoma result?
from increased pressure w/in anterior segment of eyeball–> blindness can result
Describe the make-up of the Lens.
transparent, biconvex, avascular
T/F. The lens of the eye is very vascular.
False–it is avascular
Does increasing or decreasing the convexity of the lens allow for near vision?
increasing the convexity
What does the lens separate in the eye?
the anterior segment from the posterior segment
What is it called when the lens gets harder with age, resulting in more difficult near vision?
Presbyopia (harder to increase convexity of lens, lens is losing its resiliency)
“arms too short to read”
What is it called when the lens becomes less and less transparent?
Cataracts (loss of transparency
Tx: by taking a few layers off of the lens surgically)
What does the Vitreous body fill in the eye? Describe its make-up.
fills posterior segment (area behind lens)
gelatinous and transparent
What is the vestigial structure that connects the optic nerve and posterior aspect of the lens called?
Hyaloid canal
serves no functional purpose in the adult
What did the Hyaloid canal used to contain in the fetus?
contained the fetal hyaloid artery–> and serves no functional purpose in the adult
What are the Extraocular msucles of the eye?
- Superior rectus
- Inferior rectus
- Medial rectus
- Lateral rectus
- Superior oblique
- Inferior oblique
What are the three accessory structures of the eye?
- Extraocular muscles (6)
- Lacrimal apparatus
- Tarsal glands
Where are the lacrimal glands located? What do they secrete? Where is this secretion carried?
superolaterally to the eyeball; secrete tears –> carried to surface of eye by excretory ducts
Where are lacrimal ducts found in the eye? What is their function?
each eyelid below and medial to eyeball–> they drain tears into lacrimal sac
Where is the lacrimal sac found?
in a groove b/w lacrimal bone and maxilla–> is the most superior part of the nasolacrimal duct
What is the most superior part of the nasolacrimal duct?
lacrimal sac
What does the nasolacrimal drain tears from and into?
from the lacrimal sac –> into the inferior nasal meatus
why nose runs when we cry
What direction do our tears flow across our eye?
lateral –> medial
In order, list the flow of tears of the Lacrimal appparatus.
Lacrimal glands secrete tears–> carried to surface of eye via excretory ducts–> tears travel lateral to medial across eye–> lacrimal ducts drain tears into –> lacrimal sac–> which is connected to nasolacrimal duct that drains tears into–> inferior nasal meatus
In kids, what part of the Lacrimal apparatus may not be open, and create a goopy eye?
the lacrimal duct (located in eyelid below and medial to eyeball; drains tears into lacrimal sac)
Where are tarsal glands of the eye located?
in each eyelid
What type of glands are tarsal glands of the eye considered?
modified sebaceous glands–> secretes an oily substances that covers tears upon blinking
What purpose does the oily substance secreted from tarsal glands that coats tear serve?
to reduce evaporation of tears
What are all arteries to the eyeball branches of?
the ophthalmic artery
What are the four different types of arteries supplying the eye?
- Long posterior ciliary arteries (2)
- Short ciliary arteries (6-12)
- Anterior ciliary arteries (6-8)
- Central Retinal artery (1)
How many long posterior ciliary arteries supply one eye? What structures do they run b/w?
2–> one medial and one lateral–> runs b/w sclera and choroid
How many short ciliary arteries supply one eye? How do they enter the eyeball?
6-12–> enter eyeball on posterior surface piercing the sclera and forming a ring around the optic nerve
How many anterior ciliary arteries supply one eye?
6-8–> 3-4 arch over eyeball and 3-4 go under eyeball and pierce sclera on top or bottom of eye
What is the only artery to supply the retina? How does it travel?
Central Retinal Artery –> travels via the retina where it spreads out into an extensive network
What are the three ways of venous drainage of the eyeball?
- Anterior ciliary veins–> accompany ant. ciliary arteries
- Long posterior ciliary veins-> travel w/ long post. ciliary arteries
- Central retinal vein–> travels longside the central retinal artery
What is the only vein to drain the retina?
Central Retinal vein
What is the nerve supply to the eyeball from?
branches of Nasociliary Nerve of V1 division of trigeminal nerve
- Long ciliary nerves
- Short ciliary nerves
What do the Long Ciliary nerves going to the eye travel with? What are their function?
vessels of same name
sensory for:
- ciliary body
- iris
- cornea
What is the function of the Short ciliary nerves going to the eyeball?
carry sensory info for the eyeball
Where are postganglionic sympathetic fibers coming from that go to the eye?How do they reach the eyeball? What are they supplying?
come from cavernous plexus–> pass through ciliary ganglion–> reach ciliaris and dilator pupillae muscles
Where are postganglionic parasympathetic fibers coming from that go to the eye? Where are they going to?
come from the ciliary ganglion–> follow similar path to cilaris and sphincter pupillae muscles
