Exam 4 Special Sense Organs Flashcards
What is the eye derived from
Ectoderm
Neuroectoderm of the forebrain forms what?
Retina and pigmented structures
Surface ectoderm of the eye forms what
Lens and cornea
What forms from neural crest mesenchyme
Fibrous coats (sclera)
What are the 3 coats/tunics of the eye
Fibrous (outermost), vascular, and nervous tunic(retina)
If pressure inside the eye increases what happens to the sclera
It will not bulge, it maintains shape
What structures pass through the tiny openings in the sclera
Neurons and blood vessels
What attach directly to the sclera
Extraocular muscles
What is significant about the anterior portion of the sclera
It transitions to the cornea at the limbus and is lined with conjuctiva
What is the transition between the sclera and the cornea
At the limbus
What is significant about the posterior portion of the sclera
It is continuous with the fibrous sheath that covers CN II, contains subarachnoid space filled with CSF
What part of the fibrous tunic is the cornea
The anterior portion
What is the important function of they cornea
It is the primary refractory part of the eyeball
Which part of the cornea is convex
To the anterior
What are the 5 layers of the cornea from anterior to posterior
Corneal epithelium, anterior limiting lamina, substantia propria, posterior limiting lamina, endothelium
What is the corneal epithelium continuous with
The conjunctiva
What is the largest part (layer) of the cornea
Substantia propria
The endothelium of the cornea is the most internal layer and has what purpose
Covers inside surface of the cornea and lines the iridocorneal layer
What 3 structures are a part of the vascular tunic
Choroid, ciliary body, and iris
The blood vessels of the choroid are heavily supplied by what
Autonomic, vasomotor fibers that may have a cooling effect
How is the choroid attached to the sclera
Loosely except where the optic nerve penetrates, here it is firmly attached to the sclera
What is the pigment of the choroid
Darkly pigmented to limit passage of light from sclera to retina and vice versa
Where is the ciliary body located in relation to the choroid and iris
Continuous with the choroid to the posterior and the iris to the anterior
What is the purpose of the ciliary body
It suspends the lens and produces the aqueous fluid found in the anterior segment of the eye, some GAGS of the vitrous body
What does the ciliary body contain
The ciliary muscle - contraction of the muscle allows the lens to become more convex allowing near vision
What does the iris divide
The anterior segment into anterior and posterior chambers
What is the iris composed of muscle-wise
Consists of two muscles that control the size of the pupil
Sphincter pupillae contains what
Fibers arranged circumferentially that constrict the pupil
What is the spincter pupillae innervated by
Parasympathetic fibers (CN 3)
What does the dilator pupillae will cause what
Causes the pupil to become larger when it contracts
What is the dilator pupillae innervated by
Sympathetic fibers - radially oriented
What is the nervous tunic an outgrowth of
Outgrowth of diencephalon and can be considered to be a specialized portion of the brain
What is the nervous tunic in contact with
The choroid externally and the vitreous body internally
What are the ten layers of the retina
Pigmented layer (cementing layer), rods/cones, external limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, nerve fiber layer, internal limiting membrane
What do rods and cones synapse with
Inner nuclear layer cells
Bipolar cells relay information to
The ganglion layer cells
Multipolar cells carry info to where
The lateral geniculate body
What do axons from the lateral geniculate body form
The optic radiation
The axons forming optic radiation synapse where
Brodmann area 17 of the occipital lobe
What structures are visible upon funduscopic exam
Optic disc and macula lutea
Where is the optic disc
Point at which the optic nerve attaches to the eyeball
Does the optic disc contain photoreceptors
Nope
What enters the eye at the optic disc
Major blood vessels
Where is the macula lutea
The darker area in the center of the fundus
What is in the middle of the maculae lutea
The fovea centralis
Where is the area of the clearest vision
The macula lutea
What type of photoreceptor is found in the macula lutea
Cones
What is aqueous humor
Clear fluid found on the posterior aspect of the ciliary body
What secretes the aqueous humor
The ciliary processes
Where is the aqueous humor secreted into
The posterior chamber; part of the anterior segment located posterior to the iris
Where does the aqueous humor leave the eyeall
Through the scleral venous sinus
What causes glaucoma
Increased pressure within the anterior segment of the eyeball - can result in blindness
How does the lens allow for near vision
Increasing the convexity
Is the lens vascular?
No
What separates the anterior and posterior segments
The lens
What is presbyopia
Lens gents harder with age resulting in more difficult near vision
What are cataracts
Lens becomes less and less transparent
What fills the posterior segment
Vitreous body
What are characteristics of the vitreous body
Gelatinous and transparent
What is the hyaloid canal
A vestigial structure connecting the optic nerve and posterior aspect of the lens.
What did the hyaloid canal contain
Contained the fetal hyaloid artery and serves no functional purpose in the adult
Where are lacrimal glands located
Superolaterally to the eyeball
What do lacrimal glands do
Secrete tears that are carried to the surface of the eye by excretory ducts
Where are lacrimal ducts found
In each eyelid below and medial to the eyeball
What do lacrimal ducts do
Drain tears into the lacrimal sac
Where is the lacrimal sac found
Found in a groove between the lacrimal bone and the maxilla, the most superior part of the nasolacrimal duct
What does the nasolacrimal duct do
Drain tears from the lacrimal sac into the inferior nasal meatus
What are tarsal glands
Modified sebacceous glands in each eyelid
What do tarsal glands do
Secrete oily substance that covers tears upon binking reducing evaporation
All arteries to the eyeball are branches of the _____
Ophthalmic artery
What artery runs between the sclera and choroid
The long posterior ciliary artery (medial and lateral)
How many short ciliary arteries enter the eyeball
6-12
Where do the short ciliary arteries enter the eyeball
On the posterior surface forming a ring around the optic nerve
How are the anterior ciliar arteries spread
3-4 over and 3-4 under the eyeball (total = 6-8)
How does the central retinal artery travel
Via the optic nerve to retina where it spreads out into an extensive network
What is special about the central retinal artery
It is the only artery that supplies the retina
How do viens travel
With their respective arteries
What is the nerve supply to the eyeball
Branches of the nasociliary nerve of the ophthalmic division of the trigeminal nerve
What do long ciliary nerve supply
Sensory for the ciliary body, iris, and cornea
What are the sensory nerves for the eyeball
Short ciliary nerves
What do postganglionic sympathetic fibers extend from
The cavernous plexus passing through the ciliary ganglion
What do postgang symp fibers go to
Reach the ciliaris and dilator pupillae muscles
Where do postganglionic parasympathetic fibers extend from
The ciliary ganglion
What do postgang parasymp supply
Ciliaris and sphincter pupillae muscles
