Unit VIII - Eye Flashcards
What structures of the eye are derived from the neuroectoderm of the forebrain?
Retina and pigmented structures
The lens and cornea are derived from what specific embryological layer?
Surface ectoderm
The fibrous coats (sclera) are derived from which specific embryological layer?
Neural crest mesenchyme
What is the term for the white part of the eye?
Sclera
What happens to the sclera if pressure inside the eye increases?
Shape is maintained due to its thick, dense, and firm structure
Does light pass through the sclera?
No, it is opaque
What things pass through the many tiny openings seen on the sclera?
Blood vessels and neurons
What attaches to the sclera?
Extraocular muscles
What is the term for the location where the sclera transitions into the cornea?
Limbus
What is the sclera continuous with posteriorly?
Fibrous sheath (made of arachnoid) that covers cranial nerve II
What lines the sclera anteriorly?
Conjunctiva
What part of the eye of transparent and clear?
Cornea
What is the primary structure of the eye used for focusing light?
Cornea
Is the cornea concave or convex anteriorly?
Convex
What layer of the cornea is continuous with the conjunctiva?
Corneal epithelium
What is the largest/thickest part of the cornea?
Substantia propria
What is the innermost layer of the cornea?
Endothelium
What does the endothelium of the retina line?
Iridocorneal layer
What are the layers of the cornea in order from outermost to innermost?
Corneal epithelium, anterior limiting lamina, substantia propria, posterior limiting lamina, endothelium
What makes up the fibrous tunic of the eye?
Sclera and cornea
What makes up the vascular tunic of the eye?
Choroid, ciliary body, and iris
Which tunic of the eye is the only complete layer?
Fibrous tunic (makes it all the way around the eye)
Which tunic of the eye has many blood vessels and lots of autonomic influence (especially sympathetic)?
Vascular tunic
What special effect may be possessed by the blood vessels that supply the vascular tunic of the eye?
Cooling effect
Where is the only location where the choroid is anchored to the sclera?
Where the optic nerve penetrates it
What is the choroid loosely attached to?
Sclera
What is the purpose of the dark pigment of the choroid?
Helps limit passage of light both through sclera to retina and through retina to sclera
What is the ciliary body continuous with?
Choroid (posteriorly)
Iris (anteriorly)
What structure is suspended by the ciliary body?
Lens
What is the substance produced by the ciliary body that is found in the anterior segment of the eye?
Aqueous fluid
What divides the eye into general anterior and posterior segments?
Lens
What divides the anterior segment of the eye into anterior and posterior chambers?
Iris
What else can the ciliary body produce besides the aqueous fluid seen in the anterior segment of the eye?
Glycosaminoglycans of the vitreous body
What contains the ciliary muscle?
Ciliary body
What is the action of the ciliary muscle?
Contraction makes lens more convex to allow for nearer vision
What is the colored part of the eye?
Iris
What is the range of colors seen of the iris?
Light blue to dark brown
What two muscles make up the iris?
Sphincter pupillae and dilator pupillae
Which muscle of the iris contains fibers that are circumferentially oriented to constrict the pupil?
Sphincter pupillae
What part of the autonomic nervous system innervates the sphincter pupillae muscle?
Parasympathetic fibers
Which muscle of the iris has radially arranged fibers that cause the pupil to enlarge when contracted?
Dilator pupillae
The eye is derived from what embryological layer?
Ectoderm
What is another name for the retina?
Nervous tunic
What does the retina contact externally?
Choroid
What does the retina contact internally?
Vitreous body
How many layers of the retina are there?
10
What is another term for the pigmented layer of the retina?
Cementing layer
What layer of the retina is involved in a detached retina?
Cementing layer (pigmented layer)
What kinds of cells are found in the inner nuclear layer?
Bipolar cells
What kinds of cells are found in the nerve fiber layer?
Ganglion cell axons
What are the five cells involved in the vision pathway?
Photoreceptors –> inner nuclear layer (bipolar) cells –> ganglionic layer cells –> lateral geniculate body –> Brodmann area 17
What area of the eye is involved with the blind spot?
Optic disc
What is the point at which the optic nerve attaches to the eyeball?
Optic disc
To which side does the optic disc deviate?
Nasal side
What color does the optic disc appear?
White or yellowish
Are photoreceptors present in the optic disc?
No; no vision occurs here
Where do major blood vessels enter the eyeball?
Optic disc
What is located at the very center of the eye?
Macula lutea
The macula lutea is the darker area in the center of what structure?
Fundus
What is located in the middle of the maculae lutea?
Fovea centralis
What is the area of clearest vision?
Macula lutea
What are the only photoreceptors found in the macula lutea?
Cones
As we head toward the periphery, we see more of which photoreceptor?
More rods, less cones
What kind of photoreceptors do we see on the very edges of our field of vision?
Rods only
What is the most anterior primary refractory structure?
Cornea
What is the condition of abnormality in the shape of the cornea?
Astigmatism
What is the clear fluid secreted by the ciliary processes found on the posterior aspect of the ciliary body?
Aqueous fluid
Aqueous fluid is secreted into which chamber of the eye?
Posterior chamber (part of the anterior segment located posterior to the iris)
The aqueous humor passes through the pupil into the anterior chamber, travels laterally, and leaves the eyeball through what sinus?
Scleral venous sinus
Canal of Schlem
What causes glaucoma?
Increased pressure within the anterior segment of the eyeball (can result in blindness)
What is unique about the vascular supply to the lens?
AVASCULAR
Is the lens convex or concave?
Biconvex
Does increasing convexity or increasing concavity of the lens allow for nearer vision?
Increasing convexity
What structure separates the anterior segment from the posterior segment?
Lens
Which segment of the eye is filled with aqueous humor?
Anterior
Which segment of the eye is filled with vitreous humor?
Posterior segment
What condition results when the lens gets harder with age and loses its flexibility which can result in more difficult near vision?
Presbyopia
What condition results from the lens becoming less transparent?
Cataracts
What are the characteristics of the vitreous humor?
Gelatinous and transparent
What is the vestigial structure connecting the optic nerve and the posterior aspect of the lens?
Hyaloid canal
What artery is contained in the hyaloid canal?
Fetal hyaloid artery
In what population does the hyaloid canal serve no functional purpose?
Adults
In which direction do tears flow?
Lateral to medial
Where are the lacrimal glands located?
Superolaterally to the eyeball
What structures carry tears from the lacrimal glands to the surface of the eye?
Excretory ducts
Where are the lacrimal ducts found?
In each eyelid below and medial to the eyeball
What is the function of the lacrimal ducts?
Drain tears into the lacrimal sac
Where is the lacrimal sac found?
In a groove between the lacrimal bone and the maxilla
What is the most superior part of the nasolacrimal duct?
Lacrimal sac
What structure drains tears from the lacrimal sac into the inferior nasal meatus?
Nasolacrimal duct
Where are the tarsal glands located?
In each eyelid
What kind of glands are tarsal glands?
Modified sebaceous glands
What do tarsal glands secrete?
An oily substance that covers tears upon blinking
All arteries to the eyeball are branches of what artery?
Ophthalmic artery
How many long posterior ciliary arteries are there?
1 on each side (medial and lateral)
The long posterior ciliary arteries run between what structures?
Sclera and choroid
Which arteries of the eye enter the eyeball on the posterior surface forming a ring around the optic nerve, and how many are there?
Short ciliary arteries (6-12)
Which arteries of the eye arch either over or under the eyeball, and how many are there?
Anterior ciliary arteries (6-8 total)
What artery is the only artery that supplies the retina?
Central retinal artery
The central retinal artery travels to the retina via what structure?
Optic nerve
How are the veins involved in the drainage of the eye named?
For the arteries they accompany
What part of the trigeminal nerve makes up the nerve supply to the eyeball?
Branches of the nasociliary nerve of the ophthalmic division of the trigeminal nerve
What nerves of the eyeball are sensory for the ciliary body, iris, and cornea?
Long ciliary nerves
What nerves are sensory for everything besides the ciliary body, iris, and cornea?
Short ciliary nerves
Postganglionic sympathetic fibers reach which eye muscles?
Ciliaris and dilator pupillae muscles
Postganglionic sympathetic fibers come from what plexus and through what ganglion to reach the ciliaris and dilator pupillae muscles?
Cavernous plexus to the ciliary ganglion
Postganglionic parasympathetic fibers reach what muscles of the eye?
Ciliaris and sphincter pupillae muscles
Postganglionic parasympathetic fibers travel from what ganglion to reach the ciliaris and sphincter pupillae muscles?
Ciliary ganglion
