Vision, Hearing, and Vestibulation Flashcards
Cornea
the transparent surface of the eye that bends (refracts) the light and focuses it on the back of the eye.
Sclera
outer fibrous, white layer of the eyeball.
The sclera and the cornea are continuous with each other but have different structures and functions.
Lens
changes shape to be able to focus light on the back of the eye regardless of the distance of the object
Pupil
opening in the center of the iris through which light enters the eye.
Iris
- surrounds the pupil and contains smooth muscle to dilate or constrict the pupil.
- this is deep to the cornea
- It contains a pigmented layer that gives our eyes their color.
Vitreous humor
a jelly-like substance that fills the chamber of the eye posterior to the lens and gives the eye its shape. It transmits light to the retina.
Choroid
the middle vascular layer in the wall of the eye
highly vascular, darkly pigmented membrane that nourishes the retina.
Retina
this is the inner layer of the eye
- this has two layers, the pigmented layer and the neural layer
the neural layer of the eye, which contains the photoreceptors for vision
where do the extraocular muscles originate
All but the inferior oblique muscle originate in a common tendinous ring at the posterior aspect of the orbit
Lateral rectus
Moves eye laterally (abducts)
innervation: CN VI abducens nerve
location: this is on the lateral side of each eye and has straight fibers that when constricted cause the eye to abduct
medial rectus
Moves the eye medially (adducts)
innervation: CN III Oculomotor nerve
location: this is on the medial side of each eye and has straight fibers that when constricted cause the eye to adduct
Superior rectus
Elevates the eye (look up)
innervation: CN III Oculomotor Nerve
location :this is on the superior side of each eye and has straight fibers that when constricted cause the eye to look upward
Inferior rectus
Depresses the eye (look down)
innervation: CN III Oculomotor Nerve
location :this is on the inferior side of each eye and has straight fibers that when constricted cause the eye to look downward
inferior oblique
Elevates eye and turns it laterally
innervation: CN III Oculomotor Nerve
location : this is inserting inferiolateral side of each eye and has curving fibers that when constricted cause the eye to look upward and outward
this is the only extrinsic muscle that doesn’t originate at the common tendinous ring (originates at the inferior medial corner of the eye
superior oblique
Depresses eye and turns it laterally
innervation: CN IV Trochlear Nerve
location: this is on the superior portion of the eye and when the muscle constricts it causes the eye to look downward and outward
optic nerve
travels posteriorly from the eye.
The optic nerves come together at the optic chiasm.
After the optic chiasm, these axons continue as the optic tract until the majority of them synapse in a nucleus of the thalamus.
optic chiasm
- this is where the optic nerves meet
- this is where the nasal retina fibers cross and enter the optic tract to travel with the opposite temporal retina fibers
common tendinous ring
this is at the posterior orbit and it is where the the four rectus muscles and the superior oblique muscle originates
lacrimal sac
this is where tears collect
optic tract
- these carry information from both eyes, both retinas, but one visual field
- this carries the information from the optic chiasm to the lateral geniculate nucleus
ciliary body
this is a thickened portion of the choroid that encircles the lens of the eye
ciliary muscles
- this is a muscular ring projecting into the interior of the eye
- this can apply or take away tension on the ciliary processes and this changed the amount that the ligaments pull on the lens, which allows for a change in the shape of the lens
suspensory ligaments
- also called ciliary zonule
- these run from the ciliary process to the lens and they create a circle around the lens
- the lens is essentially suspended by these ligaments
optic disc
this is where the axons of the ganglion cells converge
- this is a circular region just medial to the fovea centralis on the posterior aspect of the eye
- this is the origin of the optic nerve
- no photoreceptors are on the optic disc
- this creates the blind spot because light striking the area goes unnoticed since there are no photoreceptors
- involuntary eye movements fill in the missing information