Anatomy-The Orbit Flashcards
In the orbit, the medial walls are (blank) to each other and the lateral walls are (blank) to each other
parallel
orthogonal
What is the outpocketing of the forebrain that induces a thickening of the surface ectoderm which will form the lens placode or vesicle?
diencephalic part
What do we consider CN 1 and CN2?
not true cranial nerves
Where do columns stop?
in the midbrain, therefore there are no columns in the forebrain
What is the cornea formed by?
the surface ectoderm
What does the visual retina do?
absorbs light and reduces the amount of bounding around of light
What does the diencephalon form first before forming all the layers of the retina as well as the retinal pigment epithelium and parts of the iris and ciliary body?
the optic cup
What does the optic cup form?
all the layers of the retina as well as the RPE and parts of the iris and ciliary body
What is the muscle of the ciliary body formed by?
mesenchyme that invades the optic cup
What all does the mesenchyme of the eye form?
ciliary muscles, sclera and choroid
The (blank) is the white of the eye, is the opaque, fibrous, protective, outer layer of the eye containing collagen and elastic fiber
sclera
The (blank) is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera.
choroid
When the dura reaches the back of the orbit it separates into 2 layers; what are they?
meningeal and periosteal
Which layer of the dura goes to the undersurface of the bone of the top of the orbit?
periosteal
What happens to the meningeal layer of the dura when it reaches the orbit?
it follows the optic nerve and then is continuous with the sclera
Where does the cornea come from?
surface ectoderm and underlying infiltrating mesenchyme
Lens arises from the (blank)
lens placode
What all does the optic cup give rise to?
most of the eye, retina, iris
(blank) invading the area of the optic cup forms smooth muscle, sclera and choroid.
mesenchyme
Cornea comes from (blank)
surface ectoderm
Most severe eye defects are associated with malformation of the (blank)
brain or cranial cavity
cyclopia,anopthalmia
(blank) is a relatively common defect associated with incomplete closure of the choroid fissure, a groove that develops for the invaginating hyaloid artery which later regresses and only remains in the optic nerve as the central artery.
Colomboma
What is the hyaloid artery and what happens to it?
it runs from within the optic nerve to the lens to provide nutrition to the lens in the fetus, but regresses before birth to form the central artery of the optic nerve.
What does the hyaloid artery run through?
The choroid fissure. This is what will remain in colomboma because it fails to close resulting in an abnormality.
Each orbit has what kind of shape?
pyramidal shape
Where is the orbital margin?
Where is the apex of the orbit?
at the base
the optic canal
THe medial walls of the orbit are parallel while the lateral walls of the orbit are at right angles to each other, what does this mean?
this means that the your orbits are facing at angles while your globe is facing straight ahead which means that your optic nerve will be entering medially in your orbit and the fovea will be more lateral
Most of the muscles to the eyeball, will arise from where and attach where and what does this mean?
the back of the orbit, and attach medially. They will be adductors!
What are the bones of the orbit?
frontal zygomatic maxillary lacrimal ethmoid sphenoid palatine
What are the foramen of the sphenoid bone?
optic canal, superior orbital fissure, inferior orbital fissure, foramen ovale, foramen spinosum
Where does the infraorbital nerve lie? How can you easily damage this nerve?
just above the maxillary sinus where it leaves through the infraorbital foramen
blowout fracture
where in your orbit is the lacrimal sac?
Where is the lacrimal gland?
medial
lateral
What are the three layers to the eyeball?
Outer
middle
inner
What makes up the outer layer of the eyeball?
the sclera (opaque) and cornea (translucent)
What makes up the middle layer of the eyeball?
Choroid
ciliary body
Iris
(pigmented layer)
What makes up the inner layer of the eyeball?
retina
has visual and non-visual parts
What kind of epithelium makes up the visual layer of the retina?
Retinal pigment epithelium (RPE)
and non-visual parts
The visual layer of the retina will have what special things?
rods and cones
What are cones for and where do you mostly find them?
high visual acuity; midline of the back of your eye
What are rods for?
night vision and large visual fields
The anterior and posterior chamber of the eye are separated by the (blank)
iris
What suspends the lens in place?
the zonular fibers
What is the vitreous humor/body made up of?
99% water (has hyaloid canal within it)
What is the optic disc?
entry of optic nerve with central retinal vessels
Where do you get a blind spot in your eye?
at the optic disc
Where do you find the largest concentration of cone cells?
the fovea
What is the macula with fovea centralis for?
acute vision
Where do you find the anterior chamber?
in front of the iris
Where do you find the posterior chamber?
behind the iris
What is the vitrous chamber?
large cavity in the eye behind the lens and in front of the retina
Is there a subarachnoid space in the eye and if so, where does it go?
yes, it goes all the way up to the optic disc
What will happen if you have CNS pressure building up behind the eye?
you will get a ring around the optic disc
Where do you find ganglion cells in the eye?
visual layer
How many layers of cells are associated with the retina and what are of significant importance for sending messages to the optic nerve?
about 10
ganglion cells
What happens to the axons of the ganglion cells of the eye?
they will pass over the visual layer and accumulate at the optic disc and enter the optic nerve
Why is the retina less able to pick up light except in the area of the fovea centralis (macula)?
because optic ganglion cells block the ability of the retina to take in light except at the fovea where they are not present
Light rays will focus on the macula, depending on where light is coming from, you will have to change the refractive powers of your eye to get it there. How do you do this?
Shape of cornea (isnt really alterable)
roudness of lens (alterable)
air/water interface (most powerful refractive changer)
What is the natural shape of your lens if you pop it out?
rounded
What is the natural shape of your lens in your eyesocket?
flat because zonal fibers are tightened and holding the lens taught by attached to the ciliary muscle.
What is a flat lens useful for?
far vision
What is a round lens useful for?
up close vision
What is up with nearsightedness?
your pole length is too long for the refractive index
Where does aqueous humor come from and how does it flow?
it comes from the ciliary process to the scleral venous sinus (schlemms canal)
What does the iris do?
pigmented layer, sphincter of pupil, dilator of pupil
What is glaucoma?
increased intraocular pressure (greater than 20-22 mm)
There is a substance in the anterior and posterior chambers called aqueous humor (as opposed to the vitrious humor in the vitrous chamber) this is created by the (blank), then it flows into the ciliary chamber into the posterior chamber over the lens and into the anterior chamber where it is absorbed by the sclerol venous sinus (schlemms canal). Failure to absorb or over production will elevate the pressure of aqueous humor in these chambers. AND cause??????
ciliary process
glaucoma
What are the 2 layers of the iris?
the pigmented layer and the muscle layer
What are the 2 muscles of the iris, how are the fibers arranged, and what are they innervated by?
the sphincter papillae muscles which is circularly arranged (parasympathetics)
the dilator which is radially arranged (sympathetics)
In the eye, which happen faster, parasympathetics or sympathetics?
parasympathetics
cuz you dont want to dilate your eyes quickly or you could blind yourself
The (blank) muscle is a ring of smooth muscle in the eye’s middle layer (vascular layer) that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm’s canal.
ciliary
What is ciliary muscle innervated by and how are its fibers oriented?
parasympathetics
circularly (most medial)
radially (most lateral)
How does the ciliary muscle change the shape of the lens?
by reducing the tension of the zonal fibers that support the lens. The circular fibers will contract like a sphincter and reduce the tension on the zonal fibers and the radial fibers will reduce the cross sectional diameter by pulling the whole process towards the sclerocorneal junction which will move the lens forward and thus round up the lens
What meningeal layers cover the optic nerve?
pia mater, arachnoid, and meningeal dura
The deep fascia from the muscles of the superior eyelid form the (blank) which comes off onto the sclero of the eyeball.
bulbar sheath
What muscle goes to the tarsal plates in the superior eyelid?
the levator palpebrae muscle
What is the little tiny layer of muscles that comes from levator palpebrae and attaches to the tarsal plate (helps raise eyelid)? What is this muscle made out of?
Superior tarsal muscle (mueller muscle)
smooth muscle
What basically makes up the eye socket?
the bulbar sheath
What besides the optic nerve comes out of the optic disc?
central artery of retina
The inferior rectus and the inferior oblique make up what ligament?
the suspensory ligament
What is the optic nerve surrounded by? What does increased intracranial pressure show up as around the disc? What do you call this?
CSF, arachnoid, dura
swelling around disc
papilledema (venous congestion, raised disc)
Can you see papilledema unilaterally?
yes, it usually occurs bilaterally but can occur unilaterally in cases of tumor.
Which vessels to you visualize with opthalmoscope?
ciliary vessels
central artery