Orbit Flashcards
What bones make up the outer rim of the orbit?
Frontal, zygomatic, and maxilla bones
What bones make up the inner part of the orbit?
Sphenoid (greater & lesser wings), ethmoid, lacrimal, and palatine bones
What bones makeup the floor of the orbit?
Maxilla, zygomatic, palatine bones
What bones makeup the roof of the orbit?
Frontal, sphenoid bones
What bones makeup the medial wall of the orbit?
Ethmoid, lacrimal, frontal, maxillary, palatine bones
What bones makeup the lateral wall of the orbit?
Zygomatic, sphenoid, frontal, maxilla bones
What lies at the apex of the orbit?
Optic canal
What makes up the base of the orbit?
Orbital margin
What is the axis of the orbit?
45 degrees from sagittal
What is the name for the space b/w the upper and lower eyelids?
Pelpebral fissure, bound by the upper and lower palpebral margins (palpebrae = eyelids)
The upper and lower palpabral margins meet at the ___________.
Canthus (medial and lateral canthi)
How many layers does a palpebra have associated w/it?
7
What is the major m. of the eyelid?
Levator palpabrae superioris m.
What is the lacrimal lake?
The larger medial angle of the eyelid
What is the fleshy elevation seen in the medial eye (next to the lake)?
What’s contained in it?
- Lacrimal caruncle
- Sweat glands, sebaceous glands, cilia
What is the name of the CT band found just lateral to the lacrimal caruncle?
Plica semilunaris (separates sclera from lacrimal lake)
Where are lacrimal glands located?
What do the ducts of the lacrimal gland drain directly into?
- Superolateral aspect of eye
- Superior palpebral fornix (of upper lid. aided by blinking)
What is the function of the puncta lacrimali?
Where are they located?
- Drain opening for the tears
- Medial side of upper and lower lid
What is the function of the lacrimal canaliculus?
Where are they located?
- It’s a duct from the puncta lacrimali to the lacrimal sac
- Upper and lower palpebrae
What is the lacrimal sac?
Where is it located?
- Collection of fluids
- Fossa of lacrimal bone
Where does the nasolacrimal duct drain?
Nasal sinus
What do the recti mm. originate?
Anulus tendineus (fibrous ring encircling inf and sup orbital fissures + optic canal) - Placed medially, so mm. travel laterally and anteriorly to reach eye
Where does the superior oblique m. originate?
Sphenoid
Where does the inferior oblique m. originate?
Maxilla
Where does the levator palpebrae superioris m. originate?
Sphenoid
What are the vertical axis actions of each of the 6 eye mm.?
Medial rectus: none Lateral rectus: none Superior rectus: elevates Inferior rectus: depresses Superior oblique: depresses Inferior oblique: elevates
What are the horizontal axis actions of each of the 6 eye mm.?
Medial rectus: adducts Lateral rectus: abducts Superior rectus: adducts Inferior rectus: adducts Superior oblique: abducts Inferior oblique: abducts
What does the superior division of the oculomotor n. innervate?
Superior rectus and levator palpebrae superioris mm.
What does the inferior division of the oculomotor n. innervate?
Medial and inferior recti, inferior oblique mm.
Besides the optic n., what travels through the optic canal?
Ophthalmic a.
What are the 3 primary branches that V1 divides into?
“NFL”
- Nasociliary n.
- Frontal n.–> Supratrochlear and supraorbital nn.
- Lacrimal n.
What is the pw of the nasociliary n. across the eye? What branches does it give off (just kind of know them)
- Lateral to medial
- Short ciliary nn., long ciliary nn., posterior ethmoidal n., anterior ethmoidal n., infratrochlear n.
How does the communicating branch of the ciliary ganglion reach the eye?
Runs thru the ciliary ganglion w/o synapsing, then reaches eye by running w/short ciliary nn.
What are the only types of fibers that synapse w/ciliary ganglion?
What other fibers run directly thru it?
- Parasymp fibers from CN III
- Sensory and symp fibers
What m. causes constriction of the pupil via parasympathetic stimulation?
Sphincter pupillae m.
What m. causes allows eye to focus on nearby objects via parasympathetic stimulation?
Ciliary m. contraction
After passing thru ciliary ganglion, how to sympathetic fibers enter the eye?
What m. do they innervate and what’s its function?
- Short and long ciliary nn.
- Dilator pupillae mm. –> dilate pupil
What are the 7 branches of the ophthalmic a. that Dr. Frystak cares about?
Lacrimal (taggable) Central retinal Long and short ciliary (choroidal) Supraorbital (taggable) Anterior ethmoidal Posterior ethmoidal Supratrochlear
What veins drain the orbit?
What hole do they pass thru?
Where do they drain to?
- Superior and inferior ophthalmic vv.
- Superior orbital fissure
- Cavernous sinus
What are the 3 layers of the eye, outside to inside?
Schlera, choroid, retina
What are responsible for the production of the eye’s aqueous humor?
Ciliary processes (in the ciliary body). - Distributed to ant and post compartments
What attaches the ciliary body to the lens?
Zonular fibers
What is the cause of Glaucoma?
Increasing IOP (intraocular pressure). Aqueous humor drainage is less than its production (produced in ciliary body)
- Compresses retina, optic n., BV’s
- Caused be decreased outflow thru canal of schlemm or increased production in aqueous humor
- Can dmg retina, painful, eventually can cause blindness
- Sx: blurred vision, halos around bright objects
Where is the constrictor pupillae m. located?
Pupillary aspect of the eye, circumferentially. (parasymp)
Where is the dilator pupillae m. located?
Deep to constrictor pupillae, oriented radially. (symp)
Where is the vitreous body contained?
Postremal chamber
What are the functional layers of cells in the retina, in the order that light hits them?
- Ganglion cells (cell bodies, pass to optic n.)
- Interneurons and bipolar cells
- Photoreceptors (lie adjacent to pigmented epithelium)
What are Muller cells, basically?
Supporting cells of the retina
Do rods or cones have higher amplification?
Rods
Which has higher temporal resolution, rods or cones?
Cones
Which take more light to saturate, cones or rods?
Cones
Which have more pw convergence (lower acuity), rods or cones?
Rods
Describe what’s present at the fovea.
Avascular zone consisting mainly of just a cone layer.
Where does the optic n. leave the sclera?
Lamina cribrosa (of the sclera)
What is the name of the retina overlying the lamina cribrosa?
Optic papilla/optic disc/blind spot
Where do the central a. and v. of the retina run thru?
Center of the optic n.
Where does the central v. of the retina normally drain to?
Cavernous sinus
Do the oblique mm. insert on the medial or lateral side of the eyeball?
Lateral
What does the outer-most layer of the retina consist of? (resting on the choroid)
Pigmented epithelial cells
What forms the blood-retinal barrier?
Tight junctions b/w Muller cells (of the retina)
What is responsible for the yellow and white secretion sometimes found in the eye upon arising after a night’s sleep?
The lacrimal caruncle (contains the sweat glands, sebaceous glands, and cilia)
What accounts for the “sniffling” which is necessary to keep the draining tears within the nasal cavity during crying.
Anterior drainage of the nasolacrimal duct
- “overflow” from the ductal system
Describe the pathway of tears from the lacrimal gland.
Lacrimal gland (ducts–>)
Superior palpebral fornix –>
Puncta lacrimali (drain opening, sup and inf medially) –>
Lacrimal canaliculus (sup and inf) –>
Lacrimal sac (fossa of lacrimal bone) –>
Nasolacrimal duct –> nasal sinus
What is the flow of aqueous humor? What does it go through?
Post –> ant
- goes thru pupil
What are the major nn. found in the orbit?
- CN II
- CN III
- CN IV
- CN V-1
- CN VI
(all travel through SOF) - Sympathetics & parasympathetics
What types of information do short ciliary nn. carry to the eye?
- Postganglionic symp
- Postganglionic parasymp
- General sensory (afferent) fibers
