Orbit Anatomy Flashcards
What does the ophthalmic artery branch off from?
The internal carotid artery
Throwback: where does the lacrimal duct drain?
The inferior meatus
What does the sphincter pupillae do? Is it under parasympathetic or sympathetic control?
Constricts the pupil
It is under parasympathetic control (CN III)
What are the lacrimal canaliculi?
Superior and inferior ducts that drains tears from the lacrimal papilla to the lacrimal sac
What is this structure?
Superior rectus muscle
What are the zonule fibers?
they anchor the lens to the ciliary body.
The lateral rectus muscle is innervated by what cranial nerve?
Abducens, CN VI
What artery in the eye is an anatomical end artery?
The central retinal artery
What are the three branches of the ophthalmic nerve?
- Frontal (further branches)
- Nasociliary
- Lacrimal
What is this structure?
Frontal nerve
What nerves are responsible for the corneal reflex?
Afferent/sensory: Nasociliary branch of V1
Motor: CN VII - Facial
What four branches does the ophthalmic artery give off?
- Lacrimal artery
- Long and short ciliary arteries
- Supraorbital artery
- Supratrochlear
What does the lens do?
it refracts light to focus it on the retina
What innervates the superior oblique muscle?
CN IV - Trochlear
What is the point of entry of the optic nerve into the retina called?
The optic disc
What does the nasociliary nerve innervate?
The ethmoidal air cells
How many layers is the retina?
10
What does the dilator pupillae muscle do? Is it under parasympathetic or sympathetic control?
It increases the size of the pupil
It’s under sympathetic nervous system control
What is the retina?
the neurosensory layer of the eye
What is this structure?
optic nerve
The superior oblique muscle is innervated by what cranial nerve?
Trochlear, CN IV
Where does the ophthalmic division of the trigeminal nerve (V1) enter the orbit?
Superior orbital fissure
What do the tarsal glands do?
They are responsible for the supply of meibum, an oily substance that prevents evaporation of the eye’s tear film
Where do all four rectus muscles attach?
The fibrous Annulus Ring of Zinn (annulus tendinous)
What is the macula?
An oval yellowish area surrounding the fovea
What innervates the lateral rectus muscle?
CN VI - Abducens
If the ciliary muscle is contracted, what are the zonular fibers doing? What is the effect on the lens and vision?
The zonular fibers are relaxed
The lens is thicker so you can see closer up
What innerveates the lacrimal gland?
CN VII - Facial
If the ciliary muscle is relaxed, what are the zonular fibers doing? What is the effect on the lens and vision?
The zonule fibers will be contracted
The lens is flattened so you can look at something far away
What is the lamina papyracea? What bone is it part of?
A smooth, oblong, and very thin piece of bone that covers the middle and posterior ethmoidal cells and forms a large part of the medial wall of the orbit.
It is part of the ethmoid bone
What is this structure (tip of upper probe)?
The ciliary ganglion
What muscle is responsible for blinking?
Levator palpabrae superioris
Where is the abducens nerve found?
On the medial side of the lateral rectus muscle (which it innervates!)
Where can you find CN IV in the orbit?
On top of the superior oblique muscle
You cannot pronounce a person with this reflex brain dead
Corneal reflex
What are the branches of the frontal nerve?
Supratrochlear nerve and the supraorbital nerve
What is muscle is responsible for accomodation? What innervates that muscle?
Ciliary muscle
Parasympathetics of CN III
What is the venous drainage of the orbit? Where do these empty into?
Superior and inferior ophthalmic veins that drain into the cavernous sinus (then the superior petrosal sinus, sigmoid sinus, and finally the internal jugular vein)
What is the ciliary ganglion?
a parasympathetic ganglion located just behind the eye in the posterior orbit.
The oculomotor nerve coming into the ganglion contains preganglionic axons from the Edinger-Westphal nucleus (a part of the brainstem) which form synapses with the ciliary neurons. The postganglionic axons run in the short ciliary nerves and innervate two eye muscles: the sphincter pupillae & the ciliaris contracts
What are the medial rectus, superior rectus, inferior rectus, and inferior oblique muscles innervated by?
CN III, occulomotor
What structure is this?
levator palpebrae superioris muscle
What muscle is responsible for each of these movements?
What nerve palsy is this?
CN VI - Abducens nerve palsy
There is unopposed pull by the medial rectus
What is Horner’s syndrome?
Drooping of the eyelid, lack of pupil dilation
What does the lacrimal gland secrete?
Lacrimal fluid - a watery, saline solution containing lysozyme that moistens the surfaces of the conjunctiva and cornea
What nerve palsy is this?
CN III - Occulomotor palsy
Downward and outward gaze, dilated pupils and ptosis (drooping of upper eye lid)
What is the area of most acute vision in the eye?
The fovea centralis
What is this structure?
Lacrimal nerve
Where are the palpebral and bulbar conjunctiva?
The bulbar conjunctiva is on the white portion of the eye
The palpebral conjunctiva is on the inner surface of the eye
Note: both innervated by V1
What is the lacrimal caruncle?
the small, pink, globular nodule at the inner corner (the medial canthus) of the eye. It is made of skin covering sebaceous and sweat glands
What is located in the center of the optic nerve?
The central retinal artery
What is the corneal reflex?
Involuntary blinking of the eyelids elicted by stimulation of the cornea
Stimulation should elict both a direct and indirect or consensual response from the other eye
What is this structure?
Trochlear nerve
What are the three layers of the eyeball?
- Fibrous outer layer: 5/6 sclera, 1/6 cornea
- Vascular layer: choroid, ciliary body & iris
- Inner layer: retina (optic part + fovea centralis)
What is this structure?
Supraorbital nerve
What is this structure?
Trochlea
What nerve palsy is this?
CN IV - Trochlear nerve palsy
Unopposed pull of the superior rectus muscle
What is the limbus?
The source of new cells to renew the cornea
What is this structure?
Supratrochlear nerve
What innervates the conjuctiva?
V1
