13.3 Orbital Contents Flashcards
Identify the Periorbita
a thick connective tissue sheath containing the orbital contents
Identify the Frontal nerve. From what cranial nerve does this branch?
- What does the frontal nerve innervate?
- Locate and name the 2 terminal branches of the frontal nerve.
- Frontal nerve comes from CN V1. Should be located on top of the levator palpebrae superioris.
- Frontal nerve’s terminal branch into supraorbital. This does sensory to the skin of the upper eyelid and forehead.
- Supratrochlear and Supraorbital nerves.
Identify the extrinsic muscles of the eye: Levator palpebrae superioris Superior rectus Superior oblique Medial rectus Lateral rectus Inferior oblique Inferior rectus What nerve innervates these muscles and what is the function of each?
- Superior oblique is innervated by CN IV (Trochlear)
- Lateral rectus is innervated by CN VI (Abducent)
- The rest are innervated by the oculomotor nerve (Levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique)
Levator palpebrae superioris: Initial opening of eye
Superior rectus: elevates, slight adduction
Superior oblique: down and out
Medial rectus: adduction
Lateral rectus: abduction
Inferior oblique: up and out
Inferior rectus: depresses, slight adduction
Identify the lacrimal gland, nerve, and duct.
From where does the lacrimal nerve branch?
It is a branch off of CN V1 (Ophthalmic)
Identify the trochlear nerve (CN IV) in the orbit.
Describe its course and what muscle it is innervating.
runs parallel to the medial wall and enters the superior oblique muscle on its superior surface at its proximal end
Identify the abducent nerve (CN VI) in the orbit.
Describe its course and what muscle it is innervating.
entering the lateral rectus m. on its medial surface
Identify the Nasociliary nerve.
-From what nerve does this stem?
-Describe its course
-Locate the anterior and posterior ethmoidal branches
-Locate the ciliary ganglion as well as the long and short ciliary nerves.
What do each of these nerves innervate?
- Nasocilliary nerve branches off of CN V1 (Ophthalmic).
- Passes from lateral to medial as it courses anteriorly from the apex of the orbit superficial to the optic nerve.
- Anterior and Posterior Ethmoidal nerves: carry parasympathetics (from the pterygopalatine ganglia via CN VII) and sensory to the mucosa of the sphenoid sinus and ethmoid air cells.
- Long ciliary nerve: carries sympathetics into the eye.
- Short ciliary nerve: carries postsynaptic parasympathetics from the ciliary ganglion to the eye (from CN III)
Identify the optic nerve (CN II).
Describe the function of this nerve.
Sensory for vision through the optic canal.
Identify the ophthalmic artery.
Describe its root and main function.
Understand the branches from the ophthalmic artery and their functions
-The blood supply to the eye and orbit is primarily through the ophthalmic artery, a branch of the internal carotid
- a. The central retinal artery which runs deep to the dura and pierces the optic nerve near the eyeball, supplies all retinal neurons (except the rods and cones)
b. Long and short posterior ciliary arteries form a choroid capillary plexus supplies the rods and cones of the eye.
c. Lacrimal artery –supplies the lacrimal gland.
d. Branches that exit the orbit and supply the face or nasal cavity may include the supraorbital, supratrochlear, dorsal nasal, and anterior and posterior ethmoid arteries.
e. Several anastomoses may include a branch off the lacrimal to the middle meningeal (maxillary) and the supratrochlear to the dorsal nasal (angular).
Identify the superior and inferior ophthalmic veins.
Describe the course of venous drainage in the orbit.
Highly variable, with most of return into the cavernous sinus from the superior ophthalmic. Often see some return to the external jugular from the facial via the inferior ophthalmic (and sometimes supratrochlear into the angular). These anastomotic pathways can result in the “danger triangle”, the potential for a superficial infection to spread into the cavernous sinus.
Identify the occulomotor nerve.
Describe its dual function in this region.
Locate the superior and inferior divisions of the occulomotor nerve. Which muscles does each branch innervate?
- Motor to most extraocular muscles
- Parasympathetics to smooth muscle inside eye (the sphincter pupillae and ciliary muscles). The Parasympathetics make their way to the ciliary ganglian, then postsynaptics get to the eye via the short ciliary branches of V1 (Sympathetics can travel on the short and long ciliary branches).
- Superior branch: superior rectus, and the levator palpebrae superioris
- Inferior branch: inferior rectus, medial and lateral rectus
Describe the superior tarsal muscle.
the anterior-most fibers of the levator palpebrae superioris
Locate and describe the lacrimal sac
in the medial corner of the orbit. Fluids accumulate here after passing thru the lacrimal caliculi and prior to exiting the eye via the nasolacrimal duct.
Identify and describe the function of each of the following structures in the eye:
- Pupil
- Sclera
- Conjunctiva
- Iris
- Cornea
- Anterior and posterior chambers
- Vitreous body
- Retina
- Choroid
- Ciliary body
- Ciliary muscle
- Cilliary processes
- Ora serrata
- Pupil
- Sclera –opaque, white part of the visible eye where the extrinsic muscles attach.
- Conjunctiva
- Iris: the contractile diaphragm that lies on the surface of the lens, has two layers (Sphincter pupillae and Dilator pupillae)
- Cornea –transparent layer covering the lens.
- Anterior and Posterior chambers
- Vitreous body: fluid of the eye (like CSF)
- Retina
- Choroid –pigmented membrane between the sclera and retina.
- Ciliary body and muscle: The vascular portion secretes the aqueous humor. Accommodation. Innervation CN III
- Ciliary processes
- Ora serrata
