Orbits Flashcards
Periorbita
Orbital fascia
Bony walls of the orbit
Frontal bone Sphenoid Maxillary Palatine Lacrimal Ethmoid Zygomatic
How does CN V2 travel through the orbit
Inferior orbital fissure - infraorbital groove (maxillary bone) - infraorbital foramen - face, teeth
What structures run through the optic canal?
Optic nerve
Opthalmic artery
What structures run through the superior orbital fissure?
V1
Oculomotor
Trochlear
Abducens
Sclera
White wall of eye
Lacrimal caruncle
Small mass of mucous membrane at medial corner of eye
Superior/inferior lacrimal puncta
Small openings above and below caruncle for collection of tears
Tarsal plates
Bands of connective tissue that strengthen the eyelids
Lacrimal canaliculi
Transports tears from lacrimal puncta to lacrimal sac
Lacrimal sac
Collects tears
Nasolacrimal duct
Drains tears into nasal cavity
Cornea
Transparent anterior surface of the eye
Lens
Focuses light on the retina
Retina
Posterior lining of the eye with specialized photoreceptors
Posterior cavity of the eye
Cavity posterior to the lens
Vitreous body
Transparent, gelatinous substance within posterior cavity
Anterior cavity of the eye
Space anterior to the lens
Anterior chamber of the eye
Space between cornea and iris
Aqueous humor
Clear, watery fluid in anterior cavity
Posterior chamber of the eye
Space between lens and iris
Ciliary muscle
Smooth muscle that changes shape of lens
Contraction = loosen suspensory ligaments = lens thickens
Suspensory ligament (eye)
Connects ciliary muscle to capsule of lens
Sphincter pupillae
Circular smooth muscle that affects size of pupil
Works in conjunction with dilator pupillae
Contraction = constrict pupil
N: parasympathetics (Oculomotor CN III)
Canal of Schlemm
Drains fluid from anterior cavity
Between angle of cornea and iris
What causes glaucoma?
Blockage of the canal of Schlemm
Conjuctiva
Mucous membrane of anterior eye and eyelids
Sits on top of cornea and folds over to inside of eyelid
Levator palpebrae superioris
Skeletal muscle that elevates upper eyelid
Superior tarsal (Mueller’s) muscle
Smooth muscle that helps elevate the upper eyelid
Dilator pupillae
Smooth muscle that controls size of pupil with sphincter pupillae
Contraction = dilation of pupil
Controlled by sympathetics
What shape is the lens for distant vision?
Flattened - ciliary muscle relaxed
What shape is the lens for closeup vision?
Thickened - ciliary muscle contracted
Fovea
Depression in retina that represents area of highest visual acuity
Common tendinous ring
A fibrous cuff at the apex of the orbit
The 4 recti muscles arise from here
Surrounds the optic canal and part of the superior orbital fissure
Superior rectus
Common tendinous ring - superior aspect of eyeball
A: elevate, adduct
N: oculomotor (III)
Inferior rectus
Common tendinous ring - inferior aspect of eyeball
A: depress, adduct
N: oculomotor (III)
Medial rectus
Common tendinous ring - medial eye
A: adduct
N: oculomotor (III)
Lateral rectus
Common tendinous ring - lateral eye
A: abduct
N: abducens (VI)
Superior oblique
body of sphenoid bone - medial aspect of orbit - trochlea - superior eye
A: depression, abduct
N: trochlear (CN IV)
Inferior oblique
anterior/medial part of the floor of the orbit - inferior eye
A: Elevate, abduct
N: oculomotor (CN III)
Levator palpebrae superioris
lesser wing of sphenoid bone (near optic canal) - superior tarsus (upper eyelid)
A: raises upper eyelid
N: oculomotor (III)
Ptosis
drooping of the upper eyelid
The lateral retina gets visual information from the _______ field of vision and projects onto the _______ side of the brain
the lateral retina gets visual info from the MEDIAL field of vision and projects onto the SAME SIDE of the brain
the medial retina recieves information from the _______ visual field and project onto the _______ side of the brain
the medial retina recieves info from the LATERAL visual fields and projects onto the OPPOSITE SIDE of the brain
Right optic nerve lesion
cause complete blindness in right eye
optic chiasm lesion
would lose function of the medial retina - cannot see both lateral fields of vision
Right optic tract lesion
Lose function of the right lateral retina and the left medial retina
Lose vision of the right medial view and the left lateral view
How do parasympathetics of the oculomotor nerve (III) travel to the lens and pupil?
synapse in the ciliary ganglion - short ciliary nerves - eyeball
Branches of the opthalmic division of trigeminal (V1)
frontal
nasociliary
lacrimal
Frontal nerve
Branch off of opthalmic division of trigeminal (V1)
Splits into supraorbital and supratrochlear
Sensation from forehead
Nasociliary nerve
Branches into anterior and posterior ethmoidal - sensation from ethmoid air cells, nasal cavity and bridge of nose (external nasal nerve)
Turns into infratrochlear when it exits orbit - sensation from skin around medial eye
Sensation from cornea
Also branches into long ciliary nerves
Lacrimal nerve
Sensation from skin outside the eye
Also used by facial nerve to get parasympathetics to lacrimal gland
Long ciliary nerves
Branch from nasociliary nerve (v1) - back of eye
Medial side of optic nerve
Carry sympathetic and sensory fibers
Short ciliary nerves
Ciliary ganglion - back of eye
Lateral to optic nerve
Carry sympathetic, parasympathetic, and general sensory nerve fibers
How does the maxillary division of trigeminal (V2) travel through the orbit?
**Does nothing in the orbit
Gives rise to zygomatic nerve in lateral orbit and travels along floor as infraorbital nerve
Which branches of the maxillary division of trigeminal (V2) carry sensation from the skin of the face?
V2 branches into zygomatic
Zygomatic branches into zygomatico temporal, zygomaticofacial, and infraorbital nerves
superior alveolar nerves
branch of maxillary divison of trigeminal (V2)
Sensation from mx teeth
Main artery of the orbit
ophthalmic artery
Name branches of the opthalmic artery (which is a branch off of internal carotid)
lacrimal supraorbital supratrochlear anterior/posterior ethmoidal ciliary central retinal
name the arteries that form collateral circulation around the outside of the orbit
supraorbital supratrochlear angular infraorbital transverse facial superficial temporal
Describe the path of venous drainage from the orbit
superior/inferior ophthalmic veins
drain into cavernous sinus posteriorly
drain into pterygoid plexus inferiorly
what provides a pathway of the spread of infection from the face to the venous sinuses?
communication of angular (facial) vein and opthalmic veins
What can be some consequences of blowout fractures
medial and inferior walls of orbit are very thin
Blow to the eye = contents of orbit (esp. periorbital fat) may enter sinuses
medial protrusion - ethmoid sinuses
inferior herniation - maxillary sinuses