SM_06a: Orbit Anatomy and Development Flashcards
____ makes up roof of orbit
Frontal bone makes up roof of orbit
____ and ____ make up floor of orbit
Maxilla (mostly) and zygomatic bone make up floor of orbit
____ and ____ make up the lateral wall of the orbit
Zygomatic bone and greater wing of sphenoid make up the lateral wall of the orbit
____, ____, and ____ make up the medial wall of the orbit
Maxilla, lacrimal bone, and ethmoid bone make up the medial wall of the orbit
____ separates sphenoid wings, while the ____ traverses the lesser wing
Superior orbital fissure separates sphenoid wings, while the optic canal traverses the lesser wing
Orbit is bounded medially and inferiorly by ____ and ____
Orbit is bounded medially and inferiorly by ethmoid and maxillary paranasal air sinuses
(these spaces have implications for fractures and the spread of infections)
Blow-out fractures of the orbital wall are when ____
Blow-out fractures of the orbital wall are when orbital contents extend out of the ethmoid sinus into the maxillary sinus
(blood can also accumulate in the maxillary sinus)
Eye develops from the ___, ___, and ___
Eye develops from the lens placode, optic cup, and head mesenchyme
- Lens placode sinks under the surface as the lens vesicle is surrounded by the optic cup
- Head mesenchyme from the neural crest begins to condense around the optic cup to form the connective tissue elements
Coloboma is ____
Coloboma is retention of the ventral cleft
(may involve iris - keyhole pupil - or whole ventral sclera)
Two layers of the optic cup form the ____, while the mesenchyme forms the ____, ____, ____, and ____
Two layers of the optic cup form the two layers of the retina, while the mesenchyme forms the sclera, cornea, choroid, and meninges
____ is main artery of the eye
Central artery of the retina is main artery of the eye
Optic cup is extension of the ____
Optic cup is extension of the neural crest
- Optic nerve (II) is a brain fiber tract surrounded by meninges and CSF unlike a typical nerve
- Two layers of optic cup form neural and epithelial layers of retina
- Two layers of optic cup never tightly fused, allowing detached retina to occur
____ divides the aqueous humor and vitreous humor
Iris divides the aqueous humor and vitreous humor
(both have lots of glycosaminoglycans)
Cornea is ____ and is nourished by ____
Cornea is avascular and nourished by aqueous humor
Aqueous humor is produced in the ____ and passes through the pupil to the ____ and then to the venous ____
Aqueous humor is produced in the posterior chamber and passes through the pupil to the anterior chamber and then to the venous Canal of Schlemm
Narrow angle glaucoma involves ____
Narrow angle glaucoma involves increased aqueous humor pressure
____ is the optic nerve blind spot, while the ____ in the ____ is the area of most acute vision
Optic disc is the optic nerve blind spot, while the fovea centralis in the macula lutea is the area of most acute vision
Dilated pupil may be indicative of ____
Dilated pupil may be indicative of increased intracranial pressure
(iris has circular sphincter for the pupil and a radiator dilator muscle, lens is achnored by taut suspensory ligaments, and contraction of the ciliary muscle allows the lens to round up for close-up vision)
Describe the path of the lacrimal apparatus
Lacrimal apparatus
- Lacrimal gland
- Conjunctival sac
- Lacrimal papillae with lacrimal puncta
- Lacrimal canaliculi
- Lacrimal sac
- Nasolacrimal duct
- Inferior meatus of nasal cavity
____ is innervated by the oculomotor nerve, and the ____ helps raise the eyelid (sympathetic innervation)
Levator palpebrae superioris is innervated by the oculomotor nerve, and the superior tarsus muscle helps raise the eyelid (sympathetic innervation)
Tarsal gland obstruction forms a ____, while ciliary gland obstruction forms a ____
Tarsal gland obstruction forms a chalazion, while a ciliary gland obstruction forms a sty
Extraocular muscles from head somites include ____, ____, and ____
Extraocular muscles from head somites include rectus (medial, lateral, superior, inferior), levator palpebrae superioris, and obliques (superior, inferior)
(superior oblique not visible on lateral view)
Rectus muscles originate from ____
Rectus muscles originate from anulus tendineus
- Fibrous ring that surrounds the optic, oculomotor, abducens, and nasociliary nerves
- Only trochlear nerve passes above the ring to the superior oblique muscle
Elevators of the pupil include the ___ and ___, while depressors of the pupil include the ___ and ___
Elevators of the pupil include the superior rectus and inferior oblique, while depressors of the pupil include the superior oblique and inferior rectus
Adductors of the pupil include the ____, ____, and ____, while abductors of the pupil include the ____, ____, and ____
Adductors of the pupil include the superior rectus, medial rectus, and inferior rectus, while abductors of the pupil include the superior oblique, inferior oblique, and lateral rectus
Align visual axis with ____ to test a muscle
Align visual axis with line of pull of the muscle to test a muscle
(brings muscle to its most efficient position for elevation/depression with its synergist in its most inefficient position)
Describe testing the oculomotor nerve
Testing the oculomotor nerve
- No levator palpebrae superioris function
- Pupil dilated (no parasympathetics)
- Pupil stays in the down and out quadrant because lateral rectus / superior oblique are still working
Abducens palsy is ___
Abducens palsy is inability to abduct the pupil
(VI has a long intracranial course and is often damaged as it gets stretched over the petrous part of the temporal bone)
CN VI goes to the ____
CN VI goes to the lateral rectus
CN IV goes to the ____
CN IV goes to the superior oblique
CN III goes to ____
CN III goes to all other muscles of the eye
V1 (general sensory) turns into the ___, ___, and ___
V1 (general sensory) turns into the frontal, lacrimal, and nasociliary nerves
(frontal becomes supraorbital/supratrochlear)
____ and ____ are on the left, while ____ and ____ are on the right when looking ventrally at the eye apparatus
Nasociliary nerve and ciliary ganglion are on the left, while motor nerves and lacrimal nerve are on the right when looking ventrally at the eye apparatus
Describe motor nerves and the parasympathetic pathway for the eye
Motor nerves and the parasympathetic pathway for the eye
- Ciliary ganglion connected to oculomotor nerve
- Parasympathetics exit the brain with III -> synapse in ciliary ganglion -> follow short ciliary branches of V1 to ciliary muscle and pupil constrictor
- Short ciliary nerves (V1) and ciliary ganglion receive sensory fibers from the nasociliary nerve and presynaptic parasympathetics from III
- Postsynaptics and sensory fibers follow short ciliary nerves to the eye
Parasympathetics for lacrimal secretion exit the brain with the ___, NOT the ___
Parasympathetics for lacrimal secretion exit the brain with the facial nerve (CN VII), not the lacrimal nerve
(synapse in pterygopalatine ganglion -> follow V2 branches to the lacrimal gland)
Special sensory nerve related to eye function is ___
Special sensory nerve related to eye function is optic nerve (II) for vision
General sensory nerve related to eye function is ___
General sensory nerve related to eye function is ophthalmic division (V1) of trigeminal nerve
(lacrimal nerve, frontal nerve - supraorbital and supratrochlear, nasociliary - long and short ciliary, anterior and posterior ethmoidal)
Branchiomotor nerve related to eye function is ___
Branchiomotor nerve related to eye function is facial nerve (VII) to orbicularis oculi for closing eyelids (and origin of parasympathetics to lacrimal gland)
Somatomotor nerves related to eye function include ___, ___, and ___
Somatomotor nerves related to eye function include
- Trochlear nerve (IV) to superior oblique (eye down and out)
- Abducens nerve (VI) to lateral rectus for pupil abduction
- Oculomotor nerve (III) to all other muscles including levator palpebrae superioris for opening eyelids)
Sympathetic nerves related to eye function originate from the ____, travel up the ____, synapse, then follow arteries to the ____ and ____
Sympathetic nerves related to eye function originate from the thoracolumbar outflow, travel up the sympathetic trunk, synpase, then follow arteries to the dilator of the pupil and superior tarsus muscle
Parasympathetics for eye function include ____, ____, and ____
Parasympathetics for eye function include
- Pupil constrictor (III to ciliary ganglion to short ciliary nerve)
- Ciliary muscle for close-up vision (accomodation)
- Lacrimal gland (VII to V2 to terminal lacrimal branches)
Arteries of the orbit mostly follow ____, while the ____ travels with the optic nerve through the optic canal and the ____ travels within the optic nerve to retina
Arteries of the orbit mostly follow trigeminal nerve branches, while the ophthalmic artery travels with the optic nerve through the optic canal and the central artery of the retina travels within the optic nerve to retina
Describe the pathway of venous blood from the opthalmic veins
Patbway of venous blood
- Ophthalmic veins and veins from deep in the brain
- Cavernous sinus
- Superior and inferior petrosal sinuses
- Beginning and end of the sigmoid sinuses
