The Orbit And Eye Flashcards
What is the palpebral portion of the orbicularis oculi muscle?
Extends from the medial to the lateral palpebral ligament Functions in gentle closing of the eyelid
What is the lacrimal portion of the orbicularis oculi?
Extends from the posterior lacrimal crest to the tarsal plates of the lids and lacrimal sac Increases amount of lid contact to the surface of the eyeball and dilates the lacrimal sac
What innervates the levator palpebrae superioris muscle?
GSE fibers of CN III
What are the 5 layers of the eyelid?
Skin Subcutaneous tissue Muscular layer containing the orbicularis oculi, levator palpebrae superioris and tarsal muscle Palpebral fascia Conjunctiva
What is the tarsal muscle of Muller innervated by?
Postganglionic sympathetic fibers Preganglionic fibers originating at the level of T1
Destruction of the oculomotor nerve or one of its branches to the levator palpebrae superioris can result in what?
Paralysis of the LPS and complete ptosis
What is Horner’s syndrome?*
Usually involves paralysis of the tarsal muscle Results in slight ptosis Leads to miosis (pupillary constriction due to paralysis of the dilator pupillae muscle), enopthalmos (due to paralysis of the orbitalis muscle of Muller which has a slight protrusion function), Anhidrosis and blushing of the skin on the face may also be present Interruption of pupillary dilation pathway can result in this
Which structures are involved in draining tears from the surface of the eye?
Lacrimal gland, lacrimal duct, lacrimal canaliculi, lacrimal sac and nasolacrimal duct
What is the lacrimal gland?
An oval shaped gland resting in the lacrimal fossa of the orbit It’s secretions (tears) keep the surface of the cornea moist
What are lacrimal canaliculi?
Small L shaped tubes that have an opening called the lacrimal punctum which forms the apex of the lacrimal papilla Drain tears from the surface of teh eyeball to the superolateral aspect of the lacrimal sac via a common sinus (sinus of Maier) Lacerations of the canaliculi require prompt surgical attention
What is the lacrimal sac?
An elongated tear dropped shaped membranous sac located between the anterior and posterior lacrimal crest Receives lacrimal canaliculi superolateral and is continuous with the nasolacrimal duct inferiorly
Describe the parasympathetic innervation to the lacrimal gland
The superior salivatory nucleus sends preganglionic fibers via CN VII, greater superficial petrosal and vidian nerve to the sphenopalatine/pterygopalatine ganglion where they synapse Postganglionic fibers course to the lacrimal gland via the maxillary, zygomatic and lacrimal nerves
Explain sympathetic innervation to the lacrimal gland
Postganglionic fibers from the superior cervical ganglion travel along the internal carotid plexus and give rise to the deep petrosal nerve which fuses with the greater petrosal to form the Vidian N Fibers course through the pterygopalatine ganglion without synapsing and distribute to the lacrimal gland via maxillary, zygomatic and lacrimal nerve route
What is traumatic optic neuropathy?
Intracanalicular portion of the optic nerve is vulnerable to ischemia secondary to orbital fracture Relatively low incidence to head trauma but has a direct impact on the optic nerve, opthalamic A and vascular supply to the retina via the central retinal artery
Blow out fractures of the floor of the orbit may by due to what?
Trauma to the front of the eyeball or a depressed fracture of the zygomatic bone which is displaced medially
What do blow out fractures cause?
Herniation of the certain orbital structures (such as the periorbita, the inferior oblique and inferior rectus muscles, or the orbital fat pad) into the maxillary sinus
In which direction are those with a blow out fracture not able to move their eyes?
Won’t be able to move their eye to the side of injury
What is a Le Forte type I fracture?
Transverse fracture of the maxillae just above the alveolar processes Moveable upper dental arch with some teeth missing
What is a Le Forte type II fracture?
Pyramidal shaped fracture of the maxillae usually involving part of the medial margin of one of the orbits
What is a Le Forte type III fracture/craniofacial dysfunction?
Extensive transverse fractures of the face involving many facial bones and both orbits (panda bear appearance-two black eyes and swollen lower face) Basically the face has been separated from the base of the skull
What innervates the extra-ocular muscles?
All innervated by the oculomotor nerve except the superior oblique (IV) and lateral rectus (VI) SO4, LR6 and remainder 3
What is the periorbita continuous with?
Endosteal dura