Orbit and Meninges Flashcards
What are the seven bones of the orbital cavity?
Palantine, ethmoid, lacrimal, maxillary, zygomatic, frontal, sphenoid
What are the layers of the eyelid from superficial to deep?
Skin Subcutaneous tissue Orbicularis occuli Orbital septum Tarsus Conjunctiva
What causes racoon eyes?
Blood in the potential space of the thin subcutaneous tissue of the eyelid
What is the voluntary muscle of the eyelid and how do you know if it is damaged?
Palpebral part of the orbicularis oculi (innervated by CN7). Inability to blink/close upper eyelid and lower eyelid droops away, associated with corneal ulcers and spillage of tears
What is Horner’s Syndrome?
Loss of sympathetic ganglion fibres resulting in ptosis, miosis and anhydrosis
Which two muscles raise the eyelid and what innervates them?
Levator palpebral superioris (CN3) full ptosis
Superior tarsal muscle (postganglionic sympathetic fibres of superior cervical ganglion) partial ptosis
What arrives in the orbital cavity via the optic canal?
Optic nerve and ophthalmic artery
What is the common tendinous ring?
Thickening of periosteum that surrounds the optic canal and the superior orbital fissure. It is the point of origin for the extra-ocular muscles
What enters the orbital cavity through the superior orbital fissure?
Superior ophthalmic vein Inferior ophthalmic vein (maybe) Sympathetic fibres from cavernous plexus Superior div. of CN3 Inferior div. of CN3 CN4 Ophthalmic (V1 of CN5) CN6
What enters the orbital cavity through the inferior orbital fissure?
Inferior ophthalmic vein (maybe) Infra-orbital vein Infra-orbital artery Zygomatic branch of maxillary V2 of CN5 Ascending branches from pterygopalantine ganglion
List the extra ocular muscles of the eye
Superior rectus Inferior rectus Lateral rectus Medial rectus Superior oblique Inferior oblique Levator palpebral superioris
Which artery closes in diabetes causing blindness?
Central retinal artery
What is the arterial and venous supply to the eye?
Internal carotid artery, ophthalmic artery, central retinal artery
Superior and inferior ophthalmic vein
What is the “danger triangle” of the face?
Lips to nasion- due to communication between facial vein and cavernous sinus
What are the three branches of the ophthalmic nerve?
Lacrimal nerve
Frontal nerve
Nasociliary nerve
Which nerves will an increased intracranial pressure effect?
First, abducens, then trochlear, then optic
How do the meninges change from the skull to spinal chord?
Cranial dura is double layered-periosteal and meningeal. Spinal dura is single layered- only meningeal layer
What is a key difference between the pia and arachnoid mater?
Pia invests into the surface of the brain. Arachnoid mater does not enter grooves and fissures except for the longitudinal fissure
When to the two cranial dural layers separate from each other?
To form intracranial venous structures and dural partitions (project inwards and completely divide parts of the brain eg. falx cerebri
What is the blood supply to the dura?
Anterior, posterior and middle meningeal artery
How does the middle meningeal artery exit the skull and where is it found?
Travels through foramen spinosum-the anterior branch of the middle meningeal artery crosses the pterion
What is the innervation of the dura mater?
V1, V2, V3, CN10 and 1st, 2nd and 3rd cervical nerves
Describe the venous drainage of the brain
Cerebellar veins, diploic veins and emissary veins drain into dural venous sinuses, which drain into the internal jugular veins
Where do the emissary veins run and why are they relevant?
Between the outside of the cranial cavity and the dural venous sinus-can cause infections to enter cranial cavity as they have no valves
