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177 Cards in this Set
- Front
- Back
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Describe the orbit:
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Pyramidal shaped bony cavity
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What 6 types of structures does the orbit contain?
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-Eyeballs
-Muscles -Nerves -Vessels -Fat -Lacrimal apparatus |
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How are the walls of the orbit oriented?
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Medial walls are parallel to each other; (0' angle)
Lateral walls perpendicular (90' angle) |
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What are the 4 orbit margins and what bones make up each margin?
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1. Supraorb: frontal/sprbtlnotch
2. Lateral: frontal/zygomatic 3. Infraorb: zygomatic/maxilla 4. Medial: maxilla + frontal |
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What composes the orbit roof and what is its special feature?
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-Orbital plate of frontal bone
-Lacrimal fossa for lacrimal gland |
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What composes the orbit lateral wall and what is its special feature?
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-Zygomatic bone + greater wing of sphenoid
-Features the superior orbital fissure |
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what two compartments communicate via the sup orb fissure?
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Orbit + middle cranial fossa
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What passes through superior orbital fissure?
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CNs 3,4,V1,6
Opthalmic vein |
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What does the orbit floor consist of?
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Orbital plate of maxilla
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What 2 features in the orbit floor are noteworthy?
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-Inferior orbital fissure
-Infraorbital groove |
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What bone has the following:
-Superior orb fissure -Inferior orb fissure |
Sup = ethmoid
Inf = maxilla (NOT sphenoid) |
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What does the inferior orbital fissure allow to communicate?
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Orbit + pterygopalatine fossa and infratemporal fossa
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What passes through the inferior orbital fissure?
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-V2 maxillary nerve
-Inferior opthalmic vein (going to the pterygoid plexus) |
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What passes through the infraorbital groove?
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V2 branch - infraorbital nerve
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Components of medial orbit wall: (4)
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-Maxilla
-Lacrimal bone -Orbital plate of ethmoid -Body of sphenoid |
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Features of medial orbit wall (2):
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-Lacrimal groove
-Optic canal |
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What lies in lacrimal groove?
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Lacrimal sac
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What bone contains optic canal, what does it allow commun. w/?
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-Sphenoid bone
-Communcn w/ mid cranial fossa |
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What passes thru Optic canal:
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Optic nerve - CN II
opthalmic artery |
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What is the opening between the eyelids called?
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Palpebral fissure
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What are the corners of the eyes called?
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Angles (canthi) - med/lat
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What glands are in the eyelids skin?
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Ciliary - sweat/sebaceous
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4 Eyelid muscles:
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-Orbicularis oculi
-Submusc. connectv tissue - contin w/ galea aponeurotica. -Levator palpebrae superioris -Superior tarsal |
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Action of levator palebrae:
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voluntarily raises upper eyelid - deep fibers insert into superior tarsal plate.
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Superior tarsal muscle action:
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Smooth muscle; widens eyes to their fullest extent via sympathetic innervation.
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Function of glands in the tarsal plates:
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Secrete oily substance over tear layer; causes tears to spill over when eyes fill.
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What is the orbital septum?
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Membranous sheet connecting tarsal plates to orbital rim; continuous w/ periosteum.
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4 Main points re: conjunctiva:
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1. Transparent mucous membrane
2. Palpebral (inner eyelids) 3. Bulbar (over eyeball) 4. Fornix (crease betwn above 2) |
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6 Main parts of the Eyeball:
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1. Lens
2. Anterior cavity 3. Posterior cavity 4. Fibrous tunic 5. Vascular tunic 6. Neural/Retinal layer |
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Basic structure of the lens:
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Transparent, biconvex;
Tightly packed lens fibers; Lens capsule = basement membrane surrounding fibers. |
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What special structures facilitate change in lens shape during accommodation?
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Zonule fibers - parasympathetic innervation
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What common clinical problem occurs with the lens?
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Cataracts
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Where is Anterior cavity located; what does it contain?
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-In front of lens
-Contains aqueous humor |
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2 main areas of the anterior cavity:
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1. Anterior chamber
2. Posterior chamber |
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Where is the anterior chamber?
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Between posterior surface of cornea, and anterior surface of lens/iris.
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Where is the posterior chamber?
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Between posterior surface of iris/lens, and suspensory ligament.
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Where is the posterior CAVITY?
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behind the lens
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What does the posterior cavity contain?
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Vitreous humor
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What are the 2 components of the fibrous tunic?
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1. Sclera (back 5/6)
2. Cornea (front 1/6) |
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Main functions of the sclera:
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-Maintains eyeball shape
-Insertion of extraocular muscles |
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Main functions of cornea:
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-Refraction
(transparent/avascular) |
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3 structures found in the vascular tunic:
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1. Choroid
2. Ciliary body 3. Iris |
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What is the choroid?
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-Dense capillary plexus w/ pigment cells
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Where is the choroid found?
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Between sclera/retina
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What is the ciliary body?
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The layer of the vascular tunic that produces aqueous humor and contains the ciliary muscle.
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What is the purpose of aqueous humor?
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provides nutrients to the avascular lens and cornea
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Where does aqueous humor from the ciliary body go?
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Passes through the pupil, drains into the venous sinus at the iridocorneal angle.
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What common clinical problem is associated with the ciliary body and aqueous humor?
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glaucoma
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How is the ciliary muscle connected to the lens?
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By zonule fibers.
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What type of muscle is the ciliary m?
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smooth muscle like a sphincter
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What does the ciliary muscle do?
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Controls the shape of lens.
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How exactly does the ciliary m work?
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1. Parasymp nerves stim it
2. Contraction decreases tension of zonule fibers 3. Lens curvature increases -> now u can see close up |
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What is the iris?
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A highly pigmented diaphragm extending over the anterior lens surface.
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What is the pupil?
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The hole in the middle of iris
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What 2 muscles control the iris?
What kind of nerves innervate each? |
-Sphincter pupillae; parasymp
-Dilator pupillae; sympathetic |
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What 2 types of layers make up the retina?
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1. Retinal pigment epithelium
2. Nerve fiber layer - forms optic nerve. |
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What are the 4 key components of the lacrimal apparatus?
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1. Gland
2. Puncta 3. Sac 4. Nasolacrimal duct |
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Where is the lacrimal gland and how is it situated there?
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-Superolateral orbit angle
-Levator palpebrae superioris aponeurosis splits gland into: -Orbital part (in lacrimal fossa of zygomatic bone) -Palpebral part (lateral upper eyelid) |
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Where does the lacrimal duct open into?
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Fornix
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Where does lacrimal fluid flow?
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From lateral upper fornix to lower medial Lacrimal Lake.
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What are lacrimal puncta?
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Small apertures withn lacrimal papillae elevations along each eyelid.
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Where does lacrimal fluid flow after entering lacrimal puncta?
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Into lacrimal canaliculi -> lacrimal sac
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What and where is the lacrimal sac?
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In the lacrimal fossa of the lacrimal bone; the opening of the nasolacrimal duct.
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Where does the nasolacrimal duct flow into?
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The inferior nasal meatus.
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What 2 major arteries feed the orbital region?
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1. Internal carotid
2. External carotid |
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What branch does the internal carotid send to the orbit?
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Opthalmic artery via optic canal
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What are the 6 main branches of the Opthalmic Artery?
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1. Central artery of retina
2. Lacrimal artery 3. Supraorbital artery 4. Supratrochlear artery 5. Dorsal nasal artery 6. Post/ant ethmoidal aa. |
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Where does the central artery of retina run?
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Within dural sheath of optic nerve's inferior surface; supplies the retina.
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Where does the lacrimal artery go and feed?
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To the lacrimal gland, conjunctiva and eyelids -> becomes the lateral palpebral artery.
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What happens to the lacrimal artery ultimately?
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Anastomoses w/ the zygomatic-orbital a. and facial artery (of external carotid)
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What does the Supraorbital artery supply?
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-Superior rectus m
-Levator palpebrae superioris |
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Where does the supraorbital a ultimately end up?
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Passes thru supraorbital notch to feed 6 things:
-forehead and scalp -medial canthus -diploe of frontal bone -periosteum & frontal sinus |
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What is the supratrochlear artery and what does it feed?
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Terminal branch of opthalmic artery; feeds forehead/scalp and pericranium.
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What is important about the dorsal nasal artery?
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-Supplies lacrimal sac and skin of the nose.
-Anastomoses with external carotid via infraorbital artery. |
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What 3 branches to the orbit come from the external carotid?
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1. Infraorbital artery
2. Zygomatico-orbital artery 3. Facial artery |
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What is the infraorbital artery a branch of?
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Maxillary
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What 3 things does infraorbital artery supply?
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1. Inferior rectus m
2. Inferior oblique 3. Lacrimal sac |
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What does the infraorbital a anastomose with?
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Dorsal nasal artery of internal carotid's opthalmic artery. Also the facial artery.
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What is the zygomatico-orbital artery a branch of?
What does it supply? |
The superficial temporal artery.
-Supplies orbicularis oculi muscle. |
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What does the zygomaticorbital artery anastomose with?
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Lacrimal artery (from opthalmic artery)
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What does the facial artery anastomose with?
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-Dorsal nasal artery
-Infraorbital artery |
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What 3 arteries does the transverse facial artery anastomose with?
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1. Facial
2. Infraorbital 3. Lacrimal |
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What are the 3 important veins of the orbit?
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1. Central vein of the retina
2. Superior opthalmic vein 3. Inferior opthalmic vein |
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Where does the central vein of the retina run/drain?
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With the optic nerve; drains into cavernous sinus or superior opthalmic vein.
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What does the superior opthalmic vein communicate w/?
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-Facial vein
-Supraorbital vein |
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What hole does the superior opthalmic v. pass through and where does it drain?
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Passes through superior orbital fissure to drain into cavernous sinus.
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What does the inferior opthalmic vein receive blood from?
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Inferior/medial parts of the orbit.
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What does the inferior opthalmic vein connect to and drain into?
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-Connects w/ superior opthalmic vein and/or drains via inferior orbital fissure into pterygoid plexus.
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What 2 sensory nerves carry optic information?
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1. CN II - Optic
2. CN V1 - Opthalmic |
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What functional modality is attributed to each optic sensory nerve?
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Optic = special somatic afferent
Opthalmic = general somatic afferent |
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How does the optic nerve begin?
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-Axons of retinal ganglion cells form a nerve
-Nerve pierces sclera medial to posterior pole of eyeball |
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What covers the optic nerve?
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Meninges and CSF
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What hole does the optic nerve run through and where does it go?
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-Courses through optic canal of sphenoid bone
-Forms optic chiasm -Tracts terminate in lateral geniculate nucleus. |
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Where does the opthalmic nerve (V1) arise from?
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Sensory receptors which transmit info via peripheral processes.
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What hole does the opthalmic nerve course through, and where does it go after that?
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-Superior orbital fissure
-Through cavernous sinus to NCB's in trigeminal ganglion. |
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What happens to CN V1 (opthalmic) at the trigeminal ganglion?
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Its central nerve processes transmit sensation to 2 things: 1. Principle sensory nucleus
2. Spinal nucleus |
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what are the 3 very important branches of the opthalmic nerve?
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1. Lacrimal nerve
2. Frontal nerve 3. Nasociliary nerve |
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what are the 3 branches of the Frontal nerve (of CN V1)?
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1. Supratrochlear
2. Supraorbital 3. Nerve to the frontal sinus |
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What are the 5 branches of the Nasociliary nerve?
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1. Anterior/posterior ethmoidal nerves
2. Infratrochlear nerve 3. Meningeal nerve 4. Long ciliary nerves 5. Short ciliary nerves |
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What 3 nerves give motor innervation to the orbit?
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1. CN III - Oculomotor
2. CN IV - Trochlear 3. CN VI - Abducent |
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What type of functional modality are the 3 orbit motor nerves?
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General somatic efferent
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Where do the axons of CN III arise?
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From neurons in midbrain oculomotor nucleus
-Located near median plane, at the midbrain-pons junction. |
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What is the route of CN III in going from the oculomotor nucleus to the eye muscles?
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-Passes between posterior cerebral and superior cerebellar arteries
-Passes thru cavernous sinus -Thru Superior orbital fissure -Within common tendinous ring |
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What are the 2 divisions formed from the oculomotor nerve?
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1. Superior
2. Inferior |
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What is innervated by the Superior Oculomotor Nerve? (2 things)
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1. Levator Palpebrae superioris
2. Superior rectus |
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What is innervated by the Inferior Oculomotor Nerve? (3 things)
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1. Medial rectus
2. Inferior rectus 3. Inferior oblique |
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What does the trochlear nerve innervate?
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Superior oblique
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What is unique about the trochlear nerve?
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Axons originate from nuclei in the DORSAL brainstem surface.
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How does the trochlear nerve get to the orbit?
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Thru cavernous sinus, then thru Superior Orbital Fissure
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How does the Abducent nerve get to the orbit?
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Same way that the trochlear does, except from ventral brainstem side.
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What orbit structures receive autonomic innervation? Which get parasympathetic and which get sympathetic?
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Lacrimal gland = both
Sphincter pupillae - para Ciliary muscle - para Dilator pupillae = sympathetic Superior tarsal = sympathetic |
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What is the 2 neuron system like -For parasympathetic neurons?
-For sympathetic neurons? |
PARA: long preganglionic + short post-ganglionic neuron
SYMP: short preganglionic + long postganglionic neuron. |
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Where are the preganglionic parasympathetic NCBs for the lacrimal gland located?
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In the superior salivatory nucleus
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How do the preganglionic parasymp fibers for lacrimal gland get to it?
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-Emerge from brain w/ Nervous Intermedius (CN VII)
-Pass thru geniculate ganglion -Continue as Greater Petrosal -Join Deep Petrosal nerve |
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What do the Greater Petrosal + Deep Petrosal nerves combine to form?
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Nerve of the Pterygoid Canal
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Where do the preganglionic parasymp fibers for the lacrimal gland synapse?
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At the Pterygopalatine ganglion
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How do postganglionic parasymp fibers from the Pterygopalatine ganglion get to the Lacrimal gland?
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-Travel w/ Zygomaticotemporal nerve + Lacrimal nerve
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What happens once parasymp nerves get to the Lacrimal gland?
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They stimulate secretion.
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What happens when SYMPATHETIC nerves get to the lacrimal gland?
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They stimulate Vasoconstriction of blood vessels.
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Where are the preganglionic SYMPATHETIC NCB's for the lacrimal gland?
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In the lateral horn of the spinal cord gray matter - just like for all other sympathetic preganglionic neurons.
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Where do preganglionic sympathetic lacrimal fibers synapse?
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Superior Cervical Ganglion
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What structure is formed by postganglionic sympathetic lacrimal fibers?
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Internal Carotid nerve
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How does the internal carotid sympathetic nerve get to the lacrimal gland?
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Travels w/ Deep Petrosal nerve; Joins Greater Petrosal nerve;
Travels w/ Nerve of Pterygoid Canal |
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So how do both sympathetic AND parasympathetic postganglionic nerve fibers get to the lacrimal gland?
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By traveling with the Zygomaticotemporal and Lacrimal nerves.
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What type of innervation do Sphincter pupillae and ciliary muscles receive?
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Parasympathetic
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Where do preganglionic parasymp fibers for Sphinct. pupillae and ciliary muscles arise? How do they get where they're going?
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From Edinger-Westphal nucleus in midbrain; travel w/ CN III to the ciliary ganglion.
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What happens to parasymp preganglionic fibers at the ciliary ganglion?
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Synpase and send postganglionic fibers via SHORT CILIARY NERVES (V1 branches) to Sphincter pupillae and ciliary mm.
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What happens when the postganglionic parasymp fibers of Short Ciliary Nerves reach their muscles?
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-Pupil constriction
-Lens thickening (accommodation) |
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What type of innervation do Dilator pupillae and Superior tarsal muscles receive?
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Sympathetic
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Where do preganglionic symp fibers for Dilator pupillae and Superior tarsal muscles arise? How do they get where they're going?
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From spinal cord; enter the sympathetic trunk and synapse in Superior Cervical Ganglion.
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What happens to postganglionic sympathetic fibers for Dilator pupillae and Superior tarsal muscles?
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Form Internal Carotid nerve plexus; pass uninterrupted thru ciliary ganglion.
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What V1 branch carries sympathetic innervation to Dilator pupillae and Superior tarsal muscles after passing thru the ciliary ganglion?
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Long Ciliary nerves (V1)
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What happens when sympathic nerves stimulate Dilator pupillae and Superior tarsal muscles
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-Pupils widen
-Palpebral fissure widens all the way. |
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What are the 3 AXES of the eye?
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1. Vertical
2. Horizontal/transverse 3. Anteroposterior |
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What 3 actions occur around the vertical axis?
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1. Abduction
2. Neutral 3. Adduction |
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What 3 actions occur around the horizontal axis?
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1. Elevation
2. Neutral 3. Depression |
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What 3 actions occur around the anteroposterior axis?
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1. Extorsion
2. Neutral 3. Intorsion |
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What is extorsion?
What is intorsion? |
Extorsion: 12 o'clock on eye twists laterotemporally.
Intorsion: 12 o'clock on eye twists medionasally. |
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Levator palpebrae superioris:
-Innervation -Action |
Innervation: CN III
Action: raises the eyelid |
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Medial rectus:
-Innervation -Action around axes |
Innervation: CN III
Vertical axis: adduction Horizontal ax: nothing Antpost axis: nothing |
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Lateral rectus:
-Innervation -Action around axes |
Innervation: CN VI
Vertical axis: abduction Horizontal ax: nothing Antpost axis: nothing |
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Superior rectus:
-Innervation -Action around axes |
Innervation: CN III
Vertical axis: adduction(2') Horizontal ax: Elevation (1') Antpost axis: Intorsion (3') |
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Inferior rectus:
-Innervation -Action around axes |
Innervation: CN III
Vertical axis: adduction(2') Horizontal ax: Depression(1') Antpost axis: Extorsion (3') |
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Superior oblique
-Innervation -Action around axes |
Innervation: CN IV
Vertical axis: abduction Horizontal ax: Depression Antpost axis: Intorsion |
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Inferior oblique
-Innervation -Action around axes |
Innervation: CN III
Vertical axis: abduction Horizontal ax: Elevation Antpost axis: Extorsion |
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Why does SO cause depression around horizontal axis?
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Because it elevates the posterior aspect of the eye
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Why does IO cause elevation around the horizontal axis?
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Because it depresses the post aspect of eye.
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Which muscles achieve eye movement in the horizontal plane only?
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Medial and lateral rectus mm.
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What muscles achieve eye elevation or depression?
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Superior oblique
Inferior oblique Superior rectus Inferior rectus |
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What 2 conditions regarding the axis of gaze are achieved by eye ABDUCTION?
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1. Axis aligned w/ long axis of rectus muscles
2. Axis perpendicular to long axis of oblique muscles. |
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What is achieved by abducting the eye?
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-Rectus muscles are optimally positioned to elevate or depress
-Oblique muscle contribution is minimal |
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What 2 conditions regarding the axis of gaze are achieved by eye ADDUCTION?
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1. Axis perpendicular to long axis of rectus muscles
2. Axis aligned w/ long axis of oblique muscles |
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What is achieved by adducting the eye?
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-Rectus muscles contribute minimally
-Oblique muscles optimally positioned to elevate/depress |
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What mnemonic is useful for remembering what direction to tell the patient to look when testing extraocular muscles?
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O's toward the nose and upside down.
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What is a common clinical complaint seen in eye motor nerve injuries?
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Diplopia - double vision.
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What 2 general types of neural problems can cause diplopia?
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-Central lesions - in brainstem nuclei
-Peripheral lesions - injuries to the nerves. |
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What is ptosis?
What is lateral strabismus? |
Ptosis = drooping eyelid
Lat Strabismus = eye turning down and laterally |
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Damage to what nerve causes ptosis, and why?
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CN III - because the levator palpebrae superioris is paralyzed.
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Why does lateral strabismus occur in CN III damage?
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Medial rectus and Superior rectus muscles are paralysed; leaves LR6(SO)4 unopposed.
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What are 4 possible casues of CN III injury?
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-Intracranial aneurysm
-Trauma -Inflammation (syphilis, diabetic neuropathy) -Cavernous sinus thrombosis |
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What will a CN IV lesion result in?
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Inability to look down and nasally (depress/adduct)
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Why is depress/adduction inhibited by CN IV lesion?
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Superior Oblique is paralysed
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What is a clinical sign of CN IV injury?
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Head tilt - toward opposite side of eye injured
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Why do patients w/ injured CN IV tilt their head?
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Because the normal eye intorts, realigning the axis of gaze with the extorted injured eye.
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What are 2 common causes of CN IV injury?
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-Trauma
-Cavernous sinus thrombosis |
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What is a common sign of CN VI injury? Why?
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Medial strabismus - medial rectus m is unopposed b/c lateral rectus is paralyzed
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What is the most common cause of CN VI injury?
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Cavernous sinus thrombosis
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What nerve injury would result in a loss of lacrimation?
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CN VII - w/ greater petrosal nerve involved too.
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What nerve is associated with Horner's syndrome?
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CN III sympathetic fibers
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What are 4 symptoms of Horner's Syndrome?
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-Miosis (pupil constriction)
-Ptosis (drooping eyelids) -Anhydrosis (lack sweating) -Erythematosis (skin blushes) |
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What causes miosis in horner's syndrome?
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Dilator pupillae paralysis - unopposed sphincter pupillae
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What causes ptosis in horner's syndrome?
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Paralysis of superior tarsal m
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What causes anhydrosis in horner's syndrome?
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Loss of head/neck sweat gland innervation
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What causes erythematosis in horners syndrome?
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Blood vessel dilation
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What 2 conditions can result from CN III parasymp fiber lesion?
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-Loss of accommodation to light reflex
-Pupil dilation |
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Why do pupils dilate in CN III Parasymp fiber lesions?
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Sphincter pupillae muscles are paralysed so dilator pupillae m are unopposed.
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Why is accomodation to light reflex impaired by CN III lesion?
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B/c the ciliary m and sphincter m are paralyzed.
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