Orbit, Anatomy

Front 1

Cause of double vision

Back 1

A blow to the eye, b/c this causes an increase in pressure within the eye. The medial wall & floor are very thin, so the contents of the orbit can sink into the maxillary sinus & cause double vision

Front 2

Exopthalmos

Back 2

Tumors of the orbit that produce bulging of the eye. Tumors in the sphenoid & posterior ethmoid sinuses are in close proximity to the optic nerve

Front 3

Eyelid Layers:

Back 3

1)external skin
2)muscular layer
3)tarso-facial layer
4)palpebral conjuctiva

Front 4

Nerves of the orbit? (in general)

Back 4

---3 motor nn. to its muscles (CN III, IV, VI) [LR6, SO4, AO3]
---sensory ophthalmic division of CN V
---optic nerve arises in the retina of the eye, the other nn. enter the orbit through the sup. orbital fissure

Front 5

What CNs provide sensory innervation to the eye?

Back 5

Optic Nerve (CN II)
Ophthalmic Nerve, From Trigeminal Nerve (V1)

Front 6

Name Source of Opthalmic Nerve and also its three branches

Back 6

From Trigeminal (V1)
-Frontal
-Nasocilliary
-Lacrimal

Front 7

What are the branches of the Nasocilliary Nerve? What type of nerves and what do they supply?

Back 7

The Nasociliary Nerve: sensory nerve to the eye, supplies several brs. to the orbit:
--ANTERIOR ETHMOIDAL N. - terminal br, supply mucous membrane of the sphenoidal and ethmoidal sinuses and the nasal cavities, and the dura of the ant. cranial fossa
--LONG CILIARY NN. - transmit AFFERENT fibers from the iris and cornea and some post-synaptic sympathetic fibers to dilator pupillae

Front 8

What does the LACRIMAL N supply? Arise from? Branch of? Work with?

Back 8

--Arises in lat wall of cavernous sinus, passes to the lacrimal gland
--Gives brs. to conjunctiva and skin of superior eyelid
--Branch of Ophthalmic, from Trigeminal (V1)
--provides secretomotor fibers from zygomatic n. (V2)

Front 9

Describe the frontal nerve

Back 9

--Br of Ophthalmic div of Trigeminal (V1)
--Divides into Supraorbital and Supratrochlear
--Supplies Upper Eyelide, Forehead and Scalp

Front 10

Describe the Oculomotor nerve (CNIII):
--Supplies what muscles??
--Innervation types??
--Nerve Components?
--Divisions??

Back 10

--Supplies most ocular mm muscles
--Innervation types & Nerve Components: supplies parasympathetic innervation to the sphincter pupillae m. of the iris and the ciliary m. of accommodation; it has 3 nerve components: somatic efferent (motor), general somatic afferent (to same mm), general visceral efferent (mm of iris and ciliary body with a synapse in the ciliary ganglion)
--Divisions:
1) Superior Division
2) Inferior Division

Front 11

Describe Trochlear N (CNIV) and its role in orbit

Back 11

--Smallest of CN's, supplies only one muscle - the sup. oblique
--Only CN that emerges from the dorsal aspect of the brainstem
--Most superior nerve entering in superior orbital fissure
--In orbit it is medial to frontal nerve

Front 12

Describe ABDUCENS N (CNVI) and its role in orbit

Back 12

--Supplies only ONE muscle: the lat. rectus m.
--Enters the cavernous sinus by piercing the dura mater on the dorsum sellae of the sphenoid bone, turning over a notch in the bone below the posterior clinoid process
--Passing forward within sinus on lateral side of internal carotid a., enters orbit through the lower potion of the superior orbital fissure
--At apex of orbit, passes between the two heads of origin of lateral rectus m., inferior to other nn. in this location

Front 13

Describe the AUTONOMIC INNERVATIONS of the ORBIT

Back 13

SYMPATHETIC/PARASYMPATHETIC
preganglionics from oculomotor (III)
cilliary ganglion: located between optic nerve and lat. rectus m, ~1cm from post limit of orbit; motor root from inf. br. of CN III, fibers contained in this root synapse in ciliary ganglion; the sensory root of ganglion is a br. of nasociliary n. of CN V1; the sympathetic root from the cavernous plexus passes to the ganglion adjacent to the sensory root; the nerve fibers of both the sensory and sympathetic roots pass through the ganglion WITHOUT synapsing; 6-10 short ciliary nn. leave ant. part of ganglion and course forward above and below optic nerve, to pierce the back of the eyeball
short ciliary - postganglionic parasympathetics to sphincter pupillae and ciliary muscles of eyeball, postganglionic sympathetics to dilator pupillae
postganglionic parasympathetics from pterygopalatine ganglion to lacrimal glands; preganglionics from facial, CN VII, via greater petrosal

Front 14

What make up the ORBIT bone?
What are its boundaries?

Back 14

Orbit: pyramidal-shaped space, formed by seven bones of the skull - four walls and an apex; space in between consists of the ethmoidal air cells and sphenoid sinus
ROOF - orbital plate of frontal bone, and near the apex, lesser wing of the sphenoid bone; concave, especially laterally where the lacrimal fossa accommodates the lacrimal gland;
LATERAL WALL -front: zygomatic bone, behind: greater wing of the sphenoid bone; separates the orbit from the temporal fossa

FLOOR -Orbital surface of maxilla, supp. laterally and anteriorly by the zygomatic bone and medially and posteriorly by the palatine bone
MEDIAL wall - frontal process of the maxilla, the lacrimal bone and the orbital lamina of the ethmoid bone, and a small part of the body of the sphenoid bone

Front 15

7 bones that make up the ORBIT

Back 15

1)FRONTAL- entire roof of orbit.

2)ETHMOID - a very delicate bone in medial wall of orbit.


3)MAXILLA- medial wall and much of floor. The anterior lacrimal crest is on the medial margin. (*relation with sphenoid bone, info below)


LACRIMAL - very small bone; gives a crest - posterior lacrimal crest; between the post. and ant. crests is the fossa for the lacrimal sac (not same as lacrimal fossa).

ZYGOMATIC - lateral margin and the rest of the floor


SPHENOID - forms apex; number of openings

PALATINE - small role in the floor of the orbit

Front 16

FORAMINA OF FRONTAL ORBIT

Back 16

3 prominent foramina: to know in this region -
1)SUPRAORBITAL NOTCH (superior margin)
2)& 3) ANTERIOR and POSTERIOR ETHMOID FORAMINA (at junction of frontal/ethmoid bones). Nerves and vessels pass FROM orbit to the nasal cavity through these foramina

Front 17

INFRAORBITAL GROOVE: where? what is in it?

Back 17

Infraorbital groove is a deep groove in the MAXILLA BONE on the orbital floor, where infraorbital n. lies.

Front 18

openings of SPHENOID:

Back 18

MEDIALLY:
--optic canal for optic n./ophthalmic a.
LATERALLY:
--Superior orbital fissure for nerves (III, IV, V1, VI) & superior ophthalmic v.;
---inferior orbital fissure: brs. of maxillary nerve and artery pass; veins from deep face region pass thru & connect with veins within orbit

Front 19

What runs thru the Superior orbital Fissure? What does it separate?

Back 19

NERVES:
CN III, IV, V1, VI
(Occulomotor, Trochlear, Trigeminal, Ophthalmic br, Spinal Accessory)
--Superior Ophthalmic Vein
--sympathetic fibers from cavernous plexus
--Separates the greater and lesser wings of SPHENOID

Front 20

What runs thru the INFERIOR ORBITAL FISSURE? where is it?

Back 20

--Brs. of maxillary nerve (Infraorbital & Zygomatic brs.) and artery pass
--Infraorbital nerve and artery,
--VEINS from deep face region pass thru & connect with veins within orbit
--Communication between inferior ophthalmic vein and pterygoid plexus
--Located between sphenoid and maxilla

Front 21

What are the principal openings of the ORBIT BONE region that lie at the junction of its walls? What do they transmit?

Back 21

Optic canal - roof and medial wall; transmits ophthalmic artery and optic nerve (covered by meninges)

Superior orbital fissure - transmits CN III, IV, V1, VI, sympathetic fibers from cavernous plexus, and superior ophthalmic vein

Inferior orbital fissure - accommodates structures which have only an indirect relation to orbit, i.e., infraorbital nerve and artery, communication between inferior ophthalmic vein and pterygoid plexus, and infraorbital & zygomatic brs. of V2

Front 22

What is in the Conjunctival Sac?

Back 22

--PALPEBRAL CONJUNCTIVA: lines the inside of the lid
--BULBAR CONJUNCTIVA: covers the eyeball
--FORNIX: reflection of the conjunctiva from the eyeball to the eyelid; a potential space filled with nothing but tears; the lacrimal gland secretes tears and they fill this sac; superior fornix directly receives tears from the lacrimal gland through small ducts that empty from the deep lobe of the gland

Front 23

Give summary of eyelid

Back 23

movable folds capable of closing in front of the eye, providing protection - upper lid is larger, more movable (due to having an elevator muscle - levator palpebrae superioris)
the eyelid is composed of five layers
skin: thin
subcutaneous tissue: lax, scanty, rarely contains fat; anterior edge of lid are cilia (eyelashes); cutaneous nn. of eyelid = brs of V1 and brs. of infraorbital br. of V2; rich vascular supply
muscular layer: mostly palpebral portion of orbicularis oculi m, arises from med palb lig
tarsofascial layer: an important plane of division in the eyelid between a superficial zone continuous with subcutaneous tissues of face/scalp and a deeper area continuous with space of the orbit; this layer consists of:
tarsus: dense fibrous plate; embedded within are the tarsal glands
orbital septum: membrane
conjunctiva: lines inner surface of each eyelid (palpebral) and is reflected over the anterior portion of the sclera and cornea of the eyeball as the bulbar conjunctiva

Front 24

Cavernous Sinuses

Back 24

lie on either side of body of sphenoid, extend from sup. orbital fissure (in front) to the apex of petrous portion of temporal bone (in back); formed between the meningeal and periosteal layers of dura and trabeculae from each layer cross space, giving it a reticular (cavernous) structure

Front 25

Anterior cranial fossa:

Back 25

limited behind by post borders of lesser wings of sphenoid and groove for optic chiasma; floor is formed by orbital plates of frontal bone, cribriform plate of ethmoid and lesser wings and fore part of body of sphenoid; anterior midline is the crest of frontal bone leading to the foramen cecum, through which emissary vein passes from nasal cavity to beginning of sup. sagittal sinus

Front 26

superior ophthalmic v.:

Back 26

begins in nasofrontal vein, enters orbit through supraorbital foramen (notch), after communicating with supraorbital vein; has tributaries which correspond to upper branches of ophthalmic a, usually joined by inf. ophthalmic vein at medial end of sup. orbital fissure; may leave head between two head of lat. rectus or above the muscular cone; ends in cavernous sinus; DOES NOT CONTAIN VALVES.

Front 27

What is the flow of lacrimal fluid across the eye?

Back 27

Tears secreted from the lacrimal gland moves across eye via blinking, toward the medial canthus and lacrimal lake; drained off by lacrimal canaliculi; empty into lacrimal sac, then pass through nasolacrimal duct to inferior meatus of nasal cavity

Front 28

What muscles does the trochlear n. (CN IV) supply?

Back 28

Trochlear nerve innervates superior oblique muscle, which acts around a trochlea or pulley.

Front 29

What is the innervation to the two heads of the lateral rectus m.?

Back 29

Abducens nerve (CN VI).

Front 30

What are the relations of oculomotor and nasociliary nn. to optic n. and ciliary ganglion?

Back 30

--The inferior division of the oculomotor nerve sends a short MOTOR ROOT up to the ciliary ganglion, which lies lateral to the optic nerve. The inferior division then passes anteriorly along the lateral edge of the inferior rectus.
--Nasociliary sends a branch to reach ciliary ganglion and then passes anteromedially superior to the optic nerve.

Front 31

What does the superior ophthalmic v. drain into?

Back 31

Cavernous sinus through the superior orbital fissure.

Front 32

Define short ciliary nn. from ciliary ganglion to bulb.

Back 32

Short ciliary nerves carry postganglionic parasympathetics and sympathetics and sensory fibers from the ciliary ganglion to the back of the eyeball.

Front 33

What are the actions of extraocular mm?

Back 33

Superior oblique - turns pupil down and out (abducts & depresses)
Inferior oblique - up and out
Superior rectus - up and in
Inferior rectus - down and in
Medial rectus - in
Lateral rectus - out

Front 34

What do sympathetic nerves do to the eye?

Back 34

Sympathetic nerves allow the eye to dilate--if you blocked these nerves, the eye would constrict. A sympathetic blocker would also cause ptosis--it would paralyze the superior tarsal muscle, which holds the lids up involuntarily and receives sympathetic innervation.

Front 35

Horner's syndrome

Back 35

a disease characterized by a loss of sympathetic innervation to the head and neck.

Front 36

You are testing the extraocular muscles and their innervation in a patient who periodically experiences double vision. When you ask him to turn his right eye inward toward his nose and look downward he is able to look inward, but not down. Which nerve is most likely involved?

Back 36

the patient has the eye turned inward, so the doctor must be testing the oblique muscles. The superior oblique muscle is the muscle that lowers the eye when it is turned inward. Since the patient can't do this, the superior oblique must not be functioning, and this muscle is innervated by the trochlear nerve.

Front 37

The outermost layer of the optic nerve sheath is a continuation of the?

Back 37

The optic nerve comes off the base of the brain and passes through the optic canal. As it leaves the brain, it still retains all of the meningeal layer coverings. So, it is covered by meningeal dura, arachnoid membrane, and pia mater.

Front 38

an increase in intracranial pressure will increase the pressure in the? What will this do?

Back 38

subarachnoid space
--This may squeeze the optic nerve and make the optic nerve bulge into the eye, a condition known as papilledema.

Front 39

The inner lining of the eyelid is called the:

Back 39

Palpebral Conjunctiva!
--A thin membrane that lines the eyelid; continuous with the bulbar conjunctiva which lines the eyeball.

Front 40

You are examining a patient who has a pituitary tumor involving the cavernous sinus. While doing a preliminary eye exam, you suspect the right abducens nerve of the patient has been damaged by the tumor. In which direction would you have the patient turn his right eye to confirm the defect?

Back 40

OUTWARD;
Since the lesion appears to be in the abducens, which innervates the lateral rectus muscle, ask the patient to turn the eye outward. If the patient could not do this, it would confirm that there was a lesion in the abducens nerve, since the muscle responsible for lateral movement of the eye would be paralyzed.

Front 41

a tumor in the cavernous sinus could affect many nerves. Name them.

Back 41

The oculomotor nerve (CN III), trochlear (CN IV), ophthalmic division of trigeminal (CN V1), and abducens (CN VI) all pass through the cavernous sinus.

Front 42

You have a patient with a drooping right eyelid. You suspect Horner's syndrome. Which signs on the right side would confirm this diagnosis?

A. Constricted pupil
B. Dry eye (lack of tears)
C. Exophthalmos
D. Pale, blanched face
E. Sweaty face

Back 42

A. Constricted pupil:

Horner's syndrome is a disorder involving damage to the sympathetic trunk in the neck. This means that the sympathetics of the head will be disrupted. This causes a variety of very characteristic symptoms, including a constricted pupil. Remember--sympathetic nerves innervate the dilator pupillae muscle. This muscle allows the eye to dilate. If these sympathetic nerves are lost, the pupil will contract.

Front 43

Following endarterectomy on the right common carotid, a patient is found to be blind in the right eye. It appears that a small thrombus embolized during surgery and lodged in the artery supplying the optic nerve. What artery would be blocked?
A. Central artery of the retina
B. Infraorbital
C. Lacrimal
D. Nasociliary
E. Supraorbital

Back 43

A. CENTRAL ARTERY of RETINA:
--branch of the ophthalmic artery.
-- sole blood supply to the retina
--no significant collateral circulation and blockage of this vessel leads to blindness

Front 44

You are asked to check the integrity of the trochlear nerve in the right eye of a patient. Starting with the eyes directed straight ahead, you would have the patient look:

Back 44

The Superior Oblique is innervated by the Trochlear Nerve (CNIV); this muscle moves the eye DOWNWARD when the patient is instructed to look inwards towards the nose, and then DOWN.

Front 45

An adolescent boy suffers from severe acne. As is often the case he frequently squeezed the pimples on his face. He subsequently develops a fever and deteriorates into a confused mental state and drowsiness. He is taken to his physician and after several tests a diagnosis of cavernous sinus infection and thrombosis is made. The route of entry to the cavernous sinus from the face was most likely the ???

Back 45

OPTHALMIC VEINS
--Are continuous with the facial vein and the pterygoid plexus of veins
--Drain the face toward the cavernous sinus.
--valveless, so infections from the face can drain into the cavernous sinus.

Front 46

During a physical examination it is noted that a patient has ptosis. What muscle must be paralyzed?

Back 46

The superior tarsal muscle is a smooth muscle which is sympathetically innervated. It is an involuntary muscle that elevates the eyelid. It is innervated by the cervical sympathetic trunk, and this muscle's functioning provides a good indication of the integrity of the cervical sympathetic trunk. If the cervical sympathetic trunk has been damaged, a patient will have ptosis, a droopy eyelid.

Front 47

Ptosis

Back 47

A droopy eyelid; due to damage in the sympathetically innervated superior tarsal muscle, smooth muscle which elevates the eyelid. It is innervated by the cervical sympathetic trunk, and this muscle's functioning provides a good indication of the integrity of the cervical sympathetic trunk.

Front 48

Starting from a position gazing straight ahead, to direct the gaze downward, the inferior rectus muscle must be active along with the: ???
Innervated By???

Back 48

, to direct the gaze downward, you want to find a muscle that will depress the eye while counterbalancing the medial rotation with lateral rotation. And, the superior oblique, innervated by the trochlear nerve (CN IV), does just that--it depresses the eye while laterally rotating it. The inferior oblique muscle laterally rotates the eye and elevates the eye.