Anatomy, Block 2: Lecture 6: Orbit

Front 1

ID the nerves and vessels shown here.

Which CN is the internal carotid inferior to?

Back 1

The internal carotid is directly inferior to the Optic n. (CN II).

Front 2

What are the 3 branches of the Trigeminal n (CN V)?

Where do they exit?

"Standing Room Only"

Back 2

Branches

CN V1: Opthalmic - Superior orbital fissure

CN V2: Maxillary - Foramen rotundum

CN V3: Mandibular - Foramen ovale

Front 3

ID the cavernous sinus.

Name the nerves and vessels that pass through.

Back 3

Cavernous sinus is located lateral to sella turcica (where pituitary gland sits), in middle cranial fossa.

Contains:

Eye nerves and internal carotid a.

- 1st 2 branches of CN V

*CN V1 (Opthalmic)

*CN V2 (Maxillary)

- CN III (Oculomotor)

- CN IV (Trochlear)

- CN VI (Abducens)

- Internal carotid a.

Front 4

What are the four parts of the internal carotid artery?

Which one branches?

Which one is directly inferior to the Oculomotor n. (CN III)?

Back 4

Only the cerebral part of the Int. Carotid a. branches.

Cavernous part is directly inferior to CN III. Both are in the cavernous sinus.

Front 5

Describe the branching pattern of CN V1 (Opthalmic) to the superior orbit.

Which arteries follow its branches?

Back 5

1. Opthalmic n (CN V1) exits Superior orbital fissure.

2. CN V1 -> Frontal n.

3. Frontal n. -> 2 parts

-> Supratrochlear (medial)

-> Supra-orbital (lateral)

NEED TO DO ARTERIES.

Front 6

ID the bones that form the orbit (eye socket).

What are the boundaries?

Back 6

Boundaries

Roof – frontal

Floor –

maxillary, zygomatic

Medial wall – ethmoid, lacrimal

Lateral wall – zygomatic

Apex – sphenoid

Front 7

ID the features of the eye.

Back 7

1) Supraorbital foramen - above the rim of orbit

2) (Lat -> med)

Ant, posterior ethmoid foramina

- Border of frontal and ethmoid

3) Nasolacrimal duct

- Lacrimal -> nasal

*Move laterally; sphenoid region

4) Optic canal

- Sphenoid

- Exit site for CN II

5) Superior orbital fissure

- Sphenoid -> ethmoid, palatine

6) Inferior orbital fissure

- Sphenoid -> maxillary

*Inf orbital fissure

goes postero-med to maxillary to make:

7) Infraorbital groove and canal

- Maxillary

*Infraorbital groove and canal end in...

8) Infraorbital foramen

*Post edge of orbit

- Maxillary

Front 8

Which bones make up these features?

Back 8

1) Supraorbital foramen - above the rim of orbit

2) (Lat -> med)

Ant, posterior ethmoid foramina

- Border of frontal and ethmoid

3) Nasolacrimal duct

- Lacrimal -> nasal

*Move laterally; sphenoid region

4) Optic canal

- Sphenoid

- Exit site for CN II

5) Superior orbital fissure

- Sphenoid -> ethmoid, palatine

6) Inferior orbital fissure

- Sphenoid -> maxillary

*Inf orbital fissure

goes postero-med to maxillary to make:

7) Infraorbital groove and canal

- Maxillary

*Infraorbital groove and canal end in...

8) Infraorbital foramen

*Post edge of orbit

- Maxillary

Front 9

What are the contents of the orbit?

Back 9

Fat

Eyeball

Muscles

a. Extraocular - extrinsic, move eye(ball)

b. Intraocular - intrinsic, ctrl lens and pupil

Opthalmic artery

*Branch of Internal carotid a.

Superior, inferior opthalmic veins

CNs:

II (Optic)

III (Oculomotor)

IV (Trochlear)

V (Trigeminal) - V1 (Opthalmic) and V2 (Maxillary) branches only

VI (Abducens)

Front 10

What are the CNs going to the orbit?

How do they reach the orbit?

Which CN branches further?

Name its 3 major branches.

How do they relate (e.g. sup./inf.)to each other?

Back 10

CNs to orbit

CN II - Optic

CN III - Oculomotor

CN IV - Trochlear

CN V - Trigeminal

- V1 (Opthalmic), V2 (Maxillary)

CN VI - Abducens

*CN II goes thru optic canal to reach orbit

All others go through Superior orbital fissure

CN V1 branches more, near sup. orbital fissure:

"LFN"

*Superficial

Lacrimal (more lateral)

Frontal

**Deep

Nasociliary

Front 11

What are the movements of the eyeball?

ABduct/ADduct

Depression/Elevation

Intorsion/Extorsion

Back 11

1. ABduct/ADduct

- pupil away/twd nose

2. Depress/Elevate

- Pupil down/up

3. Intort/extort

(= Med/lat rotation)

- Sup eye twd/away from nose

Front 12

Name the 7 extraocular muscles.

"L1, O2, R4"

Back 12

L1: Levator palpebrae superioris

O2:

Superior oblique

Inferior oblique

R4:

Superior rectus

Inferior rectus

Medial rectus

Lateral rectus

Front 13

What are the functions of the 7 extraocular muscles?

"L1, O2, R4"

"Inferiors extort"

"Recti Return" - except Lateral

Back 13

L1:

Levator palpebrae superioris - raise sup. eyelid

O2:

Superior oblique - ABduct, depress, intort (medially rotate) eyeball

Inferior oblique - ABduct, elevate, extort (= laterally rotate) eyeball

R4: "Recti Return" (all ADduct eyeball)

*All from common tendinous ring (near optic canal/sup. orbital fissure)

Superior rectus - ADduct, elevate, intort eyeball

Inferior rectus - ADduct, depress, extort eyeball

Medial rectus - ADduct eyeball

*Exception: Lateral rectus ABducts eyeball

Lateral rectus - ABduct eyeball

Front 14

Innervations of extraocular muscles

"SALT ME DOWN"

Back 14

"SALT ME DOWN"

Six ABducts Laterally, Trochlear acts Medially Down. Oculomotor n. does everything else.

I.e.,

CN VI (Abducens) ABducts eye by innervating Lateral rectus.

Trochlear (CN IV) Depresses eye, when its medially ABducted

--> innervates Superior Oblique, which:

Medially rotates (= Intorts), ABducts, and Depresses eyeball

Oculomotor (CN III) does everything else, i.e.

1) Levator palpebrae superior (sup. layer)

-> raise superior eyelid

2) Rectus muscles (R4) - "return" (ADduct)

- Superior rectus - ADducts, elevates, intorts

- Inferior rectus - ADduct, depress, extort

- Medial rectus - ADduct

- Lateral rectus - ABduct

Front 15

Name muscles shown here.

Hint: superficial eye.

What are their:

1) Functions

2) Innervations

"SALT ME DOWN"

"Recti Return"

"Inferiors Extort"

Back 15

"SALT ME DOWN"

Six ABducts Laterally, Trochlear acts Medially Down. Oculomotor n. does everything else.

I.e.,

CN VI (Abducens) ABducts eye by innervating Lateral rectus.

Trochlear (CN IV) Depresses eye, when its medially ABducted

--> innervates Superior Oblique, which:

Medially rotates (= Intorts), ABducts, and Depresses eyeball

Oculomotor (CN III) does everything else, i.e.

1) Levator palpebrae superior (sup. layer)

-> raise superior eyelid

2) Rectus muscles (R4) - "return" (ADduct)

- Superior rectus - ADducts, elevates, intorts

- Inferior rectus - ADduct, depress, extort

- Medial rectus - ADduct

- Lateral rectus - ADduct

Front 16

Which artery is the major supply of the orbit?

*Hint: it originates between thyroid and hyoid, in a region of the anterior triangle of the neck.

Name its branches.

Which are superficial and which are deep?

Back 16

Internal carotid -> Opthalmic a. ->

1) Superficial (lat -> medial)

- Lacrimal

- Supra-orbital

- Supratrochlear (next to Trochlear n, CN IV)

2) Deep (lat -> medial)

- Long ciliary a. ("go aLong to eyeball")

- Short ciliary a. ("short-circuits"; goes to ciliary ganglion)

- Central a. of the retina**

**Only a. for retina -> if cut off, you go blind

- Ethmoidal arteries (anterior, posterior)

**Ethmoid air cells (=air sinuses)

Front 17

Name the arteries shown here.

Which major artery do they originate from?

Is this from the superficial or deep eye?

Back 17

Internal carotid a.

-> Opthalmic (O)

Opthalmic a.

-> Lacrimal (lateral)

-> Supra-orbital (med)

-> Supratrochlear (most med; near Trochlear n., CN IV)

Superficial portion

Front 18

Name the arteries shown here.

Which major artery do they originate from?

Is this from the superficial or deep eye

Back 18

DEEP part of eyeball.

Internal carotid a. -> Opthalmic

*Lat -> Med

-> Long ciliary (-> "aLong to eyebaLL")

-> Short ciliary (-> "short-circuit" to ciliary ganglion)

-> Central a. of retina (-> only blood supply to retina; cut off -> blindness)

-> Ethmoid a. (ant, posterior) (-> ethmoid air cells (sinuses)

Front 19

Is this superficial or deep?

Name the nerves shown here.

Which are sensory and which do motor?

Back 19

Superficial

CN II = Optic n. (going thru optic canal)

CN IV = Trochlear n. (motor to sup. oblique)

CN V (Trigeminal) -> CN V1 (Opthalmic) ->

**Lat. -> medial

1) Lacrimal n. (LN) - sensory to skin of eyelid

2) Frontal n. (FN) - sensory to scalp, forehead, sup. eyelid

-> Supra-orbital (SON; lat.), Supratrochlear (STN; med)

Front 20

Is this superficial or deep?

Name the nerves shown here.

Which are sensory and which do motor?

Back 20

Deep

CN II: Optic

CN III: Oculomotor

CN V -> CN V1 (Opthalmic n.) ->

*Superficial branches:

Lacrimal, Frontal

**Deep branch:

Nasociliary n. (NCN;

Sensory to eyeball)

-> Infratrochlear

(eyelids, nose)

-> Ant., post. ethmoid nerves

(sensory to ethmoid, nasal region)

Front 21

Describe the innervation of the Extraocular muscles.

- GSE innervation ("LR6SO4AO3")

- GVE innervation (postsynaptic sympathetic)

- GA innervation

Is there parasympathetic innervation?

Back 21

**NO PARASYMPATHETIC INNERVATION

GSE innervation

(-> skeletal muscle of myotome origin)

LR6 - Lateral Rectus = CN VI (Abducens)

Sup. oblique - CN IV (Trochlear)

All Others - CN III (Oculomotor)

GVE innervation

- Postsynaptic sympathetic

* Levator palpebrae superioris (smooth muscle part)

*Blood vessels supplying extraocular muscles

GA innervation

- Proprioception, by CN V

Front 22

Where is the ciliary ganglion?

Back 22

Ciliary ganglion (CG) - deep orbit, between Optic n. (CN II) and Lacrimal N. (branch of CN V1)

Front 23

What are the intraocular muscles of the eye?

Which part of the eye is avascular?

Are they smooth or skeletal muscle?

What is their function?

Which are parasympathetic and which are sympathetic?

Back 23

Cornea = avascular

Intraocular muscles

- All smooth muscle

- Change lens or pupil

Lens

- Ciliary muscle

Accomodation: Contract -> change lens shape -> focus the eye

Pupil (size)

- Sphincter pupillae

(contract* pupil)

*Sphincter - "small"

- Dilator pupillae

(dilate pupil)

**Dilator - "double" (larger size)

Parasympathetic

Ciliary m.

Sphincter pupillae

Sympathetic

Dilator Pupillae

"Fight or flight" -> "Eyes widen in fear"

Front 24

What structure is shown here?

Which nerves provide its fibers?

Does it do somatic or autonomic?

Which nerves are alongside, but not part of it?

Back 24

Ciliary ganglion (CG), one of the 4 PSGs (parasymp. ganglia, in head).

Autonomic innervation (has symp., parasymp. fibers).

Nerves:

- Nasociliary (deep branch of CN V1)

= sensory

Nasociliary n. (NCN)

-> Long ciliary n. (alongside CG; goes aLong to eyeball)

-> Short ciliary n.

*Arises from CG

*Nerve combo:

- NCN - sensory

- CN III - parasymp.

- Symp. (piggyback on Opthalmic a.)

Front 25

What structure is shown here?

Which nerve gives general afferent (GA) innervation?

For General Visceral Efferent (GVE) innervation:

- Nerves for

a) Parasympathetic

b) Sympathetic

Which intraocular muscles get each?

Back 25

Key for GVE:

- Solid purple = presyn. parasymp.

- Dotted purple = postsyn. parasymp.

- Green = postsyn. sympathetic

Ciliary Ganglion (CG)

GA: Nasociliary n.

(= deep branch of CN V1, Opthalmic)

GVE

1) Sympathetic - to Dilator Pupillae

- Piggyback on Opthalmic a. AND

branches of CN V1 (Long ciliary n., short ciliary n.)

2) Parasympathetic - to Ciliary m. and Sphincter pupillae

- CN III: Presyn. para

-> synapse in CG

- Post-syn para exits CG to go to eyeball

Front 26

What is Horner's Syndrome?

How can you tell which part of the autonomic NS (parasymp vs. symp) is disrupted?

Back 26

Horner's syndrome:

1) Interrupt sympathetic innervation to head*

*E.g., damage T1-L2 (source of presyn. symp. neurons), sympathetic chain, cervical ganglia

2) Symp. NS -> dilator pupillae muscle, so:

- Patient can't dilate their pupil

3) Symptoms*

- Ptosis (droopy eyelids)

- Miosis (constricted pupil - since can't dilate)

*Seen on side contralateral to damaged site

- Anhydrosis (decreased sweating)

**Sympathetic makes you Sweaty

- Flushed skin

*If parasympathetic NS was interrupted, you'd see ptosis too...but NO miosis (since parasymp constricts pupil).

Instead you'd see dilated pupil.

Front 27

Which muscles form the Common Tendinous Ring* (CTR)?

*A "Rectus Ring"

What does the CTR divide?

What canal is inside it?

Back 27

"Rectus Ring"

- Sup., Inf, Medial, and Lateral Rectus form the Common Tendinous Ring

(= on Apex of Orbit)

CTR divides the Superior Orbital Fissure.

Optic canal is inside.

Front 28

ID this ring.

Which structures are superficial (outside) of it?

Which are deep/inside of it?

Back 28

Common tendinous ring, formed from the (4) Rectus muscles.

Superficial structures:

- Branches of CN V1: Frontal n. (FN), Lacrimal n. (LN)

- CN IV (Trochlear)

- Superior opthalmic vein (SO)

Deep

- CN III (Oculomotor - Sup., inf. parts)

- Nasociliary n. (NCN;branch of CN V1)

- CN VI (Abducens)

- Inferior Opthalmic v. (IOV)

Front 29

Eye exam

How to test function of

Inf. oblique?

Sup. oblique?

Back 29

Problem

Rectus and Oblique muscles overlap in function:

- Sup. rectus, inf. oblique = elevate eyeball

- Inf. rectus, sup. oblique = depress eyeball

"Rectus Returns" - Rectus muscles ADduct eye

"Oblique is Off to the Side" - Oblique muscles ABduct eye

So to test Oblique function only, have pt ADduct eye (pupil twds nose), and then...

a) Elevate eye (look up) -> Inferior oblique OK

b) Depress eye (look down) -> Superior Oblique OK

Front 30

Eye exam

How to test function of

Sup. rectus?

Inf. rectus?

Back 30

Problem

Rectus and Oblique muscles overlap in function:

- Sup. rectus, inf. oblique = elevate eyeball

- Inf. rectus, sup. oblique = depress eyeball

"Rectus Returns" - Rectus muscles ADduct eye

**Except Lateral Rectus!! (ABducts)

"Oblique is Off to the Side" - Oblique muscles ABduct eye

So to test Rectus function only, have pt ABduct eye (pupil twds nose), and then...

a) Elevate eye (look up) -> Sup Rectus OK

b) Depress eye (look down) -> Inf Rectus OK

Front 31

Which TWO muscles are needed to...

1) Look up?

2) Look down?

Back 31

1) Look up = elevation

-> Inferior oblique AND Superior rectus

2) Look down = depression

-> Superior oblique AND inferior rectus

Front 32

What innervates the lacrimal gland?

How do tears travel from the lacrimal gland?

What is the function of tears?

Back 32

Lacrimal gland = innervated by Facial n. (CN VII).

Path of tears:

*Goes lat -> medial

1) Lacrimal gland (makes tears)

2) Lacrimal puncta

3) Lacrimal canaliculi

4) Lacrimal sac (LS)

5) Nasolacrimal Duct (ND) to Inferior Meatus (IM) - nasal cavity

6) Inferior concha (IC; in nasal cavity)

Tears give nutrients and O2 to cornea, which is avascular (i.e., "Tears Take blood's place")