Orbit Anatomy

Question 1

What does the ophthalmic artery branch off from?

Answer 1

The internal carotid artery

Question 2

Throwback: where does the lacrimal duct drain?

Answer 2

The inferior meatus

Question 3

What does the sphincter pupillae do? Is it under parasympathetic or sympathetic control?

Answer 3

Constricts the pupil

It is under parasympathetic control (CN III)

Question 4

What are the lacrimal canaliculi?

Answer 4

Superior and inferior ducts that drains tears from the lacrimal papilla to the lacrimal sac

Question 5

What is this structure?

Answer 5

Superior rectus muscle

Question 6

What are the zonule fibers?

Answer 6

they anchor the lens to the ciliary body.

Question 7

The lateral rectus muscle is innervated by what cranial nerve?

Answer 7

Abducens, CN VI

Question 8

What artery in the eye is an anatomical end artery?

Answer 8

The central retinal artery

Question 9

What are the three branches of the ophthalmic nerve?

Answer 9

1. Frontal (further branches)
2. Nasociliary
3. Lacrimal

Question 10

What is this structure?

Answer 10

Frontal nerve

Question 11

What nerves are responsible for the corneal reflex?

Answer 11

Afferent/sensory: Nasociliary branch of V1

Motor: CN VII - Facial

Question 12

What four branches does the ophthalmic artery give off?

Answer 12

1. Lacrimal artery
2. Long and short ciliary arteries
3. Supraorbital artery
4. Supratrochlear

Question 13

What does the lens do?

Answer 13

it refracts light to focus it on the retina

Question 14

What innervates the superior oblique muscle?

Answer 14

CN IV - Trochlear

Question 15

What is the point of entry of the optic nerve into the retina called?

Answer 15

The optic disc

Question 16

What does the nasociliary nerve innervate?

Answer 16

The ethmoidal air cells

Question 17

How many layers is the retina?

Answer 17

10

Question 18

What does the dilator pupillae muscle do? Is it under parasympathetic or sympathetic control?

Answer 18

It increases the size of the pupil

It’s under sympathetic nervous system control

Question 19

What is the retina?

Answer 19

the neurosensory layer of the eye

Question 20

What is this structure?

Answer 20

optic nerve

Question 21

The superior oblique muscle is innervated by what cranial nerve?

Answer 21

Trochlear, CN IV

Question 22

Where does the ophthalmic division of the trigeminal nerve (V1) enter the orbit?

Answer 22

Superior orbital fissure

Question 23

What do the tarsal glands do?

Answer 23

They are responsible for the supply of meibum, an oily substance that prevents evaporation of the eye’s tear film

Question 24

Where do all four rectus muscles attach?

Answer 24

The fibrous Annulus Ring of Zinn (annulus tendinous)

Question 25

What is the macula?

Answer 25

An oval yellowish area surrounding the fovea

Question 26

What innervates the lateral rectus muscle?

Answer 26

CN VI - Abducens

Question 27

If the ciliary muscle is contracted, what are the zonular fibers doing? What is the effect on the lens and vision?

Answer 27

The zonular fibers are relaxed The lens is thicker so you can see closer up

Question 28

What innerveates the lacrimal gland?

Answer 28

CN VII - Facial

Question 29

If the ciliary muscle is relaxed, what are the zonular fibers doing? What is the effect on the lens and vision?

Answer 29

The zonule fibers will be contracted The lens is flattened so you can look at something far away

Question 30

What is the lamina papyracea? What bone is it part of?

Answer 30

A smooth, oblong, and very thin piece of bone that covers the middle and posterior ethmoidal cells and forms a large part of the medial wall of the orbit. It is part of the ethmoid bone

Question 31

What is this structure (tip of upper probe)?

Answer 31

The ciliary ganglion

Question 32

What muscle is responsible for blinking?

Answer 32

Levator palpabrae superioris

Question 33

Where is the abducens nerve found?

Answer 33

On the medial side of the lateral rectus muscle (which it innervates!)

Question 34

Where can you find CN IV in the orbit?

Answer 34

On top of the superior oblique muscle

Question 35

You cannot pronounce a person with this reflex brain dead

Answer 35

Corneal reflex

Question 36

What are the branches of the frontal nerve?

Answer 36

Supratrochlear nerve and the supraorbital nerve

Question 37

What is muscle is responsible for accomodation? What innervates that muscle?

Answer 37

Ciliary muscle Parasympathetics of CN III

Question 38

What is the venous drainage of the orbit? Where do these empty into?

Answer 38

Superior and inferior ophthalmic veins that drain into the cavernous sinus (then the superior petrosal sinus, sigmoid sinus, and finally the internal jugular vein)

Question 39

What is the ciliary ganglion?

Answer 39

a parasympathetic ganglion located just behind the eye in the posterior orbit. The oculomotor nerve coming into the ganglion contains preganglionic axons from the Edinger-Westphal nucleus (a part of the brainstem) which form synapses with the ciliary neurons. The postganglionic axons run in the short ciliary nerves and innervate two eye muscles: the sphincter pupillae & the ciliaris contracts

Question 40

What are the medial rectus, superior rectus, inferior rectus, and inferior oblique muscles innervated by?

Answer 40

CN III, occulomotor

Question 41

What structure is this?

Answer 41

levator palpebrae superioris muscle

Question 42

What muscle is responsible for each of these movements?

Answer 42

Question 43

What nerve palsy is this?

Answer 43

CN VI - Abducens nerve palsy There is unopposed pull by the medial rectus

Question 44

What is Horner's syndrome?

Answer 44

Drooping of the eyelid, lack of pupil dilation

Question 45

What does the lacrimal gland secrete?

Answer 45

Lacrimal fluid - a watery, saline solution containing lysozyme that moistens the surfaces of the conjunctiva and cornea

Question 46

What nerve palsy is this?

Answer 46

CN III - Occulomotor palsy Downward and outward gaze, dilated pupils and ptosis (drooping of upper eye lid)

Question 47

What is the area of most acute vision in the eye?

Answer 47

The fovea centralis

Question 48

What is this structure?

Answer 48

Lacrimal nerve

Question 49

Where are the palpebral and bulbar conjunctiva?

Answer 49

The bulbar conjunctiva is on the white portion of the eye The palpebral conjunctiva is on the inner surface of the eye Note: both innervated by V1

Question 50

What is the lacrimal caruncle?

Answer 50

the small, pink, globular nodule at the inner corner (the medial canthus) of the eye. It is made of skin covering sebaceous and sweat glands

Question 51

What is located in the center of the optic nerve?

Answer 51

The central retinal artery

Question 52

What is the corneal reflex?

Answer 52

Involuntary blinking of the eyelids elicted by stimulation of the cornea Stimulation should elict both a direct and indirect or consensual response from the other eye

Question 53

What is this structure?

Answer 53

Trochlear nerve

Question 54

What are the three layers of the eyeball?

Answer 54

1. Fibrous outer layer: 5/6 sclera, 1/6 cornea 2. Vascular layer: choroid, ciliary body & iris 3. Inner layer: retina (optic part + fovea centralis)

Question 55

What is this structure?

Answer 55

Supraorbital nerve

Question 56

What is this structure?

Answer 56

Trochlea

Question 57

What nerve palsy is this?

Answer 57

CN IV - Trochlear nerve palsy Unopposed pull of the superior rectus muscle

Question 58

What is the limbus?

Answer 58

The source of new cells to renew the cornea

Question 59

What is this structure?

Answer 59

Supratrochlear nerve

Question 60

What innervates the conjuctiva?

Answer 60

V1