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SHB Exam 2 > The Orbit > Flashcards

The Orbit Flashcards

1
Q

What bones make up the outer orbit?

A

The frontal, maxillary, and zygomatic bones

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2
Q

What bones form the inside of the orbit?

A

Lacrimal bone
Ethmoid bone - medial wall
Greater & lesser wings of sphenoid bone
Palatine bone
The frontal bone forms the roof.
Maxillary bone forms a large part of the floor of the orbit.

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3
Q

What are the 7 layers of the eyelid (palpebrae) outer to inner?

A

SSMSTTP

Skin
Subcutaneous connective tissue
Muscular layer
Submuscular layer
Tarsal plate
Tarsal glands
Palpebral conjunctiva
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4
Q

What is Horner’s syndrome and its symptoms?

A

Lesion to the superior cervical sympathetic ganglion, with resulting paralysis in the Tarsal muscle on the affected side.

Ptosis (drooping eyelid)
Meiosis (small pupil)
Anhydrosis (lack of sweating)
Reddening of skin on affected side

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5
Q

What is the direction of tear flow?

A

Tears flow from a superiolaterally placed lacrimal gland to the medial canthus of the eye.

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6
Q

What are the structures that drain tears?

A

Puncta lacrimali - drain opening (2)
Lacrimal canaliculus - duct (2)
Lacrimal sac - collection of fluid
Nasolacrimal duct - drainage to nasal sinus

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7
Q

Describe parasympathetic innervation of the lacrimal gland.

A

The greater petrosal nerve branches from the facial nerve, travels through the middle ear and combines with the deep petrosal nerve (sympathetic fibers) to form the Vidian nerve of the pterygoid canal. The Vidian nerve synapses at the pterygoid ganglion (associated with the maxillary division of CN V).

From the maxillary nerve, the postganglionic parasympathetics & sympathetics travel along the zygomatic nerve (V2) to join the lacrimal branch of V1 and follow it to the lacrimal gland

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8
Q

Parasympathetic stimulation of the lacrimal gland __________ lacrimal secretion.

A

Parasympathetic stimulation of the lacrimal increases lacrimal secretion (tearing).

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9
Q

Sympathetic stimulation of the lacrimal gland results in _____________ and _____________ tear production.

A

Sympathetic stimulation of the lacrimal results in vasoconstriction and decreases tear production.

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10
Q

What are the recti muscles of the eye?

A

Superior Rectus

Inferior Rectus

Medial Rectus

Lateral Rectus

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11
Q

What is the origin of the recti muscles of the eye?

A

Anulus tendineus (fibrous ring around the optic nerve)

Anulus tendineus (fibrous ring around the optic nerve)

Anulus tendineus (fibrous ring around the optic nerve)

Anulus tendineus (fibrous ring around the optic nerve)

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12
Q

What innervates the recti muscles of the eye?

A

Superior, medial, and lateral recti done by CN 3 - AO 3 - Oculomotor Nerve (CN III)

Lateral rectus is done by 6 - LR6 - Abducent Nerve (CN VI)

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13
Q

What is the action of the superior rectus?

A

Moves the eye superiorly and medially (adduction)

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14
Q

What is the action of the inferior rectus?

A

Moves the eye inferiorly as well as medially (adduction)

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15
Q

What is the action of the medial rectus?

A

Moves the eye medially (adduction)

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16
Q

What is the action of the lateral rectus?

A

Moves the eye laterally (abduction)

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17
Q

Origin of the superior oblique?

A

Sphenoid bone

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18
Q

Route of insertion of the superior oblique?

A

Passes anteriorly through the middle/top of the orbit, hooks around the trochlea (pulley), continues the superior rectus muscle to insert onto the upper eye.

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19
Q

Innervation of the superior oblique?

A

SO4 - Trochlear nerve (IV)

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20
Q

Action of the superior oblique?

A

“IO, UO, SO, DO”

Moves the eye inferiorly and laterally (abduction)

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21
Q

Origin of the inferior oblique?

A

Maxilla

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22
Q

Route of insertion of the inferior oblique?

A

Runs laterally and underneath (inferior to) the inferior rectus muscle to insert onto the the inferior part of the eye.

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23
Q

Innervation of the inferior oblique?

A

AO 3 - Oculomotor Nerve (CN III)

24
Q

Action of the inferior oblique?

A

“IO, UO, SO, DO”

Moves the eye superiorly and laterally (abduction)

25
Q

Origin of the Levator Palpebrae Superioris?

A

Sphenoid

26
Q

Insertion of the Levator Palpebrae Superioris?

A

Tarsal plate

27
Q

Innervation of the Levator Palpebrae Superioris?

A

AO3 - Oculomotor Nerve (CN III)

28
Q

Action of the Levator Palpebrae Superioris?

A

Elevates/opens the upper eyelid

29
Q

How do the nerves of the eye enter the orbit?

A

CN3, CN 6, CN 4 all enter the orbit through the superior orbital fissure.

30
Q

What are the 3 main sensory branches of the ophthalmic nerve?

A

Lacrimal nerve - most lateral nerve AND artery in the orbit are the lacrimal nerve and artery

Frontal nerve - Runs along the roof of the orbit on top of the levator palpebrae superioris muscle.

Nasociliary nerve - crosses above the optic nerve from lateral to medial

31
Q

What are the branches and functions of the frontal nerve?

A

Supratrochlear nerve (which supplies sensory innervation to the skin above the medial canthus and a portion of the scalp) and lies more medial

Supraorbital nerve which supplies the superior palpebra and the scalp above and lies more lateral

32
Q

What are the branches and functions of the Nasociliary nerve?

A

Communicating branch to the ciliary ganglion – (CN 3 hops on V1)

Long ciliary nerves - sensory innervation to the eye (cornea, sclera, ciliary body).

Posterior ethmoidal nerve - to the posterior and middle ethmoidal air cells on the medial wall of the orbit.

Anterior ethmoidal nerve - to the middle and anterior ethmoidal air cells. (This nerve ends as the external nasal nerve, which supplies the external nose.)

Infratrochlear nerve - terminal branch of the nasociliary nerve that supplies the medial canthus, lower eyelid, and surrounding region of the orbit.

33
Q

Describe parasympathetic innervation to the eye through the ciliary ganglion.

A

Oculomotor (CN III) PNS fibers travel through the superior orbital fissure to synapse in the ciliary ganglion behind the orbit. The PS fibers follow the inferior division of the oculomotor nerve

From the ciliary ganglion, the postganglionic parasympathetic nerve fibers leave via short ciliary fibers and pass into the nasociliary nerve (from CN V1). The short ciliary nerves provide parasympathetic innervation of the orbit to cause constriction of the pupil (sphincter pupillae m.) and allow the eye to focus on near objects (contraction of the ciliary muscle).

34
Q

Sympathetic innervation to the eye through the ciliary ganglion.

A

Sympathetic fibers reach the eye via long ciliary nerves to innervate the dilator pupillae muscle (dilate pupil).

35
Q

What are the branched and supply of the ophtalmic artery?

A

Lacrimal

Central retinal

Long and short ciliary - to the choroid layer of the eye.

Supraorbital - follows nerve through supraorbital foramen (forehead)

Anterior ethmoidal - follow nerve to paranasal sinus

Posterior ethmoidal - follow nerve to paranasal sinus

Supratrochlear - follows nerve to superiomedial forehead

36
Q

What are the 3 layers of the eye?

A

Sclera (outermost coat) - helps the eye hold its shape

Choroid (middle) - “Uveal layer” - where arteries and nerves travel (i.e. ciliary branches)

Retina (inner)

37
Q

How many layers does the cornea have?

A

5

38
Q

Where is the ciliary muscle of the eye and what is it’s function?

A

The ciliary muscle is in the uveal layer of the eye and travels around the lens.

Contraction: releases tension on zonular fibers (suspensory ligaments) that will fatten the lens.

Relaxation: forces tension on zonular fibers (suspensory ligaments) that will flatten the lens (normal baseline)

39
Q

What innervates the ciliary muscle?

A

CN 3

40
Q

What makes aqueous humor? Where does it drain?

A

The ciliary process; the canal of Schlemm

41
Q

True or false: In both rods and cones, THERE ARE NO ACTION POTENTIALS

A

True

42
Q

Specialized for night vision

A

rods

43
Q

Specialized for daylight

A

cones

44
Q

Captures more light

A

rods

45
Q

Captures less light

A

cones

46
Q

Saturate in daylight

A

rods

47
Q

Low acuity, absent in the fovea

A

rods

48
Q

High acuity, especially in the fovea

A

cones

49
Q

Light travels from ________ , through __________, to ________.

A

From ganglion cells, through interneurons, to photoreceptors.

50
Q

True or false: Rods exist in the fovea

A

FALSE
In the fovea, receptors are almost exclusively cones AND there is almost a 1:1 ratio of ganglion cells to the photoreceptors

51
Q

What forms the blind spot in the eye?

A

The optic disc of the optic nerve because it does not contain photoreceptors.

52
Q

What are the layers of the optic nerve (inner to outer)?

A 
Optic nerve
Pia Mater
Subarachnoid Space
Arachnoid Sheath
Dura Sheath
53
Q

What artery supplies the retina?

A

The central artery from the ophthalmic nerve

54
Q

If there is pressure in the eye, what gets compressed first?

A

The central vein, resulting in papilledema.

55
Q

How does the optic nerve leave the eye?

A

The optic nerve leaves the eye via axons through the lamina cribrosa of the sclera.

SHB Exam 2 (15 decks)

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