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Anatomy - Head and Neck > 5 - Orbit > Flashcards

5 - Orbit Flashcards

1
Q

What is the orbit?

A

A pyramidal-shaped bony cavity.

The medial walls are parallel and the lateral walls are perpendicular.

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2
Q

What are the four orbital margins? What is each made up of?

A
  1. Supraorbital: frontal bone and supraorbital notch
  2. Lateral: frontal bone and zygomatic bone
  3. Infraorbital: zygomatic bone and maxilla
  4. Medial: maxilla and frontal bone
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3
Q

What are the four skin layers of the eyelids from superficial to deep?

A
  1. Skin
  2. Muscle
  3. Tarsal plates and orbital septum
  4. Conjunctiva
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4
Q

What is the opening of the eye (between the eyelids) called? What are the corners of the opening called?

A

The palpebral fissure.

Medial and lateral angles or canthi.

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5
Q

What is the skin of the eye continuous with as you go around the margins?

A

The conjunctiva.

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6
Q

What are the tarsal plates connected to (ie what muscles and ligaments)? What else is nearby?

A

The superior tarsal muscle (smooth muscle-involuntary) and the levator palpebrae superioris that helps lift the eyelid.

Linked to bone by medial and lateral palpebral ligaments.

Also tarsal glands nearby that secrete oily fluid that forms a later over the tear and prevents it from evaporating.

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7
Q

What are the different parts of your palpebral of the conjunctiva (lining of your eyelid)?

A

It covers the deep surface of your eyelids, at the top of the margin it folds over and starts to cover the the cornea where it’s called the bulbar conjunctiva.

The reflection is called the superior fornix.

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8
Q

What is located at the superior fornix?

A

The openings of the lacrimal gland.

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9
Q

What are the characteristics of the lens of the eye? What controls its size?

A

Transparent, avascular structure held in place by the zonule fibers that pull on it to control the thickness.

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10
Q

What is in the anterior cavity of the eye?

What is in the posterior cavity?

A

Anterior cavity: Aqueous humor, anterior chamber, posterior chamber (between the iris and cornea.

Posterior cavity: vitreous humor (between the lens and the iris)

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11
Q

What are the three layers of the eyeball? What’s in each?

A

Fibrous tunic: sclera and cornea

Vascular tunic: Choroid, ciliary body, iris

Neural layer: retina

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12
Q

What is the sclera of the eyeball?

A

The whites of your eyes, made of a dense fibrous connective tissue that’s posteriorly pierced by the optic nerve.

Anteriorly continuous with the cornea.

Extraocular muscles insert here.

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13
Q

What is the cornea of the eyeball?

A

Major refractive structure that’s avascular and transparent.

Makes up the anterior 1/6th of the fibrous tunic.

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14
Q

What is the function of the choroid of the eyeball?

A

Part of the vascular tunic that lines the posterior 5/6 of the eyeball.

Provides nutrition to the cells of the retina.

Anteriorly this becomes the ciliary body.

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15
Q

What is the function of the ciliary bodies? What is the path of aqueous humor?

A

Contains ciliary muscle that controls the zonule fibers that connect to the lens.

Has epithelium that secretes aqueous humor, which enters the posterior chamber and flows through the pupil and into the anterior chamber. Then its reabsorbed into a venous meshwork and returns into the venous system.

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16
Q

What happens to the lens when the ciliary muscles contract?

A

The zonula fibers become slack and reduce their pull on the lens, which allows the lens to thicken for near vision.

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17
Q

Where is the lacrimal gland and where does it drain to?

A

Superolateral, drains into the superior fornix to collect in the lacrimal lake and enter openings called the lacrimal puncta.

From there they are sucked into lacrimal canaliculli and lacrimal sack to drain inferiorly through the lacrimal duct into the inferior nasal meatus.

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18
Q

What are the branches of the ophthalmic artery?

A
  1. Central artery of the retina
  2. Lacrimal a.
  3. Supraorbital a.
  4. Supratrochlear a.
  5. Dorsal nasal a.
  6. Posterior and anterior ethmoidal a.
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19
Q

What are the veins in the orbital region?

A

Central v. of the retina, superior ophthalmic v., inferior ophthalmic v.

Have connections to the cavernous sinus and facial veins.

20
Q

What is the route of the optic nerve (CN II)?

A

Axons of retinal ganglions pierce the sclera medial to the posterior pole of the eyeball and exit through the optic canal of sphenoid bone.

Optic tracts terminal in the lateral geniculate nucleus.

21
Q

What is the route of the opthalmic (somatic sensory) branch of the trigeminal nerve?

A

Sensation from sensory receptors through SOF and cav sinus to neuron cell bodies in the trigeminal ganglion.

Enters brainstem at mid level of pons and transmits info to principal sensory nucleus and spinal nucleus of V.

22
Q

What are the more superficial (near top of orbit) branches of the Ophthalmic nerve (V1)?

A

Lacrimal n (lateral) and the frontal nerve (middle of orbit).

Frontal n. branches: supratrochlear, supraorbital, N. to frontal sinus.

23
Q

What are the deeper branches of the Ophthalmic nerve (V1)?

A

The Nasociliary n. with branches:

Ant. and post. ethmoidal, infratrochlear, meningeal, long and short ciliary nerves.

24
Q

What structures of the orbit have autonomic innervation?

A

Lacrimal gland, sphincter pupillae m., ciliary m., dilator pupillae m., superior tarsal m.

25
Q

What is the pathway of parasympathetic innervation of the lacrimal gland?

A

Cell bodies in the superior salivatory nucl. and travel with the nervous intermedius, through the geniculate ganglion.

Then the greater petrosal n. and the deep petrosal nerve form the nerve of the pterygoid canal. They synapse at the pterygopalatine ganglion.

Zygomaticotemporal n. and lacrimal n. innervate the lacrimal gland.

26
Q

What is the pathway of sympathetic innervation of the lacrimal gland?

A

Begins at lateral horn of spinal cord, travel through the ventral root, spinal nerve, ventral primary ramus, and white commun. rami to the superior cervical ganglion.

The internal carotid n, deep petrosal n. and greater petrosal nerve meet to become the N. of the pterygoid canal, zygomaticotemporal n. and the lacrimal nerve.

These cause vasoconstriction of the glandular cells.

STOP LACRIMATION.

27
Q

What is the parasympathetic innervation of the sphincter pupillae m. (smooth muscle of the orbit)? What does it result in?

A

Edinger-westphal nucleus in midbrain then out via CN III to the ciliary ganglion.

Short ciliary n (V1) go to innervate the sphincter pupillae m. and ciliary m.’s causing slacking of the zonule fibers.

Lens thickens and you can focus on near objects.

28
Q

What is the sympathetic innervation of the sphincter pupillae m. (smooth muscle of the orbit)? What does it result in?

A

Spinal cord to superior cervical ganglion and then via the internal carotid plexus, ciliary ganglion, and long ciliary n. (V1) to innervate the dilator pupillae and superior tarsal m.

Causes dilation of pupils and opening of eyelids wider.

29
Q

What happens when there’s an injury to the sympathetic pathway of the sphincter pupillae muscle?

A

Eyelids will droop (ptosis) and the pupil won’t dilate (myosis).

30
Q

What is extorsion of the eyeball? What is intorsion?

A

Extorsion - twists laterally/temporally.

Intorsion - twists medially and nasally.

31
Q

What cranial nerve innervates the muscle that raises the upper eyelid?

A

CN III - oculomotor

Innervates the levator palpebrai superioris

32
Q

What innervates the lateral rectus muscle?

What about the medial rectus muscle?

A

Medial rectus: CN III - occulomotor

Lateral rectus: CN VI - abducens

33
Q

What is the function of the superior rectus muscle? What CN innervates it?

A

CN III - occuolomotor nerve

Elevates, adducts, and intorts the eye

34
Q

What is the function of the inferior rectus muscle? What CN innervates it?

A

CN III - occulomotor nerve

Depresses, adducts, and extorts the eye.

35
Q

What is the function of the superior oblique muscle? What innervates it?

A

CN IV - trochlear nerve.

Depresses, abducts, and intorts the eye

36
Q

What is the function of the inferior oblique muscle? What innervates it?

A

CN III - occulomotor nerve

Elevates, abducts, and extorts the eye

37
Q

What is an important thing to remember when testing a patient’s extraoccular eye muscles?

A

You need to have them allign their axis of gaze with the long axis of the muscle you’re testing.

38
Q

How would you test a patients lateral rectu and medial rectus muscles?

A

Looking right tests their right lateral rectus and left medial rectus.

Looking left tests the left lateral rectus and right medial rectus.

39
Q

Superior rectus and inferior oblique both elevate the eye, how do you test each individually?

A

Superior rectus: have them look laterally to align with axis, and then look up.

Inferior oblique: align with axis by looking medially, and then have them look up.

Keep in mind that when they do this each eye is testing a different muscle.

40
Q

The inferior rectus muscle and the superior oblique muscle both depress the eye. How do you tell if each individual muscle is working?

A

Inferior rectus: tell them to look laterally and then ask them to look down

Superior oblique: tell them to look medially and then down

Keep in mind that these commands result in testing a different muscle in each eye.

41
Q

How do you remember how to test the superior oblique and inferior oblique?

A

O’s to the nose and upside down.

Have them look medially, then:
Superior oblique: look down
Inferior oblique: look up

42
Q

A patient comes in and cannot open one of their eyes. What CN is damaged?

A

CN III - occulomotor.

This is called ptosis, and occurs because the levator palpebrae is wiped out.

The eyeball will also be deviated laterally, down, with dilated pupil because of the unopposed action of the lateral rectus, superior oblique, and sphincter pupillae

43
Q

A patient comes in and has one eye that is deviated medially. What CN is damaged?

A

CN VI - abducent nerve.

The lateral rectus muscle is unable to work, therefore the medial rectus is unopposed causing the eye to move medially.

44
Q

A patient comes in complaining of diplopia (double vision) that becomes worse when he tilts his head to the left but resolves when he tilts his head to the right. What is your diagnosis?

A

CN IV palsy- trochlear nerve innervates the superior oblique. Unopposed inferior oblique causes extortion of the L eye.

He therefore cannot intort his left eye (towards the nose).

When you tilt your head to the right, the R eye will extort and the L eye will intort. Since he can’t intort his left eye, his diplopia will worsen.

45
Q

What occur with injury to sympathetic fibers? What are the symptoms?

A

Horners syndrome:

  • Ptosis: drooping eyelids
  • Miosis: pupil contriction
  • Anhidrosis: lack of sweating
46
Q

What are symptoms of injury to parasympathetic fibers with CN III (oculomotor)?

A

Normally parasympathetic fibers will constrict the pupils for accomodation.

When injured, they cannot do this and will therefore be dilated and lose the ability to accommodate to light.

Anatomy - Head and Neck (13 decks)

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