The Orbit and Associated Structures Flashcards Preview

ESA 4 - Head and Neck > The Orbit and Associated Structures > Flashcards

Flashcards in The Orbit and Associated Structures Deck (23)
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1
Q

What are the orbital and optical axis?

A

The orbital axis is the axis in which the eyes and optic nerve follow coming from the brain, it forms a triangle shape coming outwards from inside the head

The optical axis are the direction in which the eyes actually face, they are parallel and face forward

2
Q

What are the bones of the orbit?

A

Roof - frontal and sphenoid

Floor - maxilla, zygomatic (and palatine)

Medial - ethmoid, maxilla and lacrimal bones

Lateral - zygomatic and sphenoid

3
Q

What are the orbital fissures and fossae? And their associated contents?

A

Optic canal - optic nerve

Superior orbital fissure - lateral to medial:

  • Lacrimal nerve
  • Trochlear nerve
  • Frontal nerve
  • Oculomotor nerve
  • Abducent nerve
  • Superior ophthalmic vein

Inferior orbital fissure - infraorbital nerve

Etc… more fissures and nerves

4
Q

Describe the optic nerve.

A

CN II
1.2m axons from retinal cells
Coverings of pia (delicate), arachnoid (web-like) and dura (tough) maters (mother) of meninges, continuous with the brain (infection spread route)
Central artery and vein
If there is raised ICP, then it can lead to venous engorgement, and then can lead to papilloedema

5
Q

What is the optic chiasma?

A

A place where some nerves cross over and some stay on the same side

6
Q

Where do fractures of the orbit usually occur?

A

Normally a blow-out fracture

Medial and inferior walls are the thinnest and so the ones normally fractured

The medial wall can involve the ethmoidal and sphenoidal sinus
The inferior wall can involve maxillary sinus

The dangers are infections from the sinuses and infraorbital bleeding

7
Q

What are the muscles of eye movement?

A

4 recti (straight) muscles:

  • Superior rectus muscle (pulls eye up)
  • Inferior rectus muscle (pulls eye down)
  • Lateral rectus muscle (pulls eye laterally)
  • Medial rectus muscle (pulls eye medially)

2 obliques (slanted) muscles:

  • Superior oblique muscle (intorsion) (down and in)
  • Inferior oblique muscle (extorsion) (up and out)

Controlled by three cranial nerves

8
Q

What are the nerves of the muscles of the eye movements?

A

Lateral rectus muscle - CN VI Abducent
Superior oblique muscle - CN IV Trochlear
The rest are CN III Oculomotor

9
Q

What is the main arterial supply of the orbit?

And where does it come from?

A

Ophthalmic artery
Branch of the internal carotid, via optic canal
Any blockage leads to immediate blindness

10
Q

Which artery supplies the internal surfaces of the eye and where does it arrive from?

A

Central artery of retina

Arises from the ophthalmic artery

11
Q

What are the main branches of the ophthalmic artery?

A

Central retinal artery
Lacrimal artery - lacrimal glands, eyelids, conjunctiva
Posterior ciliary arteries - posterior external eye
Muscular branches to extraocular muscles
Other spate branches to ethmoidal and frontal sinuses, eyelids, forehead and scalp etc….

12
Q

Describe the venous drainage of the orbit?

A

Superior ophthalmic vein
- From inner angle to orbit to SOF

Inferior ophthalmic vein
- From plexus on floor and medial wall to then drain
either by SOF or IOF

13
Q

What is the danger triangle?

A

IT is an area of the face over the nose where the facial veins communicate to the cavernous sinus via ophthalmic veins
This means infection can spread easily from the face to the brain

14
Q

What is the function of the eyelids?

A

Protect from light and injury

Prevent corneal drying, through controlled spread of lacrimal fluid (tears)

15
Q

What are the two angles between the eyelids called? and what is the space between the eyelids called?

A

Lateral and medial canthus

Palpebral fissure

16
Q

What is it called when there is a drooping of one eyelid?

A

A ptosis

17
Q

What are the muscles of the eyelids?

A

Opening:

  • Levator palpebrae superioris muscle. (CN III)
  • Superior tarsal muscle

Closing:
- Orbicularis oculi (CN VII)

18
Q

Describe the anatomy of the eyelid, from anterior to posterior

A

Skin
Areolar tissue
Fibres of orbicularis oculi (circular muscles around eye)
Levator palpebrae superioris
Superior tarsus
- dense connective tissue strengthening “skeleton”
- (Inferior tarsus in lower lid)
Tarsal (meibomian) glands, secrete oil (to keep fluid in eye and keep it moist) (if they aren’t working then get dry eyes)
Ciliary glands (sebaceous) (inflamed - stye)
Palpebral conjunctiva.

19
Q

Describe the bilateral blinking reflex

A
It protects eye and keeps them moist
Triggers:
   - Corneal drying
   - Corneal irritation or contact (perceived as pain)
   - Expectation of contact

Corneal blink reflex is via the CN V1 - sensory and CN VII)

20
Q

What happens if you get paralysis of Orbicularis oculi?

A

Innervated by CN VII - facial nerve

Failure to close eyes, e.g. Bells Palsy

Loss of blink and corneal reflex

Dry eyes, need eye drops

Infection likely

21
Q

What happens if you get paralysis of levator palpebrae superioris?

A

Innervated by CN III - occulomotor nerve

Drooping of the upper eyelid - known as ptosis

Vision compromised

Residual opening of the eye due to superior tarsal muscle (smooth muscle)

22
Q

What happens if you get paralysis of superior tarsal muscle?

A

Sympathetic innervation

It is smooth muscle

Minor drooping of the upper eyelid - known as partial ptosis

Vision usually ok

Eye opening is ok due to levator palpebrae superioris

Can be caused by Horner’s syndrome (with pupil constriction, etc…)

23
Q

Describe lacrimation

A

Lacrimal fluid (tears) is created by lacrimal glands in superior lateral border of the eye

Eyes close lateral to medial, tears collect at lacrimal lake (medial canthus)

Tears production:: parasympathetic fibres of facial nerve, CN VII

Sensory supply via lacrimal branch of the ophthalmic division of CN V (also to eyelid and conjunctiva)