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MBBS II HNNS > L42 - Orbit > Flashcards

L42 - Orbit Flashcards

1
Q

Define the bones that form the medial wall of the orbit?

A

Medial wall:

a. Frontal process of Maxilla
b. Lacrimal bone
c. Orbital plate of ethmoid
d. Body of sphenoid

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2
Q

Bones that form the Inferior wall of orbit?

A

a. Medial part: Maxillary bone
b. Lateral part: Zygomatic bone
c. Posterior part: Palatine bone

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3
Q

Bones that form the Lateral wall of orbit?

A

a. Anterior part: zygomatic bone

b. Posterior part: Greater wing of sphenoid

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4
Q

Bones that form the Superior wall of orbit?

A

a. Anterior part: Frontal bone

b. Posterior part: Lesser wing of sphenoid

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5
Q

Define the divisions of the orbital fissure?

A
  • Divided into the superior and inferior orbital fissure

- Separated into 3 segments by the annulus of Zinn

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6
Q

Which part of the orbit is most prone to blowout fracture?

A

posteromedial aspect of orbital floor (thin)

where infraorbital nerve passes through infraorbital foramen

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7
Q

Which bone forms the orbital fissure?

A

Sphenoid bone

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8
Q

Superior orbital fissure: Extraconal (outside annulus of Zinn) content?

A

 Lacrimal nerve (V1)
 Frontal nerve (V1): Supraorbital nerve Supratrochlear nerve

 Trochlear nerve (CN IV): superior oblique muscle
 Superior ophthalmic vein

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9
Q

Intraconal (inside annulus of Zinn) superior orbital fissure content?

A

Nasociliary nerve (V1): branches:

  • Infratrochlear nerve
  • Long ciliary nerves
  • Short ciliary nerves

Abducens nerve (CN VI): lateral rectus muscle

Oculomotor nerve (CN III):  Superior division 
 Inferior division
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10
Q

Describe the origins of the Long and Short ciliary nerves?

A

 Long ciliary nerves (postsynaptic/postganglionic sympathetic fibers from superior cervical ganglion)

 Short ciliary nerves (postsynaptic parasympathetic fibers from oculomotor nerve, synapse at ciliary ganglion)

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11
Q

The optic nerve passes through the superior orbital fissure inside the annulus of Zinn. T or F?

A

False

Inside annulus of Zinn but passes outside the sup. orbital fissure through optic canal

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12
Q

Content of the Inferior orbital fissure?

A

Inferior ophthalmic vein

Maxillary nerve (V2) and branches:

  • Zygomaticotemporal nerve
  • Zygomaticofacial nerve
  • Infraorbital nerve
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13
Q

Which nerve passing through the orbital fissures cause numbness that radiate to teeth when damaged?

A

Infraorbital nerve (through inferior orbital fissure)

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14
Q

Define the sensory nerve supply of the orbit?

A

Optic nerve: for vision

V1: superior orbital sensation, Upper eyelids

  • Nasociliary n.
  • Ant + post. Ethmoid,
  • Frontal n.,
  • Supraorbital n.
  • Lacrimal n.

V2: inferior orbital sensation, lower eyelids

  • Infraorbital nerve,
  • zygomatic n.
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15
Q

Motor supply of the orbit?

A
  • CN III, IV, VI for Extraocular muscles
  • CN III: opening of eyelids (levator palpebrae superioris)
  • CN VII: for eye closure and brow movement.
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16
Q

Define the blood supply to the anterior segment of the eyeball?

A
  • Iris + ciliary body:
    Long Post ciliary artery (runs through the choroid) anastomose with Ant. Ciliary Artery (runs to anterior segment through extraocular muscles).
  • Forms major and minor arterial circles on the iris
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17
Q

Define what is supplied by the Long posterior ciliary artery?

A

Recurrent branches supply the choroid anterior to equator

Anastomose with Anterior ciliary artery and Short Posterior Ciliary artery

18
Q

Define what is supplied by short posterior ciliary artery?

A

Supply choroid posterior to equator + Optic disc

19
Q

Define what is supplied by Anterior ciliary artery?

A

7 arteries, 2 for each rectus muscle except Lateral Rectus (only 1)

Supply sclera, conjunctiva, iris

20
Q

Define the posterior arterial supply of the eyeball?

A

Retina: Central Retinal artery (runs along optic nerve)

Fovea avascular zone = no capillaries over fovea

Choroid:
- Short posterior ciliary artery (anastomose with long posterior ciliary a.)

21
Q

What forms the blood retinal barrier?

A

Tight junctions of the Retinal Pigmented epithelium

Separate choroidal and blood circulation = immune privileged site

22
Q

Venous drainage of eyeball?

A

Retina: Central retinal vein

Choroid: 4 vortex veins (2 on each side) Exit eyeball posterior to equator

  • Superior Vortex + central retinal vein&raquo_space; superior Ophthalmic vein&raquo_space; supraorbital vein + facial v.
  • Inferior vortex vein&raquo_space; inf. Ophthalmic v.&raquo_space; Ophthalmic v/pterygoid venous plexus/Cavernous sinus
23
Q

Define Hyphema

A

bleeding that fills the anterior segment of the eye

24
Q

Explain why Central retinal artery occlusion results in a Cherry red spot?

A

When the retinal circulation is occluded by a emboli, the choroidal circulation is unaffected

whole retina is pale because of a lack of retinal circulation. But the thinnest part at the fovea shows through as a “cherry red spot” of the underlying choroidal ciruclation

25
Q

List the cavities located around the orbit?

A 
Superior = Anterior cranial fossa 
Medial = Nasal cavity and ethmoid air cells 
Inferior = Maxillary sinus 
Postero-Lateral = Middle cranial fossa
26
Q

Define the sinuses that lie medial to the orbit?

A

Anterior, middle and posterior ethmoid sinus

Middle meatus

27
Q

List the nerves and arteries that pierce the medial orbit wall

A

Ant. and post. ethmoid nerve
Infratrochlear n.
Terminal branch of opthalmic artery

28
Q

List the sinuses that lie inferior to the orbit?

A

Maxillary and palatine sinus

29
Q

List the vessels and nerves that are found on the lateral wall of the orbit?

A

Lacrimal nerve and vessels

Zygomatic nerves and branches

30
Q

List the structures found at the superior wall of the orbit?

A 
Periorbital fat 
Frontal nerve 
Trochlear nerve 
Levator Palpebrae superioris 
Superior rectus 
Superior oblique 
Lacrimal gland
31
Q

List the veins that drain the orbit?

A

Superior = Supratrochlear and Supra-orbital veins

Medial = Opthalmic and angular v.

Lateral = Superficial temporal v.

32
Q

Compare the action of the Superior and inferior oblique muscles?

A

obliques act opposite to their names + abduct

Superior oblique: Intorsion, Depression , Abduction

Inferior oblique:
Extorsion, Elevation , Abduction

33
Q

List the actions of all the rectus musces?

A

MR - Adduction

SR - Elevation, Adduction, Intorsion

LR - abduction

IR - Depression, Adduction, Extortion

34
Q

Role of suspensory ligaments of eyeball?

A

suspends the eyeball of the orbital space

Act as fulcrum/ pulleys for extraocular muscles

35
Q

Function of eyelids?

A
  • eyelashes to protect from dust, foreign body, and perspiration
  • To regularly spread tears and other secretions to keep the eye moist
  • Blink and menace reflex protect the eye from foreign body
36
Q

Compare asian with caucasion eyelids?

A

Asian:
Lower lid crease

Smaller tarsal plate (cartilage)

Lower orbital fat

50% people have single lid crease

37
Q

Blood supply of eyelids?

A

Marginal and Peripheral/ Superior and inferior palpebral arterial arcades

= anastomosis between the facial artery and branches + medial and lateral palpebral arteries

38
Q

Define the nerves that provide sensation to parts of the eyelids?

A

Superior eyelid = Supraorbtal and Supratrochlear

Inferior eyelid = Infraorbital nerve

39
Q

Venous drainage of eyelids?

A

Superior and inferior palpebral veins

Branches of the facial vein: angular, anterior facial (medial)

Superficial temporal vein (lateral)

Supraorbital and Supratrochlear veins (superior)

40
Q

Drainage of tears?

A 
Superior and inferior puntum 
> Upper and Lower Lacrimal canaliculus 
> Common canaliculus  
> Lacrimal sac 
> Nasolacrimal duct 
> Opening of nasolacrimal duct into Inferior nasal meatus
41
Q

What maintains tears from quickly evapourating?

A

Meibomian glands at the lid margin makes meibom to prevent tears from quickly evaporating

42
Q

Pathogenesis of Dacrocystitis?

A

Dacrocystitis occurs when the Nasolacrimal duct is blocked. Bacteria infect

MBBS II HNNS (57 decks)

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