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Orbit And Osteology Flashcards

1
Q

What are the two main parts of the skull

A

The skull is divided into two parts the neurocranium/cranium - these are - basically from the lower forehead and all of the bones which contain the brain - these include the frontal, partial, occipital , temporal (which correspond to the lobes of the brain) and the sphenoid and ethmoid which are at the front - these are joined together by sutures - when your a baby they aren’t fused

The facial Skelton/viscerocranium

Composed of a large number of bones united by sutures

Has a number of cavities - called sinuses

Many cranial bones contain sinuses

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2
Q

What is the function of the orbits

A

The orbits are 2 pyramidal shaped boned cavities which support and protect the eye - they provide attachment points for the extra ocular muscles - and protect the eye from damage

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3
Q

What do the orbits contain

A
  • the eyeball
  • the extra ocular muscles
  • nerves
  • vessels
  • fat
  • lacrimal apparatus
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4
Q

Which bones comprise the orbit

A
  • seven bones form the boundaries of the orbit
Sphenoid - greater and lesser wing (between these is the superior orbital fisssure)
Ethmoid 
Lacrimal
Frontal 
Maxilla 
Paletine 
Zygomatic
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5
Q

Where do each of the bones that comprise the orbit lie anatomically

A
  • the frontal bone (which is part of the neurocranium) is at the top at forms a large part of the orbital roof
  • the sphenoid bone sits underneath that - has a greater wing a lesser wing and a body - that comprises a lot of the formations which things enter the orbit through e.g. optic canal, superior orbital fissure, inferior orbital fissure
  • in the medial aspect you have the ethmoid bone , the lacrimal bone , Body of the sphenoid , maxilla
  • inferorly - paletine , maxilla, zygomatic bone
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6
Q

What structure passes through the lesser wing of the sphenoid bone

A
  • the optic canal
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7
Q

What foramina is situated between the greater and lesser wing of the sphenoid bone

A
  • superior orbital fissure
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8
Q

What bones form the superior wall of the orbit

A
  • roof (superior wall) - made from the frontal bone and the lesser wing of the sphenoid
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9
Q

What bones form the medial wall of the orbit

A

Medial wall - ethmoid , maxilla, lacrimal and sphenoid body

The ethmoid bone separates the orbit from the ethmoid sinus

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10
Q

What bones comprise the inferior wall of the orbit

A
  • the maxilla , paletine and zygomatic bones , the maxilla separates the orbit from the maxillary sinus
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11
Q

What bones comprise the lateral wall of the orbit

A
  • lateral wall is formed by the zygomatic bone and the greater wing of the sphenoid
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12
Q

What are the 3 posterior foramina

A
  • superior orbital fissure (between the lesser and greater wing of the sphenoid bone)
    Inferior orbital fissure
    Optic canal
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13
Q

What are the 4 anterior foramina

A
  • these allow nerves to escape anteriolly out of the orbit
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14
Q

What are the nerves and blood vessels that supply the orbit and enter through the optic canal called?

A
  • optic nerve and opthalmic artery
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15
Q

Where is the superior orbital fissure located and how is it divided

A
  • located between the greater and lesser wing of the sphenoid bone
  • divided into three by the annulus of zinn (common tendinous ring)
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16
Q

Where do all of the recti muscles originate from

A
  • the common tendinous ring
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17
Q

What does the superior orbital fissure contain

A
  • you have a part superior to the common tendinous ring , a part within the common tendinous ring and a part inferior to it

Trochee are nerve

  • superior to the CTR - = the superior ophthalmic vein - (goes through the superior orbital fissure superior to the common tendinous ring
  • the lacrimal and frontal nerves - these are branches of the opthalmic branch - which is a branch of the trigeminal branch
  • the oculomotor nerve ( cranial nerve 3) - (which is within the ctr - you have two divisions - the superior and inferior division of the oculomotor nerve

Abducens nerve - cranial nerve 6

  • nasocillary nerve - another branch of the opthalmic branch which is a branch of the trigemnial nerve

(Branch of inferior opthalmic vein)

-

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18
Q

What are the four nerves within the common tendinous ring in the superior orbital fissure

A
  • superior division of the oculomotor nerve
  • nasocillary nerve - which is a branch of v1 which itself is a branch of the trigeminal nerve
  • inferior division of the oculomotor nerve
  • abducens nerve
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19
Q

Which nerves do the common tenditonous ring contain?- i.e. what nerves come into the orbit through the common tendinous ring (This is different to the contents of the superior orbital fissure)

A

From superior to inferior

One canal several orbital nerves in one annulus

  • optic canal- this contains the (optic nerve and the opthalmic artery)
  • superior division of the oculomotor nerve

Nasocillary nerve

Inferior division of the oculomotor nerve

Abducens nerve

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20
Q

What does the inferior orbital fissure contain

A
  • infraorbital nerve (branch of the maxillary division of cranial nerve 5)
  • zygomatic nerve ( branch of the maxillary division of cranial nerve 5 )
  • branches of pterygopaletine ganglion (sympathetic branches)
  • inferior opthalmic vein
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21
Q

What are the four anterior foramina of the orbit called

A
  • these lie on the anterior boundary of the orbit

supraorbital

  • infra orbital
  • zygomaticofacial
  • zygomaticotemporal (lies above zygomaticofacial for amen)
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22
Q

What nerves go through the supraorbital foramina

A

Supraorbital nerve goes through the supraorbital foramina

23
Q

What nerve goes through the infraorbital foramina

A

Infraorbital nerve

24
Q

What nerves go through the zygomaticofacial and sygimaticotemporal foramina

A

Zygomaticotempotal- zygomaticotemporal nerves

Zygomaticofacial - zygomaticofacial nerves

25
Q

How many posterior formanina and anterior formanina are their

A

Three posterior - superior orbital fissure , inferior orbital fissure , optic canal

4 anterior foramina = zygomaticotemporal , zygomaticofacial, infraorbital , supraorbital

26
Q

Within the common tendinious ring whch four nerves travel through the superior orbital fissure

A
  • superior and inferior division of the oculomotor nerve
  • abducens nerve
  • nasocillary branch of the opthalmic division of the trigeminal nerve
27
Q

What are the four parental sinuses

A
  • frontal
  • ethmoid
  • maxillary
  • sphenoid
28
Q

What are the functions of the paranasal sinuses

A
  • air filled spaces surrounding nasal cavity

No consensus of function but likely a combination of

  • decrease mass whilst maintaing structure
  • increased voice resonance
  • isolation of sensitive structures (roots of teeth, eyeballs , temperature fluctuations during inhalation and exhalation
  • humidifcation and warming of inhaled air
29
Q

Why are paradisal sinuses important for the eyes

A
  • due to their proximity to the orbit
  • the ethmoid sinus- part of the ethmoid bone is medial to the orbit
  • maxillary sinus is inferior to the orbit
  • the bone separating the maxillary sinus from the orbit is very thin
30
Q

What is the clinical significance of the orbital walls being thin

A
  • leaves them vulnerable to fracture “orbital blowout fractures’
  • if the inferior wall is fractured - you can have prolapse of the orbital contents into the maxilllary sinus
31
Q

During blowout fractures of the orbital floor what nerve is damaged

A
  • the infraorbital nerve - supplies sensation to the cheek - therefore patients often present with numbness of the cheek on the side of the trauma ,bruising around the eyes and the eyes sink a bit lower in the globe because you have loss of the fat from the orbit into the sinus-when it prolapses down the eye sinks down in the socket and if you have entrapment of some of the eom you have limitation of upward gaze because you have trapped them within the eom
32
Q

What is the clinical relevance of orbital blow out fractures

A
  • medial and inferior walls are thin and vulnerable to fracture in response to blunt force trauma - orbital contents can hermitate into the ethmoid and maxillary sinuses
33
Q

What other conditions do the thin orbital walls predispose patients to ?

A
  • as well as blowout fractures the thin walls also predispose patients to transmission of infection (orbital cellulitis)
  • if you have a infection in your sinus it can quite easily track across and go into your orbit - which = orbital cellulitis - cellulitis is an inflammation of soft tissues

Orbital celllulitis is therefore inflammation of the soft tissues of the orbit

34
Q

What factors facilitate direct extension of sinusitis into the orbit

A

Multiple factors facilitate direct extension of sinusitis into the orbits

  • the orbit is surrounded by the paranasal sinuses
  • the bony walls that separate the paranasal sinuses from the orbit are thin providing a permeable barrier
  • extension of infection from the sinus is the most common route by which orbital cellulitis develops
  • the veins that drain the sinuses (orbital veins) are valveless which allow both anterograde and retrograde spread of infections
35
Q

What is the most common cause of orbital cellulitis

A

(Transmission from the paranasal sinuses into the orbit)

36
Q

What happens in a orbital blowout fracture

A

Orbital contents may herniate into paranasal sinuses

37
Q

What symptoms will a patient with a orbital blowout fracture present with

A
  • numbness of cheek
  • lowering of globe
    Restriction of eye movements
38
Q

What does the orbit contain

A

Periorbita

Fat

Muscles - extrocular muscles

Tenons capsule

Globe - eyeball

Lacrimal gland

Lacrimal gland

39
Q

What is the periorbita

A
  • the periorbita is the orbital periosteum - most superfical layer of the orbit
  • all the bones in the body have a layer surrounding them called periosteum (which is a thin layer surrounding the bones) in the orbit it is called the periorbita
  • layer loosely attached to the bone
40
Q

What is tenons capsule

A
  • thin collagen rich membrane which surrounds the globe and the muscles and the optic nerve
  • surrounds everything in the eye
  • where it surrounds the eye it leaves a potential space between tenons capsule and the globe (episcleral space) - useful for injecting things into - i.e. numbing the eye
  • sub tenons injection
  • anterilly it merges with the conjuctiva at the limbus

-

41
Q

The lacrimal bone is a constituent of which orbital wall

A
  • medial wall
42
Q

What bone is situated right next to the lacrimal bone

A
  • the ethmoid bone
43
Q

What bone covers most of the superior aspect of the orbit

A
  • the frontal bone
44
Q

What bone forms the medial and inferior parts of the orbit

A
  • the maxilla
45
Q

Where does the superior orbital fissure lie

A

Between the greater and lesser wing of the sphenoid bone

Superior orbital fissure divides the wings of the sphenoid bone

46
Q

Which nerves travel through the superior orbital fissure within the common tendinous ring

A
  • inferior division of the oculomotor nerve
  • superior division of the oculomotor nerve
  • nasocillary
  • abducens
47
Q

What nerves travel superior to the ctr in the superior orbital fissure

A
  • frontal
  • trochlea
  • lacrimal
48
Q

What nerves travel through the superior orbital fissure

L f t s n i a

A

Lacrimal

Frontal

Trochlear nerve

Superior division of oculomotor nerve

Nasocillary

Inferior division of oculomotor nerve

Abducens nerve

49
Q

Which formanina does the zygomaticotemporal nerve exit the orbit via

A
  • zygomaticotemporal foramena
50
Q

What are the sensory nerves of the orbit

A

The frontal nerve divides and then you get the supraorbital nerve travelling through the supraorbital foramen and then the superior tracheal nerve - the nasocillary nerve passes within the annulus of zinn that gives off the posterior ethmoid and the anterior ethmoid nerves which travel through the posterior and anterior foramens and the infratrochlear nevre

Zygomatico nerve , zygomaticofacial nerve , infraorbital nerve

They supply sensation to the nerves of the tissues of the orbit and the surrounding cheek and facial areas

51
Q

What is Hutchinsons sign

Herpes zoster opthalmicus

A
  • Hutchinsons sign is where you have the rash extending with vesicles on the tip of the nose
  • significant because the nasocillary nerve which passes within the ctr supplies innervation to the cornea and the sclera aswell as the tip of the nose
  • so if you have a vesicle on the tip of the nerve it means that the virus is reacted within the nasocillary nerve - means that the eye itself is at risk
  • HZO is shingles of the opthalmic branch of the trigeminal nerve
  • nasocillary nerve innervated both tip of the nose and the cornea
  • vesicle on nose tip (Hutchinsons sign) therefore of significance in predicting corneal involvement
52
Q

A person as brushing and restricitng pg upward gaze in the right eye following assault - he has numbness overlying his cheek herniation of orbital contents into which sinus and damaged to which vulnerable sensory nerve is likely to explain his presentation

A
  • maxillary sinus , infraorbital nerve

(Hypoglobus is inferior dispalcement of the globe)

Because you have inferior displacement of the eye and restriction of upward gaze - when you have orbital contents (inferior rectus is trapped in the maxillary sinus) the superior rectus is unable to move the eye upwards

Infraorbital nerve supplies innervation to the cheek and is vulnerable to damage- infraorbital nerve travels along the orbital floor and comes out through the infraorbital foramen -

53
Q

Which nerves travel through the superior orbital fissure within the common tendinous ring

A
  • superior division of oculomotor nerve
  • nasocillary nerve
  • inferior division of the oculomotor nerve
  • abducens
54
Q

What is a common presentation of patients with orbital blowout fractures

A
  • hypoglobus
  • anaesthesia of cheek from damage to the infraorbital nerve
  • bruising around the eye
  • limitation of upward gaze - caused by entrapment of the tissues within the fracture

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