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Fundamentals Flashcards

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1
Q

What is the volume of the bony orbit?

A

Approximately 30cm

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2
Q

What is the average height and width of the orbital entrance?

A

35mm in height 45mm in width

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3
Q

Where is the maximum width of the orbit?

A

Approximately 1 cm behind the anterior orbital margin.

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4
Q

What is the average depth of the orbit?

A

From 40 to 45 mm from the orbital entrance to the apex

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5
Q

What are the seven bones that make up the bony orbit?

A
  1. Frontal bone
  2. Zygomatic bone
  3. Maxilla (or maxillary bone)
  4. Ethmoid (or ethmoidal bone)
  5. Sphenoid bone
  6. Lacrimal bone
  7. Palatine bone
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6
Q

What bones make up the orbital margins?

A

Superior margin: Frontal bone (medially: supraorbital notch)

Medial margin: Above by the frontal bone, below by the posterior lacrimal crest of the lacrimal bone and the anterior lacrimal crest of the maxillary bone

Inferior margin: Maxillary and zygomatic

Lateral margin: Zygomatic and frontal

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7
Q

What bones make up the orbital roof?

A

Orbital plate of the frontal bone

Lesser wing of the sphenoid

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8
Q

What bones make up the medial orbital wall?

A

Frontal process of the maxillary bone

Lacrimal bone

Orbital plate of the ethmoid

Lesser wing of the sphenoid

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9
Q

What bone makes up the largest portion of the medial wall?

A

Ethmoid

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10
Q

Describe the location of the lacrimal fossa

A

Formed by the frontal process of the maxilla and the lacrimal bone

Below is continuous with the bony nasolacrimal canal which extends into the inferior meatus (beneath inferior turbinate)

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11
Q

What is the lamina papyracea?

A

Paper thin medial wall of ethmoid bone

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12
Q

What bones make up the orbital floor?

A

Maxillary bone

Palatine bone

Orbital plate of zygomatic bone

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13
Q

Describe the path of the infraorbital groove

A

Traverses the floor of the orbit and descend anteriorly into a canal.

Exits as the infraorbital foramen, below the orbital margin of the maxillary bone.

It transmits the infraorbital artery and vein, and the infraorbital nerve, a branch of the maxillary nerve.

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14
Q

What is the only EOM that does not originate from the orbital apex?

A

Inferior oblique.

The inferior oblique arises from the orbital surface of the maxilla, lateral to the lacrimal groove. Unlike the other extraocular muscles (recti and superior oblique), the inferior oblique muscle does not originate from the common tendinous ring (annulus of Zinn).

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15
Q

What is the slope of the orbital floor?

A

Downwards from posterior to anterior, 20 degrees

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16
Q

What fractures of the orbit are more common before puberty?

A

Trapdoor type fractures because the bones of the floor of the orbit are immature

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17
Q

What is the strongest orbital wall?

A

Lateral

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18
Q

What bones make up the lateral orbital wall?

A
  1. Zygomatic bone
  2. Greater wing of the sphenoid
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19
Q

What is Whitnall tubercle?

A

“Lateral orbital tubercle”

A small elevation of the orbital margin of the zygomatic bone approximately 11mm below frontozygomatic suture.

Because they all contain the letter L, I remember these structures as the “4 L’s”:

Lateral rectus check ligament

Lockwood suspensory ligament

Lateral palpebral ligament

Levator aponeurosis

Whitnall’s ligament does NOT attach to Whitnall’s tubercle.

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20
Q

Describe the location and structures associated with the optic foramen.

A

Leads from the middle cranial fossa to the apex of the orbit.

The optic foramen is the opening to the optic canal.

The canal is bound medially by the body of the sphenoid and laterally by the lesser wing of the sphenoid.

Conducts the:

  1. Optic nerve
  2. Ophthalmic artery
  3. Sympathetic fibers from the carotid plexus
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21
Q

Describe the location and structures of the supraorbital foramen

A

Located at the medial third of the superior margin of the orbit.

Transmits blood vessels and supraorbital nerve (branch of the ophthalmic (V1) division cranial nerve V.

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22
Q

Describe the location and structures of the anterior and posterior ethmoidal foramen

A

Located at the frontoethmoidal suture and transmits the anterior ethmoidal vessels and nerve.

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23
Q

Describe the location and structures of the zygomatic foramen

A

Lies in the lateral aspect of the zygomatic bone and contains the zygomaticofacial and zygomaticotemporal branches of the zygomatic nerve and artery.

(The zygomatic nerve (temporomalar nerve; orbital nerve) is a branch of the maxillary nerve (CN V2, itself a branch of the trigeminal nerve) that enters the orbit and helps to supply the skin over the zygomatic and temporal bones.

The zygomatic nerve arises in the pterygopalatine fossa. It enters the orbit by the inferior orbital fissure, and divides at the back of that cavity into two branches, the zygomaticotemporal nerve and zygomaticofacial nerve, which exit the orbit using identically named foramen.

The zygomatic nerve carries sensory fibers from the skin. It also carries post-synaptic parasympathetic fibers (originating in the pterygopalatine ganglion) to the lacrimal nerve via a communication. These fibers will eventually provide innervation to the lacrimal gland. These parasympathetic preganglionic fibers come from the facial nerve (CN VII).)

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24
Q

Describe the location and structures of the infraorbital canal

A

Continues anteriorly from the infraorbital groove and exits below the inferior orbital margin.

Transmits the infraorbital nerve which is a branch of V2 (maxillary division of CN V).

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25
Describe the location and structures of the superior orbital fissure.
Located between the greater and lesser wings of the sphenoid and lies lateral to and partly above and below the optic foramen. Approximately 22mm long and spanned by common tendinous ring of the rectus muscles (annulus of Zinn). Above the ring: 1. Lacrimal nerve of CN V1 2. Frontal nerve of CN V1 3. CN IV (trochlear nerve) 4. superior ophthalmic vein Within the ring of between the two heads of the rectus muscles are: 1. Superior and inferior division of CNIII (oculomotor nerve) 2. Nasociliary branch of CNV1 3. Sympathetic roots of ciliary ganglion 4. CN VI (abducens nerve) Mnemonic: Lazy French Tarts Sit Nakedly In Anticipation The order of the nerves passing through the superior orbital fissure from superior to inferior: L: lacrimal nerve (branch of CN V1) F: frontal nerve (branch of CN V1) T: trochlear nerve (CN IV) S: superior division of the oculomotor nerve (CN III) N: nasociliary nerve (branch of CN V1) I: inferior division of the oculomotor nerve (CN III) A: abducens nerve (CN VI)
26
What structure within the superior orbital fissure is variable?
The inferior ophthalmic vein, can travel above or within the ring, typically above
27
Describe the structure and location of inferior orbital fissure
Lies just below the superior fissure between the lateral wall and the floor of the orbit. Provides access to the pterygopalatine and inferiotemporal fossae. Close to foramen rotundum and pterygoid canal. Transmits the infraorbital and zygomatic branches of CNV2, an orbital nerve from the pterygopalatine ganglion and the inferior ophthalmic vein. The vein connects with the pterygoid plexus before draining into the cavernous sinus.
28
Describe what borders the anterior and posterior medial walls of each orbit respectively
Anterior: nasal cavity Posterior: ethmoid and sphenoid sinuses
29
Describe what borders the lateral walls of the orbits
The lateral wall of each orbit borders the middle cranial, temporal and pterygopalatine fossae
30
Describe what borders the superior wall of the orbit
anterior cranial fossae and the frontal sinus
31
Describe what borders the inferior walls of the orbits
Maxillary sinus and palatine air cells
32
Describe the fovea ethmoidalis and its significance
The fovea ethmoidalis forms the roof of the ethmoidal sinuses and is a lateral extension of the cribtiform plate. This structure must be identified prior to lacrimal surgery to prevent inadvertent cerebral spinal fluid leakage as well as intracranial injury
33
Describe the general location of the ciliary ganglion
Approximately 1 cm in front of the annulus of Zinn on the lateral side of the ophthalmic artery between the optic nerve and the lateral rectus
34
Name the three roots of the ciliary ganglion
The ciliary ganglion recieves three roots: * A long sensory root * A short motor root * A sympathetic root
35
The ciliary ganglion recieves three roots: * A long sensory root * A short motor root * A sympathetic root Name the origin and fibers contained within the long sensory root
The long sensory root originates from the nasociliary branch of CN V1. It contains sensory fibers from cornea, iris and ciliary body
36
The ciliary ganglion recieves three roots: * A long sensory root * A short motor root * A sympathetic root Name the origin and fibers contained within the short motor root
The short motor root arises from the inferior division of CN III which also supplies the inferior oblique muscle. The fibers of the motor root synapse in the ganglion and the postganglionic fibers carry parasympathetic axons to supply the iris sphincter
37
The ciliary ganglion recieves three roots: * A long sensory root * A short motor root * A sympathetic root Name the origin and fibers contained within the sympathetic root
The sympathetic root comes from the plexus around the internal carotid artery. It enters the orbit through the superior orbital fissure within the tendinous ring, passes through the ciliary ganglion without synapse and innervates ocular blood vessels and the dilator muscles of the pupil
38
The ciliary ganglion recieves three roots: * A long sensory root * A short motor root * A sympathetic root Which fibers synapse within the ciliary ganglion?
Only the parasympathetic fibers synapse in the ciliary ganglion
39
Where are the short ciliary nerves located?
* Two groups of short ciliary nerves, totaling 6-10, arise from the ciliary ganglion. * They travel on both sides of the optic nerve * Pierce sclera around optic nerve along with long ciliary nerves * Pass anteriorly between choroic and sclera in to the ciliary muscle where they form a plexus that supplies the cornea, ciliary body, and iris
40
What types of nerve fibers make up the short ciliary nerves?
* **Nonsynapsing sympathetic fibers** (from the plexus around the adjacent ICA) (innervates ocular vessels and dilator muscles of pupil) * **Sensory fibers** (from the nasociliary nerve from CNV1) (sensation from orbit) * **Myelinated, fast-conducting postganglionic parasympathetic fibers** (from the inferior division of CNIII) (supply iris sphincter)
41
Name the seven extraocular muscles
1. Medial rectus 2. Lateral rectus 3. Superior rectus 4. Inferior rectus 5. Superior oblique 6. Inferior oblique 7. Levator palpebrae superioris
42
Name the rectus muscles in order from closest to farthest from the limbus
1. Medial 2. Inferior 3. Lateral 4. Superior
43
What is the spiral of Tillaux?
The imaginary spiral created when a curve is drawn through the insertions of the four rectus muscles on the anterior globe
44
How many millimeters away from the limbus is the insertion of the superior rectus?
7.7
45
How many millimeters away from the limbus is the insertion of the medial rectus?
5.5
46
How many millimeters away from the limbus is the insertion of the inferior rectus?
6.5
47
How many millimeters away from the limbus is the insertion of the lateral rectus?
6.9
48
Origin of EOM?
* Four rectus muscles: Annulus of Zinn * Superior oblique: Above and medial to the optic foramen on the sphenoid bone * Inferior oblique: Maxillary bone, the only extrinsic muscle to take origin from the front of the orbit; arises from a rounded tendon in a depression on orbital floor near orbital rim (maxilla) * Levator: Sphenoid bone, arises from the under-surface of the lesser wing of the sphenoid above and in front of the optic foramen
49
Inseriortion of superior oblique?
To trochlea through pulley at orbital rim then hooking back under superior rectus, inserting posterior to center of rotation
50
Insertion of inferior oblique?
Posterior inferior temporal quadrant at level of macula, posterior to center of rotation
51
What blood vessel supplies the superior oblique and superior rectus?
Superior muscular branch of ophthalmic artery
52
What blood vessels supply the inferior rectus and oblique?
Inferior muscular branch of ophthalmic artery and infraorbital artery
53
What blood vessel supplies the lateral rectus?
Lacrimal artery
54
What blood vessel supplies the medial rectus?
Inferior muscular branch of the ophthalmic artery
55
Where does the levator palpebrae superioris muscle originate?
The lesser wing of the sphenoid bone at the apex of the orbit just superior to the annulus of Zinn
56
Innervation of lateral rectus?
CN VI (abducens nerve)
57
Innervation of superior oblique?
CN IV (trochlear nerve)
58
What muscles are innervated by CN III (oculomotor nerve)?
* Upper division * levator palpebrae superioris * superior oblique * Lower division * medial rectus * inferior rectus * inferior oblique
59
Describe the different types of muscle fibers in the EOM
* **Slow** * **Tonic-type** * Unique to EOM * Smaller than twitch-type, peripheral * Innervated by multiple grape like nerves (*en grappe*) * Contracts slowly and smoothly, for smooth pursuit * **Fast, twitch-type** * **​**Similiar to skeletal muscle * Larger than tonic-type, deep in muscle * Innervated by plate like nerves (*en plaque*) * Aid in rapid saccadic movements
60
Define the palpebral fissure. Usual measurements?
The exposed zone between the upper and lower eyelids. Between 27-30 mm long Between 8-11 mm wide
61
How much vertical movement is made possible in the eyelid, and by which muscles?
Upper eyelid can be raised 15mm by levator palpebrae superioris Additional 2mm by the frontalis muscle
62
Name the layers of the eyelid from external to internal
1. Skin 2. Eyelid margin 3. Subcutaneous connective tissue 4. Orbicularis oculi 5. Orbital septum 6. Levator palpebrae superioris 7. Muller muscle 8. Tarsus 9. Conjunctiva
63
Difference in eyelid anatomy among Asians
* Few attachments of levator aponeurosis to the skin near the upper tarsal border * Superior eyelid fold minimal or absent
64
Where is the firmest attachment of the levator superioris aponeurosis?
On the anterior aspect of the tarsus approximately 3 mm superior to the eyelid margin
65
Define the *gray line*
* Along the entire length of the free margin of the eyelid is the delicate gray line or *intramarginal sulcus* * Corresonds histologically to the most superficial portion of the orbicularis oculi muscle, the muscle of Riolan, and the avascular plane of the eyelid * Anterior arise the eyelashes * Posterior are the openings of the tarsal or meobomium glands
66
Define the glands of Zeis and the glands of Moll
* **Glands of Zeis:** modified sebaceous glands associated with the follicles of cilia, holocrine, oily content * **Glands of Moll:** apocrine sweat glands in the skin, holocrine, oily content
67
Segments of the orbicularis oculi muscle?
* Arranged in concentric bands around the palpebral fissure * Subdivided into orbital, preseptal and pretarsal parts * Orbital part is purely voluntary
68
Innervation of orbicularis oculi?
Facial nerve (CN VII)
69
What muscle is encountered by the orbicularis oculi fibers at the eyelid margin?
Muscle of Riolan
70
Describe the composition of the orbital septum
* A thin sheet of conective tissue * Extension of periosteum of the roof and floor of the orbit * Attaches to the anterior surface of the levator palpebrae superioris as well as the aponeurosis * Provides a barrier to extravasion of blood or spread of infection
71
Describe the course of the levator palpebrae superioris muscle
* Originates at the lesser wing of the sphenoid * The body overlies the superior rectus muscle as it travels anteriorly towards the eyelid * Near the Whitnall ligament the levator changes direction from horizontal to vertical * Divides anteriorly into the aponeurosis which inserts into the anterior surface of the tarsus and posteriorly into the superior tarsal (Muller) muscle
72
What do the tarsal plates consist of?
Dense connective tissue (not cartilage)
73
Describe the dimensions of the tarsal plates
* Upper tarsal plates: 29mm long, 1mm thick, 11mm high * Lower tarsal plates: similar, 4mm high
74
Describe the tarsal (meibomian) glands
Modified sebaceous holocrine glands Oriented vertically in rows through the tarsus Can be observed by infrared transillumination A single row of 30-40 orifices is present in upper eyelid 20-30 in lower eyelid Oil from these forms a reservoir on the skin of the lid margin and is spread onto the tear film with each blink Aging is a/w alteration in lipid profile of meibomian gland secretions and loss of these glands
75
Describe the segments of the conjunctiva
76
Describe lymphatic drainage from the eye
* Lymphatic vessels are present in the conjunctiva and the eyelids, but not in the orbit * Two groups of lymph nodes: * Medial group that drains into the submandibular lymph nodes * Lateral group that drains into the superficial preauricular lymph nodes

Ophtho (1 decks)

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