Orbital Anatomy Flashcards
What are the orbital walls
- orbital roof
- lateral wall
- floor
- medial wall
What are the bones of the roof of the orbit?
Frontal
Sphenoid
What are the bones of the lateral wall of the orbit?
Sphenoid
Zygomatic
What are the bones of the floor of the orbit?
Maxillary
Palatine
Zygomatic (MPZ)
What are the bones of the medial wall of the orbit?
Sphenoid Lacrimal Ethmoidal Maxillary (SLEM)
What are the bones of apex of the orbit?
Mostly comprised of the greater and lesser wings of the sphenoid bone
Where is the superior orbital fissure?
Roof of orbit
Where is the ethmoid sinus in relation to the orbit?
Medial to medial wall
What is the most dangerous sinus?
Sphenoid sinus
Where does the sphenoid sinus lie?
Adjacent to optic nerve and optic canal
Why is the sphenoid sinus dangerous?
Infection could cause blindness
Expansion of the sphenoid sinus compresses optic nerve bilaterally and can cause blindness
Sphenoid sinusitis
What is the thinnest bone of the orbit and where is it located?
Ethmoid bone in the medial wall
Where does the lacrimal sac reside?
Lacrimal fossa
What is the a link for some of the pathology for orbital cellulitis?
Vessels that go through the foramen in the anterior and posterior ethmoidal foramen
Where are the anterior and posterior ethmoidal foramen?
Medial wall
What is the second weakes bone of the orbit?
Floor bones: maxillary sinus underneath, fissures, and foramen
What makes the floor a susceptible place for trauma?
Thin bone, maxillary sinus underneath, fissures and foramen
What are the sinuses that surround the orbit?
-maxillary, frontal, sphenoid
What sinus us between the orbits?
Ethmoid sinus
What fissures are in the posterior orbit?
- superior orbital fissure
- inferior orbital fissure
- optic canal
What are the foramen and fissures in the anterior orbit?
- supraorbital and infraorbital fissures
- zygomatical and zygomaticotemporal fissures
What is the sensory foramen for sensation to the eyelid and face
Zygomaticofacial and zygomaticotemporal
What is the lateral wall for lateral face?
Zygomaticofacial and zygomaticotemporal fissures
Importance of fissures and foramen
They are where the bones of the orbit connect=weak spots in the orbit
-acts as places for infection to spread and come into orbit
Reasons orbital fractures may occur
- closed compartment
- limited space (shock waves from hitting orbital rims)
- weak spots (fissures and foramen)
Major foramen in orbital apex
- supraorbital fissure
- infraorbital fissure
- foramen rotundum
- optic canal
What is the back where everything connects in the back of the orbit called?
Annulus of Zinn
What are the nerves that are outside the annulus of zinn?
- lacrimal nerve
- frontal nerve
- trochlear nerve (CN IV)
Luscious French tarts
Nerves inside the annulus of zinn
- superior division of oculomotor nerve (CN III)
- nasociliary nerve
- inferior divions of oculomotor nerve (CNIII)
- abducens nerve (CN VI)
Standing naked in anticipation
Thyroid eye disease
Can cause muscles to swell in back in the apex and can crush vital structures, can cause motility problems and blindness
Fixed structure in the optic canal
Optic nerve
Blunt trauma and the optic nerve
Can stretch the optic nerve or cut off blood supply to cause indirect optic nerve injury and blindness
Outer ring of EOMs
- levator palpebrae (eyelid
- superior oblique (torsion)
- inferior oblique (torsion)
What is the function of the superior oblique
Torsion
What is the most superior EOM?
Lavator palpebrae
What is the third superior EOM?
Superior oblique
Where does the superior oblique attach?
Trochlea
What is the action of the inferior oblique
Torsion
What does the inner ring of EOMs consist of?
- superior rectus
- inferior rectus
- medial rectus
- lateral rectus
What is the second most superior EOM
Superior rectus
What EOM attaches at the lacrimal fossa?
Inferior rectus
What happens in thyroid eye disease?
-muscles swell and get enlarged in back of eye
How can you release pressure in someone with thyroid eye disease?
Making room in the orbit by removing ethmoid bone or ethmoidal tissue
What is usually the first EOM impacted by thyroid eye disease?
Inferior rectus
What are some characteristics of thyroid eye disease?
Dry eye and upper lid retraction
What are the motor nerves of the eye?
CN III, IV, and VI
What muscles does CNIII innervate?
- levator palpebrae
- superior rectus
- medial rectus
- inferior rectus
- inferior oblique
What muscles does CN IV innervate?
Superior oblique
What muscle does CN VI innervate?
Lateral rectus
What are the sensory nerves of the eye
- nasociliary
- zygomaticotemporal
- zygomaticofacial
- infraorbital
What does the nasociliary nerve innervate?
Nose
Hutchinson’s sign
In shingles, this indicates an impact on nasociliary nerve and a more likely infection with the eye due to relation with muscles
What does the zygomaticotemporal and zygomaticofacial nerves innervate?
Lateral face
What does the infraorbital nerve innervate?
Cheek and face
What artery gives access to cavernous sinus?
Supraorbital artery
What allows infection to spread through the ethmoid foramen?
Anterior ethmoid artery
Blood supply for the eyelid branches off of what?
The facial artery
Where do veins of the face begin?
Cavernous sinus
What are veins susceptible to that beceom enlarged and cause eye to bulge
Varicoel
Why are veins a pathway for infection?
Due to communication with each other
Orbit is what kind of compartment?
Closed. Muscles and blood supply are surrounded by soft tissue to limit their expansion. Diseases or swelling in one area can have impact on the structures immediately adjacent to them
Kids and infections
Anything that happens in kids happens faster and is more dangerous
If there is no up gaze or down gaze, what is it most likely caused by?
Orbital cellulitis
Canthal tilt
Can be indication of underlying pathology
Asians eyelids
Absence of lid fold because of attachments underneath the orbicularis muscle, important in ptosis and disrupting lid folds
Main CT structures giving giving structure and function to the eyelids
Tarsal plates
Divides to go in front and behind lacrimal fossa
Medial canthal tendon
What helps direct tear drainage and distribution
Tendons
What muscles are the protractors of the eyes?
Orbicularis muscles
Where does the orbicularis muscles attach?
Nasally
What are the eyelid openers?
Lavator palpebrae superioris and others
What muscle results in droopy eyelid and blocks vision
Lavator palpebrae superioris
What is often the thing that gets stretched in the eyelids
Aponeurosis connecting muscle to tarsal plate
Which eyelid is not very mobile?
Lower eyelid
What muscle is used for porlonged opening of the eye?
Mueller muscle
What are the fat compartments of the orbit?
- 2 fat pads on top (not temporal)
- 3 pads on bottom
Why is it important to remember that the eyelids are connected to res to the face?
For things like Shingles
What are the protractor muscles innervated by?
Facial nerve
What is the paralysis of the face often related to?
Bells Palsy of facial nerve
What is the secretory system of the eye?
Components of the tear film
In superior lateral aspect of the orbit. Mostly responsible for aqueous portion of the tear film
Lacrimal gland
Where is the lacrimal gland located
Superior lateral aspect of orbit, lacrimal gland fossa
What is the lacrimal gland sometimes confused for?
Fat pad
Responsible for distributing tear film across the cornea and into the excretory system
Distributors system
Drainage system of eye
Excretory system
Tiny holes in each lid
Puncta
First point of entrance for tears into the excretory system
Puncta
How does the puncta take in tears?
When eyes close, puncta tune in and Crete negative pressure so when eyes open, the pressure sucks in the tears
Position of puncta
Has to be properly immediately in and adjacent to the eye
Tear flow to canaliculus
Tears go to vertical canaliculus and then to the horizontal canaliculus
What makes the common canaliculus
Two horizontal canaliculus join to form this
Pathway of tears
- puncta to canaliculus
- canaliculus to common canaliculus
- common canaliculus to lacrimal sac
- lacrimal sac narrows into the nasolacrimal duct which then enters the nose in the inferior meatus
- tears exit through Hasner’s Valve
Where do tears exit
Hasners valve
What is the most common thing that can mess up the system of tear flow?
Makeup
How does makeup mess up the flow of tears?
Makeup and mucus combine to make stones and block the drain
Why do babies tears build up sometimes
Hasner’s valve is the last thing to develop in babies, so their tears can build up. Usually resolves itself
How can ptosis affect tear flow?
Can cause puncta not to separate and stop tears from draining
