Bone of the Skull and Orbit
What does the frontal bone make up?
Anterior portion of cranium, superior part of face, frontal sinuses, anterior floor of the cranial cavity.
The openings/holes made up from the lesser wings of the sphenoid bone. They are the passageways for the optic nerve to pass through.
Optic foramen/optic canal
This crest is located at the frontal process of the maxillary bone
anterior lacrimal crest
The most abundant amount of orbital fat is found near the
apex
What must happen to the cornea and lens as the axial length grows to get emmetropization?
as the axial length grows; the cornea and lens must lost refractive power
What causes emmetropization to occur?
blurry peripheral retinal images
Where does the internal carotid artery enter?
carotid canal of the petrous portion of the temporal bone which runs superiorly and anteriorly.
What surrounds tenon's capsule?
conjunctiva and episclera; merges w/ them anteriorly in the limbal area.
This is the superior, horizontal part of the ethmoid bone and serves a passageway for the olfactory nerves.
cribriform plate
What are some symptoms of a blowout fracture?
double vision, numbness of cheek, nose or teeth. Inability to move eyes up/down.
this is a little hole on the bottom of the maxillary bone that nerves run through from foramen and goes all the way out to the eye.
infraorbital foramen
This is the landmark for visual-evoked potential electrode placement
inion/external occipital protuberance
this forms the posterior aspect of the skull and posterior floor of cranial cavity; site of the cerebellum
occipital bone
The internal carotid artery branches off into the
ophthalmic artery
This structure covers the bones of the orbit, lacrimal gland, and lacrimal sac
periorbita/orbital periosteum/ orbital fascia
the portion of the temporal bone that extends into the cranium and houses middle/inner ear structures.
petrous portion
Where is the foramen spinosum found?
posterior and temporal to the foramen ovale
Where is the foramen ovale located?
posterior and temporal to the foramen rotundum
The _______ projects from the base of the greater wing and articulates with the vertical stem of the palatine bone; each contributes to a shallow depression, the pterygopalatine fossa.
pterygoid process
What does the foramen rotundum communicate with?
pterygoidpalatine fossa and inf orbital fissue
What is located at the pterygoid palatine/fossa?
pterygoidpalatine nerve and ganglion
Where is the Suspensory Ligament of lockwood?
runs between lacrimal bone on medial wall to the zygomatic bone on the lateral wall
Where does the facial nerve exit?
stylomastoid foramen in the petrous portion of the temporal bone
This is the gap between the greater and lesser wings of the sphenoid bone; located between roof and lateral wall.
superior orbital fissure
gap between greater and lesser wings of sphenoid; multiple nerves and arteries pass through
superior orbital fissure
What is the mandibular nerve a branch of and where does it innervate?
trigeminal, sensory and motor of lower face
What makes up the floor of the orbit?
- small orbital process of palatine bone -orbital surface of maxillary bone (majority) - orbital plate zygomatic bone
What is the average axial length of an adult emmotropic eye? How does it differ in hyperopes and myopes?
-Avg axial length; 23-24 mm. -myopes tend to have longer axial lengths while hyperopes tend to have shorter ones
Name 3 important functions of the optic foramen/optic canal.
-Communication between orbital cavity and middle cranial fossa -Entry way for ophthalmic artery to supply blood to the eyes -Exit way for the optic nerve to go from retina to brain
What can happen to the orbital septum w/ age? how about the paranasal sinuses?
-Orbital septum: weakens; can cause herniation of loose fat and CT esp in the inferior medial area -paranasal sinuses; thin out
What is the periorbita continuous with?
-Periosteal covering of facial bones and skull -Orbital septum @ orbital margins -Dura of optic nerve -Common tendinous ring -Tissue lining of nasolacrimal canal
What are the main functions of the orbital spetum?
-prevent infections from entering the orbit -keeps orbital fat in place
What is the function of the orbital septa system?
-slings that anchor and support extraocular muscles and blood vessels to orbital wall -maintains position of muscles during eye movement.
Name the 11 bones of the orbit (note: some are duplicates)
1. Frontal bone 2.Ethmoid bone 3. Lacrimal bone (2) 4. Palatine bone (2) 5. Maxillary bone (2) 6. Zygomatic bone (2) 7. Sphenoid bone
name 4 functions of orbital CT.
1. Lines, covers, and separates orbital structures 2. anchors soft tissue structures to bone 3. compatermentalizatiton 4. Compact w/ contents
Name the 7 important components of the greater wings of the sphenoid bone.
1. Superior orbital fissure 2. Foramen rotundum 3. Foramen ovale 4. Foramen spinosum 5. Pterygopalatine fossa 6. Pterygopalatine canal 7. Pterygoid process
What are 3 main characteristics of sinuses?
1. air filled and mucous lined 2. small apertures that communicate w/ the nasal cavity 3. thin walls which are prone to infection and fracture
Whitnall's tubercle is the site for the following:
1. aponeurosis of superior palpebral levator muscle 2. lateral palpebral ligament (keeps tarsal plate and lid margin against the globe) 3. lateral rectus check ligament (keeps EOMs in check) 4. suspensory ligament of Lockwood 5. orbital septum
What are the functions of the periorbita?
1. attachment site for muscles, tendons, and ligaments 2. supports the structure for blood supply to bones 3. Loosely attached to underlying bones except for the orbital margins; sutures; and edges of fissures/foramina
Branches of the maxillary nerve provide sensory information to the follow areas:
1. conj 2. lower lid 3. cheeks 4. upper lip 5. palate 6. teeth 7. maxillary sinus
1. The orbital septum is continous w/ 2. Blends w/ the ______ in the upper lid 3. Merges w/ ______ & _____ in the lower lid
1. periosteum 2. levator aponuerosis 3. tarsal plate and CT
Name 4 key characteristics of a myopic eye.
1. thinner sclera 2. existing collagen breaks down/proteoglycans are lost 3. scleral ectasia may occur in high myopes where the posterior globe bulges backward 4. weaker by up to 40% mechanically
What is the average size of an optic nerve head?
1.5 mm
What is the average depth of a fully grown orbit? how much does the eye occupy?
45 mm; 25%
This structure is located anterior to the superior orbital fissure and optic canal; it is the site of attachment for 4/6 extraocular muscles.
Common tendinous ring/Annulus of Zinn
The entire body of the ethmoid bone has these hollow mucous lined passageways. What are these called?
Ethmoid sinuses
True or false: The medial wall is the "thinnest" of the four walls and the most susceptible to fractures.
False; although the medial wall is the thinnest it is not most susceptible to fractures because it is mostly protected. The floor is most susceptible to fractures.
True or false: the globe is perfectly spherical
False; it is about 23 mm vertically and 23.5 mm horizontally
Which orbital wall is the weakest? What is it susceptible to? Which portion is most susceptible
Floor; blow-out fractures. Thin region around infraorbital canal.
Where does the orbital septum attach laterally?
Front of palpebral lacrimal crest on the lateral margin; including Whitnall's tubercle (which is on the zygomatic bone)
Where does the frontal lobe sit?
In the anterior cranial fossa.
Where do the frontal sinuses sit? What is their relationship to the eyes?
In the anterior portion of the frontal bone. The sinuses sit very close to the eyes.
A passageway for the infraorbital nerve, artery and vein found in the inferior orbital margin (hint: it is formed by the floor of the orbit)
Infraorbital foramen/canal
__________ runs across the floor from the inferior orbital fissure and anteriorly is bridged by a thin plate of bone, thus becoming a canal running within the maxillary bone. This canal opens on the facial surface of the maxilla below the inferior orbital margin as the _________.
Infraorbital groove and foramen
Where does the septum specifically branch out? Why does it do this?
Into the lacrimal sac region; it goes posterior and anterior and then wraps around the lacrimal sac because this prevents lacrimal sac infection from entering into the lids and orbit
How can a tumor in the pituitary gland cause vision loss?
It can push against the optic nerve and cause a vision deficit in the region where there is nerve supplies for vision.
If there is no visual stimulation (ie: in a blind eye)/ extreme muscle relaxation, what happens to the eye?
It will not look forward
What are the 3 bones of the nasolacrimal system?
Lacrimal bone and maxillary bone (crests), inferior nasal concha
What makes up the medial wall of the orbit?
Mainly the ethnoid bone but also frontal process of maxilla, lacrimal bone, body of sphenoid
What bones make up the medial orbital margin? What does this margin form?
Maxillary and frontal; forms the groove for the lacrimal sac
what bones make up the inferior orbital margin?
Maxillary and zygomatic (maxillary process of zygomatic bone and zygomatic process of maxillary bone)
What is the pterygoidpalatine nerve and ganglion a branch of? What does it innerate?
Maxillary nerve, inntervates lacrimal gland and nasal mucoas
Why does the septum have holes?
Nerves and blood vessels run through it
What can happen if the roof of the orbital wall resorbs w/ age?
ONLY periosteal tissue will separate the dura mater of the frontal lobe from the globe.
Why is it especially important for the zygomatic bone to be strong?
People are post likely to get hit here.
What structure of the sphenoid bone is at the midline? What important structure is housed here and what is the structure called?
Sphenoid body; pituitary gland in hypophyseal fossa/sella turcica.
single bone, the body of which lies in the midline and articulates with the occipital bone and the temporal bones to form the base of the cranium. Makes up _____ wall of the orbital.
Sphenoid bone, lateral
This notch is well-defined, located medially, and is a conduit/channel for - vessels and nerves (provide sensory info from forehead)
Supraorbital notch
Tissues from the following structures make up the tissues for the suspensory ligament of lockwood:
Tenon's, sheaths of inferior EOMs, inferior eyelid aponeurosis
What would happen if there was no medial rectus muscle?
The eyes would remain in their "resting position" and diverge outwards; the medial rectus muscle pulls the eyes in by 23º
Orbit is very compact w/ contents; what can happeb if a space-occupying lesion were to enter?
They can damage the optic nerve and/or cause outward displacement of the globe.
Where does the orbital septum attach medially?
To posterior lacrimal sac; just behind the lacrimal sac and medial palpebral ligament
What is the maxillary nerve a branch of?
Trigeminal nerve
When a blow-out fracture occurs, where does pressure move?
downward
What does the middle meningeal artery supply?
dura mater and facial nerve (which is important for lid muscles)
What does tenon's capsule merge w/ posteriorly?
dura sheath of the optic nerve
The process by which the cornea, lens, and axial length make coordinated changes as the eye grows in order to keep the retinal image of a distant object in sharp focus
emmetropization
which sinuses are most likely to cause eye pain and why?
ethmoid and sphenoid bc of their close proximity to the optic nerve.
A very thin bone that make up medial portion of the eye socket.
ethmoid bone
This sinus has multiple air pockets on the medial sides of both orbits; sometimes it communicates w/ lacrimal bone/maxilla and other times w/ dura sheath of optic nerve
ethmoid sinus
What parts of the orbit is the maxillary bone a part of?
floor and medial wall of orbit
this fossa is formed by the posterior and anterior lacrimal crests. This indentation is where the frontal, maxilla, and lacrimal bones come together.
fossa for lacrimal sac
This type of sinus is above the orbit which 1 sinus on each side of the midline.
frontal
What makes up the roof of the orbit?
frontal bone and lesser wing of sphenoid
What are the parts of the superior orbital margin?
frontal bone, supraorbital notch, supratrochlear notch
What are the four paranasal sinuses?
frontal, ethmoid, sphenoid, maxillary
Why is the optic nerve kinked?
gives extra room incase eye bulges outward
What does the roof of the orbit separate?
globe from dura of frontal lobe
project from the lateral aspects of the spenoid body and articulate with the frontal bone, the parietal bones, squamous portions of the temporal bones, and the zygomatic bones.
greater wings of the sphenoid bone
This fissure is the gap between maxillary and sphenoid bones. The floor does not reach all the way to the apex and is separated from the lateral wall posteriorly by this fissure.
inferior orbital fissure
What structures are formed by the floor of the orbit?
inferior orbital fissure, infraorbital groove, infraorbital canal, infraorbital foramen
What is the function of the medial palpebral ligament/tendon?
keeps tarsal plate and lid margin against globe; if it stretches out then the it may cause an ectroprian/epiphra
smallest bone of the face and articulates with the maxillary bone, ethmoid bone, and frontal bone.
lacrimal bone
What important fossa is located at the roof of the orbit?
lacrimal fossa
This is a small, bony prominence on orbital surface of zygomatic bone found in the lateral wall
lateral or marginal tubercle/Whitnall's Tubercle
In the superior orbital fissure, there is an attachment site for the lateral rectus muscle.
lateral rectal spine
Two pairs of wings project from the body of the sphenoid bone. The ______ wings project from the anterior aspect of the body and are more superior.
lesser
What part of the orbit is the frontal bone a part of?
majority of the roof of the orbit.
What nerve passes through the foramen ovale?
mandibular nerve
What froms the stylomastoid foramen?
mastoid and styloid processes
The eye's CT is in really close contact w/ multiple sinuses in the _____ bone.
maxillary
What nerve passes through the foramen rotundum? Where is it found?
maxillary nerve; posterior to the orbital fissure
Which sinus is most significant in a blowout fracture?
maxillary sinus
This ligament/tendon attaches to both the anterior and posterior lacrimal crest.
medial palpebral ligament/tendon
The _______ walls run parallel to each other; the ______ wall forms 90º angle
medial; lateral
What passes through the foramen spinosum?
middle meningeal artery
This canal is continuous w/ the fossa for the lacrimal sac and with the nasal cavity.
nasolacrimal canal
The bony socket on either side of the midline that houses the globe, extraocular muscles, and other CT. It also serves an attachment point for muscles. How many bones make up this structure?
orbit; 11 bones
The superior orbital fissure serves as a communication between the...
orbital cavity and middle cranial fossa
What is an example of a sinusitis condition that may cause eye pain, pressure, and infection?
orbital cellulitis
In the orbit, any space that is not occupied by anything is occupied by?
orbital fat
What part of the ethmoid bone makes up the medial wall of the orbit?
orbital plates
a complex web of interconnecting tissue septa surrounding the globe; the collagenous strands connect the periorbita to Tenon's/Intermuscular mem
orbital septa system
this is a thin, multilayered, fibrous membrane that forms the anterior boundary of the orbit
orbital septum
This bone makes up a very tiny portion of the orbit. It extends from the hard palate to the back of the mouth. It also extends vertically thru the nasal cavity and into the orbital floor.
palatine bone
This crest is located at the lacrimal bone
posterior lacrimal crest
an inflammation or swelling of the tissue lining the sinuses. What are the implications w/ the eyes in minor and severe cases?
sinusitis; in minor cases: eye pain in major cases: optic nerve damage
A sinus within body of this bone. It is posterior and medial to both orbits. In some people this sinus actually surrounds the optic nerve
sphenoid sinus
This is the hollow portion of the body of the sphenoid body.
sphenoid sinus
Name the two portions of the temporal bone
squamous and petrous portion
the portion of the temporal bone that is at the side of the cranium
squamous portion
This notch is not well defined, in the superior medial corner, and is a passageway for - vessels and nerves. (supply blood and take sensory info from forehead)
supratrochlear notch
This ligament acts as a hammock to support the globe inferiorly
suspensory ligament of Lockwood
This structure encases the globe and prevents orbital infections from entering the globe.
tenon's capsule
Like the orbital septum, what makes tenon's capsule weak?
the optic nerve and BVs that run through it
This is located in the roof of the orbit about 2 mm behind superior orbital margin and acts as a pulley structure of the superior oblique muscle
trochlea
What is part of the maxillary bone? Does it have sinuses?
upper jaw, hard palate, nasal cavity. It has large sinuses in the cheek area.
What bones make up lateral wall?
zygomatic and greater wing of the sphenoid bone
This bone makes up the cheekbones and lateral wall of orbit. Articulates w/ frontal, sphenoid, maxillary, and temporal bones
zygomatic bone
What bones make up the lateral orbital margin?
zygomatic process of frontal and frontal process of zygomatic
What suture is found and can be palpated @ the inferior orbital margin?
zygomaticomaxillary suture
When does the orbit become full size?
age 16
