The Orbital Cabity Flashcards
What are the orbital cavities?
A pair of large bony sockets that contain the eyeballs, associated muscles, nerves, vessels, fat, and most of the lacrimal apparatus.
What shape are the orbital cavities? Which direction do they point in?
Pear-shaped with the apex directed posteriorly, medially, and slightly upward.
How many bones form the orbit?
Seven bones: maxilla + palatine, zygomatic + sphenoid, frontal, ethmoid, and lacrimal.
Describe the shape of the orbital margin.
Quadrilateral with rounded corners.
Is the orbital margin wider than it is high in adults?
Yes.
Which bone forms the supraorbital margin? - describe features
Frontal bone. Lateral 2/3 sharp, medial 1/3 rounded. Supraorbital notch at intersection.
What is the function of the supraorbital notch or foramen?
Passage of the supraorbital vessels and nerve.
Which bones form the infraorbital margin?
Laterally by zygomatic bone and medially by maxilla.
What is the strongest part of the orbital margin? What is it formed by (be specific)
The lateral margin, formed by the frontal process of the zygomatic bone and the zygomatic process of the frontal bone.
What forms the medial margin of the orbital cavity? (be specific)
Above by the maxillary process of the frontal bone and below by the lacrimal crest of the frontal process of the maxilla.
What are the walls of the orbital cavity lined with?
Periosteum.
Where is the apex of the orbital cavity located?
At the medial end of the superior orbital fissure.
What forms the roof of the orbital cavity?
Orbital plate of the frontal bone and lesser wing of the sphenoid.
What is the lacrimal fossa?
A slight depression for the orbital part of the lacrimal gland located anterolaterally on the roof of the orbit.
What separates the orbital cavity from the anterior cranial fossa?
The roof of the orbit.
What happens to the roof of the orbit in old age?
Portions of the roof may be absorbed.
Where is the depression/spine for the attachment of the pulley of the superior oblique muscle located?
Medially to the supraorbital notch and 4mm behind orbital margin
True or False: The roof of the orbit is thick and robust.
False. Thin _ fragile.
What forms the thin floor or inferior wall of the orbital cavity?
1) The orbital plate of the maxilla
2) the orbital surface of the zygomatic bone
3) small orbital process of the palatine bone
These bones contribute to the structural integrity of the orbital floor.
What does the orbital plate of the maxilla separate?
The orbital cavity from the maxillary sinus
This separation is important for the functioning of both anatomical structures.
How is the floor of the orbital cavity related to the lateral wall?
The floor is continuous with the lateral wall anteriorly but separated by the inferior orbital fissure posteriorly
This anatomical relationship is crucial for understanding the layout of the orbit.
What runs forward from the inferior orbital fissure?
The infraorbital groove
The infraorbital groove is a key pathway for nerves and blood vessels.
What does the infraorbital groove become at about the midpoint of the floor?
The infraorbital canal
The canal serves as a passageway for the infraorbital nerve and vessels.
What does the infraorbital canal open onto the face as?
As the infraorbital foramen
The foramen provides access for the infraorbital nerve to the facial region.
What is the thickest wall of the orbit?
Lateral wall
The lateral wall is the thickest wall of the orbit.
Which bone forms the anterior third of the lateral wall?
What does it separate the orbit from?
Zygomatic bone
The zygomatic bone separates the orbit from the temporal fossa.
What forms the posterior two-thirds of the lateral wall?
What does it separate the orbit from?
Greater wing of the sphenoid bone
It separates the orbit from the temporal lobe of the brain in the middle cranial fossa.
What structure separates the lateral wall and roof posteriorly?
Superior orbital fissure
Lateral wall and roof of orbit are continuous anteriorly
The superior orbital fissure communicates with the middle cranial fossa.
Where is the marginal tubercle located?
Just posterior to the orbital margin on the frontal process of the zygoma
The marginal tubercle is a small prominence.
What attaches to the marginal tubercle?
1) Aponcurosis of the levator palpebrae superioris
2) lateral palpebral ligament
3) lateral check ligament
These structures attach from before backward.
Fill in the blank: The anterior third of the lateral wall is formed by the _______.
Zygomatic bone
True or False: The lateral wall and roof are continuous anteriorly.
True
What are the four bones that form the medial wall of the orbit?
1) Frontal process of the maxilla
2) lacrimal bone
3) orbital plate of the ethmoid
4) body of the sphenoid
These bones are arranged from anterior to posterior.
Which bone forms the largest part of the medial wall of the orbit?
Orbital plate of the ethmoid
The orbital plate is almost rectangular in shape and very thin.
What does the ethmoid bone separate the orbit from?
Separates the orbital cavity from the ethmoidal sinuses
This separation is crucial for the integrity of the orbit and the sinuses.
What is located on the anterior part of the medial wall?
Lacrimal groove for the lacrimal sac
This groove aids in the drainage of tears.
The lacrimal groove is formed by which two bones? (be specific)
Lacrimal bone posteriorly
frontal process of the maxilla anteriorly
The groove is bounded by the anterior and posterior lacrimal crests.
What structure is continuous with the lacrimal groove and leads into the nasal cavity?
Nasolacrimal canal
The nasolacrimal canal allows for tear drainage into the nasal cavity.
True or False: The medial wall of the orbit is thick and robust.
False
The medial wall is described as very thin.
What is the shape of the orbital plate of the ethmoid?
Almost rectangular
This shape contributes to its structural characteristics.
Fill in the blank: The _______ forms the anterior boundary of the lacrimal groove.
Frontal process of the maxilla
This anatomical feature is important for lacrimal sac positioning.
Fill in the blank: The _______ connects the lacrimal groove to the nasal cavity.
Nasolacrimal canal
This connection is vital for tear drainage.
Where is the optic canal located?
What is the optic canal related to medially?
The lesser wing of sphenoid
The body of the sphenoid.
True or False: The optic canal is situated far from the apex of the sphenoid.
False.
What structures form the roof of the orbit?
Orbital plate of frontal bone, lesser wing of sphenoid
The roof is crucial for protection and support of the orbital contents.
What structures form the floor of the orbit?
Orbital plate of maxilla, orbital surface of zygomatic, orbital process of palatine
The floor supports the orbital contents and separates the orbit from the maxillary sinus.
What structures form the lateral wall of the orbit?
Zygomatic, greater wing of sphenoid
This wall provides lateral support and protection to the eye.
What structures form the medial wall of the orbit?
Frontal process of maxilla, lacrimal bone, orbital plate of ethmoid, body of sphenoid
The medial wall is thin and includes structures related to the nasal cavity.
What is the function of the optic canal?
Transmits the optic nerve (+its sheet of meninges and subarachnoid space) and ophthalmic artery
The optic canal connects the middle cranial fossa with the orbital cavity.
How long is the optic canal?
4-10mm long
What is the first branch of the internal card artery after it leaves the cavernous sinus?
Ophthalmic artery
Where is the superior orbital fissure located?
Between the lesser and greater wings of the sphenoid
It connects the middle cranial fossa with the orbital cavity.
What passes through the superior orbital fissure?
From lateral to medial:
Outside common tendinous ring:
- Lacrimal nerve
- Frontal nerve
- Superior ophthalmic vein
- Trochlear nerve
*inferior ophthalmic vein
Within common tendinous ring:
* Oculomotor nerve (upper and lower divisions)
* Nasociliary nerve
* Abducent nerve
The fissure is also associated with the common tendinous ring for rectus muscles.
What does the inferior orbital fissure connect?
Where is the inferior orbital fissure found?
Pterygopalatine and infratemporal fossae with the orbital cavity
It transmits the maxillary nerve, which changes to the infraorbital nerve.
Found between greater wing of sphenoid and maxilla
What structures are transmitted through the inferior orbital fissure?
- Maxillary nerve - becomes called infraorbital nerve
- Zygomatic nerve
- Branches of pterygopalatine ganglion
- Inferior ophthalmic vein
The inferior ophthalmic vein drains into the pterygoid venous plexus.
Inferior orbital fissure is closed in living subjects by the periorbita + muller’s muscle
What is the function of the anterior ethmoidal foramen?
Where is it found
Transmits the anterior ethmoidal nerve and artery
It opens into the anterior cranial fossa. lies in frontoethmoidal suture - opens into anterior cranial fossa at lateral edge of cribriform plate of ethmoid bone
What does the posterior ethmoidal foramen transmit?
Where is it found
Posterior ethmoidal nerve and artery
These supply the ethmoidal sinuses. Transverses ethmoid bone
Where are the zygomaticofacial and zygomaticotemporal foramina located?
On the lateral wall of the orbit. zygomaticofacial = close to junction of lateral wall and floor, zygomaticotemporal lies just above this.
These foramina transmit the zygomaticofacial nerve and zygomaticotemporal nerve respectively.
The zygomaticofacial foramen transmits which nerve?
Zygomaticofacial nerve
It is located near the junction of the lateral wall and floor of the orbit.
The zygomaticotemporal foramen lies above which foramen?
Zygomaticofacial foramen
It is close to the sphenozygomatic suture.
What forms the roof of the bony orbit?
The orbital plate of the frontal bone
Contains the frontal air sinus and occasionally the ethmoid air cells.
What lies inferior to the floor of the bony orbit?
The maxillary air sinus
Also contains the infraorbital nerve and blood vessels within the infraorbital canal.
What separates the orbital cavity from the temporal fossa anteriorly?
The lateral wall
It also separates the orbital cavity from the middle cranial fossa posteriorly.
What structures are separated by the medial wall of the bony orbit?
The nasal cavity, ethmoidal sinuses, and sphenoid sinus
This separation occurs from anterior to posterior.
What is the periorbita?
The periosteum of the bones that form the walls of the orbit
It is loosely attached to the bones and continuous with the periosteum covering the outer surfaces.
What generally happens to the periorbita at the orbital fissures?
It becomes continuous with the endosteal layer of the dura mater.
At foramen, it generally remains adheseve to bone.
At optic canal, it attaches to the dural sheath of the optic nerve
What is the common tendinous ring?
A fibrous ring formed by the thicker periorbita around the optic canal and medial end of the superior orbital fissure
It gives origin to the tendons of the four rectus muscles.
What provides sensory innervation to the periorbita?
Branches of the trigeminal nerve
These branches lie within the orbital cavity.
Fill in the blank: The periorbita becomes continuous with the periosteum on the external surface of the skull at the _______.
orbital margin
True or False: The periorbita is tightly attached to the bones of the orbit.
False
The periorbita is loosely attached to the bones.
What does the periorbita enclose at the lacrimal groove?
The lacrimal sac
It continues inferiorly to form the periosteum of the nasolacrimal canal.
What is the relationship between the periorbita and the eyelids?
It gives rise to sheets that enter the eyelids to form the orbital septum.
What structures are located superior to the roof of the bony orbit?
The meninges and the frontal lobe of the cerebral hemisphere.
What is the orbital muscle also known as?
Muscle of Müller
The orbital muscle is a thin layer of smooth muscle bridging the inferior orbital fissure.
What is the function of the orbital muscle (aka muscle of muller) ?
Unknown
The orbital muscle is regarded as a vestigeal muscle.
What type of nerve supply does the orbital muscle (aka muscle of muller) receive?
Sympathetic nerves
How do the orbital cavities change from birth to old age?
Bony absorption occurs, resulting in holes in the orbital walls
At birth, the orbital cavities are large and ossified, but they change with age.
What happens to the orbital fissures as a child grows?
They become narrower
The superior and inferior orbital fissures are wider in a child and narrow with the growth of the greater wing of the sphenoid.
What sex differences are observed in the orbital cavities after puberty?
Female orbits remain rounder and bones are smoother than in males
Where are the superciliary ridges located?
Above the upper margin of the orbit
Where does the medial end of the eyebrow lie in relation to the supraorbital margin?
Below the medial end of the supraorbital margin
Which bones form the orbital margins?
Frontal, maxillary, and zygomatic bones
What anatomical feature can be palpated at the junction of the medial third and lateral two-thirds of the superior margin?
Supraorbital notch
The supraorbital nerve can sometimes be rolled in the notch.
Where can the trochlea of the superior oblique tendon be felt?
Within the superomedial part of the orbital margin
What structure can be felt between the lateral bony margin of the orbit and the lateral end of the palpebral fissure?
Lateral palpebral ligament
What can be felt between the medial bony margin of the orbit and the palpebral fissure?
Medial palpebral ligament
Which anatomical landmarks can be felt along the medial part of the orbital margin?
Anterior lacrimal crest, lacrimal groove, posterior lacrimal crest
Where is the infraorbital foramen located?
About 5 mm below the lower margin of the orbit
What is the orbital muscle also known as?
Muscle of Müller
The orbital muscle is a thin layer of smooth muscle bridging the inferior orbital fissure.
What is the function of the orbital muscle?
Unknown
The orbital muscle is regarded as a vestigeal muscle.
What type of nerve supply does the orbital muscle receive?
Sympathetic nerves
How do the orbital cavities change from birth to old age?
Bony absorption occurs, resulting in holes in the orbital walls
At birth, the orbital cavities are large and ossified, but they change with age.
What happens to the orbital fissures as a child grows?
They become narrower
The superior and inferior orbital fissures are wider in a child and narrow with the growth of the greater wing of the sphenoid.
What sex differences are observed in the orbital cavities after puberty?
Female orbits remain rounder and bones are smoother than in males
Where are the superciliary ridges located?
Above the upper margin of the orbit
Where does the medial end of the eyebrow lie in relation to the supraorbital margin?
Below the medial end of the supraorbital margin
Which bones form the orbital margins?
Frontal, maxillary, and zygomatic bones
What anatomical feature can be palpated at the junction of the medial third and lateral two-thirds of the superior margin?
Supraorbital notch
The supraorbital nerve can sometimes be rolled in the notch.
Where can the trochlea of the superior oblique tendon be felt?
Within the superomedial part of the orbital margin
What structure can be felt between the lateral bony margin of the orbit and the lateral end of the palpebral fissure?
Lateral palpebral ligament
What can be felt between the medial bony margin of the orbit and the palpebral fissure?
Medial palpebral ligament
Which anatomical landmarks can be felt along the medial part of the orbital margin?
Anterior lacrimal crest, lacrimal groove, posterior lacrimal crest
Where is the infraorbital foramen located?
About 5 mm below the lower margin of the orbit
What is the relationship between the bony orbit and the eyeball?
The bony orbit is a closed socket for the eyeball, with limited space between the orbital walls and the eyeball causing quick proptosis from expanding lesions.
Proptosis is the protrusion of the eyeball, which can occur due to various conditions affecting the orbit.
What effect does enucleation of the eye in a child have on orbital growth?
It results in impaired future growth of the orbit.
Enucleation refers to the surgical removal of the eye.
What may congenital abnormalities of the skull lead to in relation to the orbit?
They may be associated with exophthalmos and strabismus.
Exophthalmos is the protrusion of the eyeball, and strabismus refers to misalignment of the eyes.
What are some congenital conditions that can affect the orbit?
Craniosynostosis, mandibulofacial dysostosis, developmental tumors, meningocele, and encephalocele.
These conditions can lead to structural abnormalities in the orbit and surrounding areas.
How strong is the orbital margin and what can cause fractures?
The orbital margin is very strong, but severe injuries, such as those from automobile accidents, can cause fractures.
Fractures may involve the medial margin and the nose.
What symptoms can arise from fractures of the superior margin of the orbit?
They may damage or displace the trochlea, producing symptoms of superior oblique paralysis.
The trochlea is a pulley-like structure that helps in eye movement.
What is a blow-out fracture?
It is a common result of blunt force to the face, affecting the floor and medial wall of the orbit.
Blow-out fractures occur due to the thinness of the bones in these areas.
What happens to the prominence of the cheek in fractures involving the zygoma?
It results in depression of the prominence of the cheek.
The zygoma, or cheekbone, is a key structure in the facial skeleton.
Fill in the blank: The _______ are the thinnest bones in the orbit.
floor and medial wall.
These regions are particularly vulnerable to fractures.
What is the significance of the supraorbital notch in surgical approaches to the orbit?
It marks the exit of the supraorbital nerve and artery
The supraorbital nerve and artery are critical structures that need to be considered during surgery to avoid complications.
What must be preserved during superior surgical approaches to the orbit?
The attachment of the trochlea for the superior oblique muscle
Preserving this attachment is important to maintain muscle function.
What distinguishes inferior approaches to the orbit from superior approaches?
Inferior approaches involve less important anatomic structures and encounter fewer blood vessels
This can result in a lower risk of complications during surgery.
What does computed tomography (CT) allow for in the evaluation of the orbital cavity?
Visualization of considerable detail of the orbital cavity and its contents
CT can reveal the walls of the orbital cavity, fascial planes, the eyeball, extraocular muscles, and large blood vessels.
What enhances the visualization of neoplasms and inflammatory tissue in CT scans?
Contrast enhancement by intravenous injection of an iodine-containing compound
This technique improves the clarity of the images and helps in diagnosing various conditions.
What is the most common imaging modality used when evaluating the bones of the orbit?
Computed tomography (CT)
CT is particularly useful following trauma to assess any potential injuries.
Fill in the blank: The _______ is an important landmark in superior approaches to the orbit.
supraorbital notch
What does Magnetic Resonance Imaging (MRI) provide better differentiation of?
Better differentiation between soft tissues
MRI is particularly useful for visualizing fine structures such as the optic nerve or muscles.
What is the primary use of ultrasonography in the context of the orbit?
Visualization of soft tissue
Ultrasonography employs high-frequency sound to achieve this visualization.
In A-scan ultrasonography, how are sound waves utilized?
Reflected at tissue interfaces and converted into an electric potential
This electric potential is displayed on a cathode ray oscillograph.
What structures can be visualized using A-scan ultrasonography?
- Optic nerve
- Eyeball
- Extraocular muscles
- Orbital fat
- Pathologic lesions
A-scan ultrasonography allows for detailed assessment of these structures.
What does B-scan ultrasonography provide?
A sectional representation of the eye
B-scan provides a more detailed view compared to A-scan.
Cover and label
1) lesser wing of sphenoid
2) orbital plate of frontal bone
3) zygomatic process of frontal bone
4) greater wing of sphenoid
5) orbital surface of zygomatic bone
6) inferior orbital fissure
7) zygomatic bone
8) infraorbital foramen
9) zygomatic bone
10) orbital surface of maxillary bone
11) orbital process of palatine bone
12) nasal bone
13) lacrimal bone
14) frontal process of maxilla
15) orbtial plate of ethmoid
16) sphenoid body
17) optic canal
18) superior orbital fissure
