The cranial cavity and face week 1 Flashcards
(37 cards)
Identify the features of the roof of the cranial cavity.
What is the name of this part of the cranium?
anterior cranial fossa
Identify the bones/foramina/prominences associated with the anterior cranial fossa.
What portion of the anterior cranial fossa does the frontal bone form? What does the frontal bone do for the orbit?
What portion of the anterior cranial fossa does the ethmoid bone form?
What is the function of the crista galli? What bone is it a part of?
What is the function of the foramen cecum?
What is the purpose of the foramina in the cribiform plate? What bone is the cribiform plate a part of?
What is the function of the anterior clinoid process?
Bones Associated with the Anterior Cranial Fossa:
- Frontal bone- is found anteriorly and forms the floor of the anterior cranial fossa and a roof over the orbit
- Ethmoid bone- is located centrally in the anterior cranial fossa forming part of the floor
- Sphenoid Bone- specifically the body and lesser wing of the sphenoid bone, are found posteriorly in the anterior cranial fossa
Foramina/Bony Prominences Associated with the Anterior Cranial Fossa:
- Crista Galli- part of the ethmoid bone which is the point of attachment for the falx cerebri (defined later in this lecture)
- Cribiform Plate of Ethmoid Bone- Contains foramina for passage of the olfactory nerves from the nasal cavities to the olfactory bulb of the brain
- Foramen Cecum- found between the frontal and ethmoid bones, this foramen allows passage of emissary veins which connect the nasal cavity with the superior sagittal sinus
- Anterior Clinoid Process- Part of lesser wing of sphenoid bone and site of attachment of tentorium cerebelli (defined later in this lecture)
Identify the bones/foramina/bony prominences of the middle cranial fossa.
What parts of the middle cranial fossa does the sphenoid bone contribute to?
What parts of the temporal bone contribute to the middle cranial fossa?
What part of the middle cranial fossa does the parietal bone contribute to?
Bones Associated with the Middle Cranial Fossa:
- Sphenoid Bone- Specifically the body and greater wings of the sphenoid bone contribute to the floor and lateral aspects of this fossa
- Temporal bone- Specifically the squamous part laterally and the petrous part posteriorly.
- Parietal Bone- Contributes to the lateral boundaries
What bone is the optic canal formed in? What is the purpose of the optic canal?
Where is the superior orbital fissure located? What does it transmit?
What does the foramen rotundum transmit?
What does the foramen ovale transmit?
What does the foramen spinosum transmit?
What organ is located in the hypophysial fossa?
Foramina/Bony Prominences Associated with the Middle Cranial Fossa:
- Optic canal: in the sphenoid bone allows passage of the optic nerve (CN II) from the orbit to the brain. Also transmits the opthalmic artery. This foramen may be considered part of the anterior or middle cranial fossa.
- Superior Orbital Fissure- is found between the greater and lesser wings of the sphenoid bone and transmits ophthalmic veins and nerves (CN III, CN IV, CN V1, CN VI, and sympathetic fibers entering the orbit).
- Foramen Rotundum- transmits V2 (maxillary nerve) to supply the skin, teeth, and mucosa related to the maxilla (upper jaw)
- Foramen Ovale- opens inferiorly to the infratemporal fossa and transmits CN V3 (mandibular nerve) and accessory meningeal artery
- Foramen Spinosum- also connects with the infratemporal fossa and transmits the middle meningeal artery (the groove for which can clearly be seen on the floor and lateral wall of the middle cranial fossa.
- Hypophysial Fossa: Note that this fossa houses the pituitary gland. You will learn later that the pituitary gland is surrounded by the Circle of Willis, a critical component of the vascular supply to the brain.
Identify the bones/foramina/bony prominences of the posterior cranial fossa.
What portion of the posterior cranial fossa does the occipital bone contribute to?
What is the contribution of the sphenoid bone to the posterior cranial fossa?
What parts of the temporal bone are in the posterior cranial fossa?
Bones Associated with the Posterior Cranial Fossa:
- Occipital bone- forms most of the posterior cranial cavity
- Sphenoid Bone- the dorsum sellae marks the anterior most aspect of this fossa
- Temporal Bone- the petrous and mastoid parts of the temporal bone contribute to the anterior-lateral walls of the fossa
- Parietal Bone
What is the internal occipital protuberance and grooves for transverse and sigmoid sinuses formed by?
What structures pass through the jugular foramen?
What does the internal acoustic meatus transmit?
What goes through the hypoglossal canal?
What lies against the clivus?
Foramina/Bony Prominences Associated with the Posterior Cranial Fossa:
- Internal occipital protuberance- is formed in relation to the confluence of sinuses (defined later in this lecture)
- Grooves for the transverse and sigmoid sinuses- are also created by the dural (cranial) sinuses (defined later in this lecture)
- Jugular foramen- transmits CN IX, X, and XI as well as the sigmoid sinus as it exits the skull as the internal jugular vein
- Internal acoustic meatus- transmits CN VII and VIII as well as the labyrinthine artery
- Hypoglossal canal- transmits the hypoglossal nerve (CN XII)
- The clivus: the brainstem, specifically the pons, lies against the clivus and extends from this region of bone to the foramen magnum, the large opening at the base of the skull. It is possible for the brainstem to “slide downward” along the clivus herniating into the foramen magnum. This typically would result from a pressure difference between the cranial and spinal cavities.
What is the difference between cranial dura and spinal dura?
Cranial dura mater is continuous with spinal dura mater, though the cranium the dura mater exists in 2 layers.
What 2 types of structures are created by separation of cranial dura mater?
The cranial dura mater exists in two layers which are fused together as the dura lines the cranial cavity. There are locations within the cranial cavity where the two layer of dura separate creating two types of structures:
1) Dural partitions: which incompletely separate parts of the brain
2) Dural venous sinuses (a.k.a. intracranial venous structures)
Where is the falx cerebri located? What does it do? What is the falx cerebri attahced to?
Where is the tentorium cerebelli located? What does it do? What is the tentorium cerebelli attached to?
Where is the falx cerebelli located? What does it do? What is the falx cerebelli attached to?
What does the diaphragma sellae do?
- Falx cerebri: is a crescent shaped structure that projects downward between the two cerebral hemispheres. It is attached anteriorly to the crista galli and the frontal crest (of the frontal bone) and blends posteriorly with the tentorium cerebelli. The falx is visible on CT imaging and should lie in the midline between the two cerebral hemispheres. Pathological processes inside the cranial cavity (e.g. a tumor or a bleed) may cause a deviation of the falx to one side.
- Tentorium cerebelli: is a horizontal projection of dura that covers the posterior cranial fossa. It attaches posteriorly to the occipital bone along the groove for the transverse sinuses, laterally to the petrous part of the temporal bone and anteriorly to the clinoid processes. This piece of dura separates the cerebellum (below) from the cerebrum (above).
- Falx cerebelli: is a small midline projection of dura within the posterior cranial fossa. It is attached superiorly to the tentorium cerebelli and posteriorly to the occipital bone. It separates the two halves of the cerebellum.
- Diaphragma Sellae: is a small horizontal shelf of dura that covers over the hypophysial fossa, which houses the pituitary gland.
meningiomas
Meningiomas are benign intracranial tumors which may arise from any part of the meninges and impact the surrounding brain tissue.
Where is the cerebrum located with respect to the tentorium cerebelli?
The corpus callosum (connects hemispheres of the brain) is situated where in relation to the falx cerebri?
What fossa does the frontal lobe of the brain lie in? What fossa does the temporal lobe lie in?
o The cerebrum (cerebral cortex & underlying structures) is situated above the tentorium cerebelli.
o The cerebrum is partitioned into right and left hemispheres by the falx cerebri in the midsagittal plane.
o The corpus callosum connecting the two hemispheres passes just beneath the falx cerebri.
o The frontal lobe of the brain lies in the anterior cranial fossa and the temporal lobes fill the middle fossa.
Where is the posterior fossa located in relation to the tentorium cerebelli?
What 3 structures does the posterior fossa contain?
The posterior fossa lies below the tentorium cerebelli and includes
1) the brainstem from which cranial nerves III thru XII originate and pass anteriorly to enter the various foramina of the skull;
2) the cerebellum which is attached by major fiber bundles (peduncles) to the dorsal aspect of the brainstem;
3) the vertebral-basilar arterial supply (See Gross Topography 2 Lecture) to the brainstem and cerebellum.
How is the brainstem connected to the cerebrum? What do interruption of pathways in this region lead to?
The brainstem is connected to the cerebrum through the tentorial notch. This is a critical area for compression resulting from herniation, trauma, or mass lesions. Interruption of pathways in this narrow region commonly results in conditions in which the cerebral cortex is essentially disconnected from the brainstem and cord.
What vessels does the dura mater receive its blood supply from?
What is the name of the largest and most significant of these vessesl? How does this vessel enter the cranial cavity?
What can rupture of this vessel lead to?
The dura receives blood supply from the meningeal arteries. The largest and most significant of these vessels is the middle meningeal artery. This vessel enters the cranial cavity via the foramen spinosum and cuts a groove in the bone on the floor and lateral wall of the middle cranial fossa. (Look for this in you skulls and in atlas pictures!) This vessel can rupture in trauma to the head (e.g. fractures of temporal bone). When it ruptures, bleeding occurs between the two layers of dura and between the periosteal layer of dura and the skull. These bleeds are epidural hemorrhages. This is a life threatening condition as the hemorrhage and associated swelling may compress brain tissue and vasculature to the brain.
From what nerve does the dura mater receive innervation? What kind of innervation is it? (GSA, GVE, etc.)
The dura mater receives sensory innervation (GSA fibers) from all three divisions of the Trigeminal nerve (CN V).
Venous drainage of the brain ultimately empties into the ____ ____ ____.
dural venous sinuses
Between what menigeal layer(s) are dural venous sinuses located?
What do dural venous sinuses ultimately drain into?
What 2 types of veins drain into dural venous sinuses? Where do these veins drain blood from?
- Venous drainage of the brain ultimately empties into the dural venous sinuses.
- The dural sinuses are endothelial-lined spaces between the outer periosteal and inner meningeal layers of dura.
- This network of dural sinuses will drain into the internal jugular veins.
- Also draining into these sinuses are:
- Diploic veins: draining blood from the skull
- Emissary Veins: draining blood from outside the cranial cavity.
Why are emissary veins clincally important?
Emissary veins are clinically important because they are a conduit by which infections can enter the cranial cavity from outside because they have no valves.
Identify the indicated veins.
What sinuses drain into the confluence of sinuses?
What sinuses drain blood from the confluence of sinuses?
The superior sagittal and straight sinuses as well as the occipital sinus (in the falx cerebelli) drain into the confluence of sinuses.
The paired transverse sinuses drain blood from the confluence of sinuses.
