Using the Sectra table, you will identify the bones and meninges of the head. Bolded terms are in the objectives for this lab.
The skull
“All parts of the skull are fragile, but the bones of the orbit and nasal cavity are exceptionally delicate. Because the medial wall of the orbit is very easily broken, never hold a skull by placing your fingers your fingers into the orbits. Similarly, the small bony projections (processes) extending from the inferior surface of the skull can easily be broken by resting the skull on its base without the support of the mandible.” – Grant’s Dissector 16th ed.
Use the following view to identify the bones of the skull:
As you identify and dissect muscles, you should review their origin, insertion, innervation, and action(s). As you identify and dissect neurovascular structures, you should review their pathways.
If you are having trouble highlighting narrow structures (arteries, veins, nerves), you can search for them by selecting the Anatomy tab, typing the name of the structure in the search box, and selecting the sun icon next to the listed structure. You can dissect these structures by selecting the eye icon.
As you highlight a structure, note that the structure will also be highlighted in the multiplanar reconstructed (MPR), or cross-sectional images in the leftmost pane. All structures should be identified on the MPR images. Using three fingers, scroll through the MPR images to understand the three-dimensional relationships between different structures as you work though the lab. Structures that are difficult to identify in the MPR images will have additional links to assist you.
Identify the bones of the skull (bony features can’t be identified on the model):
- Identify the frontal, nasal, maxillary, lacrimal, ethmoid, sphenoid, temporal, zygomatic, parietal, and occipital bones
- Identify the mandible
- Sutures are the fibrous joints between bones of the skull. Identify the following sutures (they cannot be highlighted on the model): coronal suture, sagittal suture, lambdoid suture, and squamosal suture
- Use the diagrams below to identify the following landmarks of the skull: glabella, bregma, nasion, pterion, lambda, and vertex
Q1: What bones contribute to the anterior cranial fossa? The middle cranial fossa? The posterior cranial fossa? (answer)
The meninges
The meninges are not visible on the model. Identify the following structures in the diagrams below:
- Dura mater: epidural space, falx cerebri, tentorium cerebelli, diaphragma sellae, and tentorial notch
- Arachnoid mater: cerebral veins and subarachnoid space
- Pia mater
Q2: Where are epidural hematomas located? Subdural hematomas? (answer)
Blood flow in the cranium
- Dissect the frontal and parietal bones
- Identify the dural venous sinuses: superior sagittal sinus, inferior sagittal sinus, straight sinus, confluence of sinuses, transverse sinuses, and sigmoid sinuses (MPR)
- The cavernous sinus is not visible on the model, identify it on the diagrams below
- Identify the internal carotid arteries (MPR)
Q3: Trace blood flow from the inferior sagittal sinus to the internal jugular vein. What foramen will it pass through? (answer)
Cranial nerves
- Identify the 12 cranial nerves: CN I – XII
- The middle meningeal arteries are not visible in the intercranial space on the model. Identify them on the diagrams below
Q4: What foramina/spaces do each cranial nerve pass through to exit the intercranial space? (answer)
End of Sectra activity
Answers to activity questions
Below are answers to questions asked during the activity. Clicking the ‘back to lab’ link below each answer will take you back to the question (you may need to scroll up a little to view the question again).
Q1: What bones contribute to the anterior cranial fossa? The middle cranial fossa? The posterior cranial fossa?
- Anterior cranial fossa: frontal bone, ethmoid bone, sphenoid bone
- Middle cranial fossa: sphenoid bone, temporal bones, parietal bones
- Posterior cranial fossa: occipital bone, temporal bones, parietal bones
Q2: Where are epidural hematomas located? Subdural hematomas?
- Epidural hematomas: located between the dura mater and the skull due to a tear in a meningeal artery
- Subdural hematomas: located between the dura mater and arachnoid mater due to a tear in the bridging or cerebral veins
Q3: Trace blood flow from the inferior sagittal sinus to the internal jugular vein. What foramen will it pass through?
- Inferior sagittal sinus –> straight sinus –> confluence of sinuses –> transverse sinus –> sigmoid sinus –> jugular foramen –> internal jugular vein
Q4: What foramina/spaces do each cranial nerve pass through to exit the intracranial space?
- Olfactory nerve (CN I): the cribriform plate (olfactory nerves originate at the olfactory bulb and pass through the cribriform plate to enter the olfactory epithelium)
- Optic nerve (CN II): the optic canal (to the orbit)
- Oculomotor nerve (CN III): the superior orbital fissure (to the orbit)
- Trochlear nerve (CN IV): the superior orbital fissure (to the orbit)
- Trigeminal nerve (CN V)
- Ophthalmic nerve (CN V1): superior orbital fissure (to the orbit)
- Maxillary nerve (CN V2): foramen rotundum (to pterygopalatine fossa)
- Mandibular nerve (CN V3): foramen ovale (to infratemporal fossa)
- Abducens nerve (CN VI): superior orbital fissure (to the orbit)
- Facial nerve (CN VII): internal acoustic meatus
- The greater petrosal nerve goes to the pterygoid canal
- The chorda tympani travels to the infratemporal fossa
- Efferent motor fibers (the facial nerve) exit the stylomastoid foramen
- Vestibulocochlear nerve (CN VIII): internal acoustic meatus
- Glossopharyngeal nerve (CN IX): jugular foramen
- Vagus nerve (CN X): jugular foramen
- Accessory nerve (CN XI): enters the intracranial space through the foramen magnum, then exits through the jugular foramen
- Hypoglossal nerve (CN XII): hypoglossal canal