Osteology of the skull

Question 1

Where does the olfactory nerve pass through?

Answer 1

Cribiform plate

Question 2

Name the attachment point for the falx cerebri.

Answer 2

Crista galli

Question 3

Name a cause of CSF rhinorrhea.

Answer 3

A punch to the nose can travel up to the crista galli and tear the dura. CSF can then flow through the cribiform foramina.

Question 4

Name the condition caused by a fracture to the orbital plate.

Answer 4

Periorbital ecchymosis (racoon eyes)

Question 5

Which cranial nerve passes through the foramen rotundum?

Answer 5

The maxillary branch of the trigeminal nerve (CN V2)

Question 6

Where do the pterygoid muscles travel through the skull?

Answer 6

Infratemporal fossa

Question 7

Which of the holes in the skull is covered with cartilage in life?

Answer 7

Foramen Lacerum

Question 8

The internal carotid artery runs over which structure to reach the cavernous sinus?

Answer 8

Foramen Lacerum

Question 9

Which cranial nerve passes through the foramen ovale?

Answer 9

Mandibular branch of the trigeminal nerve (V3)

Question 10

What structure passes through the foramen spinosum?

Answer 10

Middle meningeal artery

Question 11

What structure forms the boundary between the middle and posterior cranial floor?

Answer 11

Petrous part of the temporal bone

Question 12

What structure travels through foramen magnum?

Answer 12

The spinal cord

Question 13

Which structure does the vestibulocochlear nerve pass through?

Answer 13

Internal acoustic meatus

Question 14

Describe the intracranial path of the facial nerve.

Answer 14

The nerve arises in the pons, an area of the brainstem.

The roots travel through the internal acoustic meatus.

Still within the temporal bone, the roots leave the internal acoustic meatus, and enter into the facial canal. Within the facial canal, three important events occur:

Firstly the two roots fuse to form the facial nerve.
Next, the nerve forms the geniculate ganglion (a ganglion is a collection of nerve cell bodies).
Lastly, the nerve gives rise to:
Greater petrosal nerve – parasympathetic fibres to mucous glands and lacrimal gland.
Nerve to stapedius – motor fibres to stapedius muscle of the middle ear.
Chorda tympani – special sensory fibres to the anterior 2/3 tongue and parasympathetic fibres to the submandibular and sublingual glands.

The facial nerve then exits the facial canal (and the cranium) via the stylomastoid foramen. This is an exit located just posterior to the styloid process of the temporal bone.

Question 15

Which cranial nerves pass through the jugular foramen?

Answer 15

Glossopharangeal (CN IX), vagus (CN X) and accessory nerve (CN XI)

Question 16

Which structure transmits the hypoglossal nerve (CN XII)?

Answer 16

The hypoglossal canal

Question 17

A 28 year old cyclist is brought to the Emergency Department having fallen from his bike. He
appears confused, and is complaining of a slight headache. The doctor examining him cannot
see any obvious injuries to the patient’s head, but notices blood dripping from the external
auditory meatus (ear canal). There is also bruising on the bone behind the left ear.
A basilar skull fracture is suspected. On the basis of the clinical signs where within the base of
the skull is the fracture likely to be?

Answer 17

Petrous part of the temporal bone

Question 18

Name the dural venous sinuses found within the middle cranial fossa

Answer 18

Cavernous sinus

Question 19

Name the bones making up the Calverium (roof) of the skull

Answer 19

Frontal, Occipital and two parietal bones

Question 20

Name the bones making up the base of the skull

Answer 20

frontal, sphenoid, ethmoid, occipital, parietal and temporal bones.

Question 21

Name the facial bones

Answer 21

Zygomatic (2) – Forms the cheek bones of the face, and articulates with the frontal, sphenoid, temporal and maxilla bones.

Lacrimal (2) – The smallest bones of the face. They form part of the medial wall of the orbit.

Nasal (2) – Two slender bones, located at the bridge of the nose.

Inferior nasal conchae (2) – Located within the nasal cavity, these bones increase the surface area of the nasal cavity, thus increasing the amount of inspired air that can come into contact with the cavity walls.

Palatine (2) – Situated at the rear of oral cavity, and forms part of the hard palate.

Maxilla (2) – Comprises part of the upper jaw and hard palate.

Vomer – Forms the posterior aspect of the nasal septum.

Mandible (jaw bone) – Articulates with the base of the cranium at the temporomandibular joint (TMJ).

Question 22

The pterion is the junction between which bones?

Answer 22

Temporal, parietal, sphenoid and frontal

Question 23

Which bones form the anterior cranial fossa?

Answer 23

Frontal, ethmoid and sphenoid

Question 24

Which bones form the middle cranial fossa?

Answer 24

Sphenoid, temporal and parietal

Question 25

Which bones form the posterior cranial fossa?

Answer 25

Temporal and occipital

Question 26

Name the borders of the superior orbital fissure

Answer 26

Superior - Lesser wing of sphenoid bone

Inferior - Greater wing of sphenoid bone

Question 27

What structures are transmitted by the superior orbital fissure?

Answer 27

It transmits several structures that are listed below (from superior to inferior):

Lacrimal nerve
Frontal nerve – branch of ophthalmic nerve of trigeminal nerve (CN V)
Superior ophthalmic vein
Trochlear nerve (CN IV)
Superior division of the Oculomotor nerve (CN III)
Nasociliary nerve – branch of ophthalmic nerve of trigeminal nerve (CN V)
Inferior division of the Oculomotor nerve (CN III)
Abducens nerve (CN VI)
A branch of the Inferior ophthalmic vein