Cranial Fossa Contents Quiz
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Questions and Answers

The trigeminal nerve exits the pons via two roots, with the motor root emerging somewhat below and medial to the sensory root.

False (B)

Within Meckel's cave, the ophthalmic fibers of the trigeminal nerve lie most laterally.

False (B)

The abducent nerve exits the brainstem near the ventral midline at the junction of the pons and the pyramid of the medulla and then runs downwards through the pontine cistern.

False (B)

The relatively short intracranial course of the abducent nerve renders it particularly vulnerable to increases in intracranial pressure.

<p>False (B)</p> Signup and view all the answers

The labyrinthine artery, which runs with the facial and vestibulocochlear nerves, typically branches off the basilar artery and rarely originates from the anterior inferior cerebellar artery.

<p>False (B)</p> Signup and view all the answers

The internal acoustic meatus is a foramen directed laterally in the anterior surface of the obliquely set petrous bone.

<p>False (B)</p> Signup and view all the answers

At the junction with the pons the mandibular fibres lie superior, the ophthalmic fibers inferior with the maxillary fibres between.

<p>True (A)</p> Signup and view all the answers

The foramen singulare transmits the nerve to the anterior semicircular duct.

<p>False (B)</p> Signup and view all the answers

The inner layer of the dura mater is everywhere separated from the endosteum within the internal acoustic meatus.

<p>False (B)</p> Signup and view all the answers

The subarcuate fossa, located lateral to the internal acoustic meatus, becomes proportionally larger in the neonatal skull compared to the adult skull.

<p>True (A)</p> Signup and view all the answers

The endolymphatic sac is suspended from a narrow slit overhung by a sharp bone scale at the orifice of the cochlear aqueduct.

<p>False (B)</p> Signup and view all the answers

Within the internal acoustic meatus, the facial nerve pierces the back of the upper part of the lamina cribrosa.

<p>False (B)</p> Signup and view all the answers

The glossopharyngeal, vagus, and accessory nerves emerge from the medulla oblongata in a vertical series of rootlets located between the olive and the superior cerebellar peduncle.

<p>False (B)</p> Signup and view all the answers

Each division of the vestibular nerve has a ganglion deep in the meatus.

<p>True (A)</p> Signup and view all the answers

Within the jugular foramen, the glossopharyngeal nerve and the inferior petrosal sinus are located in the middle compartment.

<p>False (B)</p> Signup and view all the answers

The cochlear canaliculus is indented by the hypoglossal nerve.

<p>False (B)</p> Signup and view all the answers

The spinal root of the accessory nerve enters the posterior fossa through the foramen ovale.

<p>False (B)</p> Signup and view all the answers

The hypoglossal nerve exits the medulla oblongata via rootlets positioned between the pyramid and the gracile tubercle.

<p>False (B)</p> Signup and view all the answers

The vertebral artery pierces the spinal dura mater and arachnoid, then runs behind the denticulate ligament.

<p>False (B)</p> Signup and view all the answers

The basilar artery is typically positioned precisely within the ventral median groove of the pons.

<p>False (B)</p> Signup and view all the answers

Flashcards

Posterior Cranial Fossa

The cavity in the skull that houses the cerebellum, pons, and medulla oblongata.

Cerebellar Hemispheres

The two halves of the cerebellum located in the posterior cranial fossa.

Cranial Nerves V to XII

Nerves that pierce the dura mater in the posterior cranial fossa, controlling various functions.

Trigeminal Nerve

Cranial nerve V; has a sensory root and a motor root that control facial sensations and chewing.

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Mandibular Fibres

Part of the trigeminal nerve that carries sensory and motor information from the jaw.

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Abducent Nerve

Cranial nerve VI; controls lateral eye movement and is vulnerable to pressure changes.

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Internal Acoustic Meatus

A canal in the petrous bone for cranial nerves VII and VIII and the labyrinthine artery.

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Labyrinthine Artery

An artery typically branching from the basilar artery, travels with facial and vestibulocochlear nerves.

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Facial Nerve

Cranial nerve VII; controls facial expressions and parts of taste.

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Vestibular Nerve

Part of cranial nerve VIII; involved in balance and spatial orientation.

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Foramen Singulare

A passage for the nerve to the posterior semicircular duct, located in the internal acoustic meatus.

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Jugular Foramen

An opening in the skull where several cranial nerves and veins pass.

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Accessory Nerve

A cranial nerve that supplies muscles of the neck and shoulders.

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Cochlear Canaliculus

A small canal that allows the glossopharyngeal nerve to enter the cochlea.

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Aqueduct of the Vestibule

A passage in the ear that connects the inner ear structures.

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Vertebral Arteries

Arteries that supply blood to the brain and spinal cord, running alongside the vertebrae.

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Basilar Artery

An artery formed by the joining of vertebral arteries, supplying the brainstem and cerebellum.

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Hypoglossal Nerve

Cranial nerve responsible for tongue movements.

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Posterior Fossa

A depression in the skull base housing the cerebellum and brainstem.

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Study Notes

Posterior Cranial Fossa Contents

  • Houses cerebellar hemispheres, pons, and medulla oblongata

  • Cranial nerves V-XII pass through the dura mater

  • Trigeminal nerve:

    • Two roots (large sensory, small motor) near each other
    • Motor root emerges above/medial to sensory, then spirals to Meckel's cave
    • Sensory root fibers spiral
    • Mandibular fibers superior, ophthalmic inferior in pons, swapped in Meckel's cave

  • Abducent nerve:

    • Leaves brainstem at pons-medulla junction, travels upwards through pontine cistern
    • Evaginates dura mater, runs between dura layers to inferior petrosal sinus, entering cavernous sinus

  • Facial and vestibulocochlear nerves (with nervus intermedius):

    • Depart pons-medulla junction, pass laterally/upward, entering internal acoustic meatus
    • Labyrinthine artery accompanies them

Internal Acoustic Meatus

  • Foramen on petrous bone's posterior surface
  • Fundus (base) is lamina cribrosa, divided by horizontal crest into upper/lower semicircle.
  • Dura mater fused with endosteum inside meatus
  • Structures within meatus:
    • Cochlea in front of vestibule
    • Facial nerve above, cochlear nerve (many branches in spiral) in lower part
    • Vestibular nerve behind facial nerve; upper and lower divisions with ganglia, and a single foramen (foramen singulare) for the posterior semicircular duct
    • Labyrinthine artery and its branches accompanying nerves

Subarcuate Fossa

  • Lateral to internal acoustic meatus, below arcuate eminence
  • Shallow fossa for flocculus of cerebellum
  • In newborns, as wide and deep as internal acoustic meatus

Aqueduct of the Vestibule

  • Narrow slit on petrous bone's posterior surface, overlaying endolymphatic sac
  • Endolymphatic sac hangs beneath dura matter

Glossopharyngeal, Vagus, and Accessory Nerves

  • Arise from medulla oblongata, in order listed from olive to inferior cerebellar peduncle
  • Pass laterally, across occipital bone, behind jugular tubercle
  • Pass through jugular foramen
  • Spinal root of accessory nerve enters posterior fossa through foramen magnum
  • Originates from upper cervical segments, lateral to denticulate ligament
  • Joins cranial root medial to jugular foramen

Jugular Foramen

  • Divided by dura mater septa into 3 compartments

  • Glossopharyngeal nerve and inferior petrosal sinus in anterior

  • Vagus and accessory nerves in middle

  • Sigmoid sinus in posterior

  • Cochlear canaliculus:

  • Deep notch below internal acoustic meatus

  • Glossopharyngeal nerve indents it

  • Aqueduct of the cochlea within canaliculus, perilymph drains here to subarachnoid space

Hypoglossal Nerve

  • Medulla, emerges as rootlets between pyramid and olive
  • Two roots enter hypoglossal canal, separated by dura mater septum
  • Canal lies in epiphyseal junction of basiocciput and jugular process of occipital bone

Posterior Fossa Arteries

  • Vertebral and Basilar arteries with branches
  • Vertebral arteries give off meningeal branches before entering posterior fossa
  • Branches pass between dura layers, at foramen magnum
  • Vertebral artery gives rise to posterior spinal arteries
  • Then runs forward, in front of denticulate ligament
  • Gives anterior spinal artery and posterior inferior cerebellar artery, spirals to join opposite artery to form basilar artery
  • Posterior and anterior spinal arteries pass downwards through foramen magnum
  • Posterior inferior cerebellar artery is highly convoluted, passing between rootlets of hypoglossal, accessory, and vagus nerves. Distributed to cerebellum and medulla
  • Basilar artery runs in front of pons
  • Gives anterior inferior cerebellar, pontine branches before branching to posterior cerebral arteries at pons' upper border
  • Labyrinthine artery arises from anterior inferior cerebellar artery or basilar trunk.

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Description

Test your knowledge of the posterior cranial fossa and its contents, including the cranial nerves and their pathways. This quiz covers the structures of the cranial cavity and the internal acoustic meatus, providing a thorough review of key concepts in neuroanatomy.

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