Description
A canal within the petrous part of the temporal bone between the posterior cranial fossa and inner ear. It provides a passage
Shape, size, location
Variable length but approximately 1cm long with smooth rounded outer margins. Located within the posterior cranial fossa, in the centre of the posterior surface of the petrous part of the temporal bone.
The canal narrows as it moves towards the fundus.
Structure
Fundus
- A thin cribriform plate of bone which forms the lateral aspect of the canal
- Separates the IAM from the cochlear and vestibule
- Subdivided by two thin crests of bone to form three separate osseous canals
- Transmits the facial and vestibulocochlear nerve branches
Contents
- Facial nerve
- Lies superiorly within the canal
- nervus intermedius (sensory/parasympathethic)
- facial motor root (motor)
- Upon reaching the facial canal, the nervus intermedius and motor root of the facial nerve join to form the geniculate ganglion
- Vestibulocochlear nerve
- Lies inferiorly within the canal
- inferior vestibular nerve (posterior within canal)
- superior vestibular nerve (posterior within canal)
- cochlear nerve (anterior within canal)
- Vestibular ganglion
- Labyrinthine artery (usually a branch of the AICA or basilar artery)
What other structures pass through the internal auditory canal? (3)
d) What structures form the horizontal and vertical divisions of the lateral portion of the internal auditory canal? (2)
e) Describe the position of the structures in the lateral portion of the internal auditory canal? (4)