Petrous part of internal carotid artery

Anatomical features :
– Begins at the carotid foramen ( i.e. entry of carotid canal [1] in the petrous portion of the temporal bone [2] ) and leave at foramen lacerum

– Consists of three parts :
1. Vertical segment : Anterior to internal jugular vein [3]
2. Genu : Turns anteromedially in front of chochlea and tympanic cavity [4]
3. Horizontal segment : Travel towards cavernous sinus

Brief overview of various anatomical landmarks :
[1] Carotid canal
– Passage way in temporal bone through which the internal carotid artery enters the middle cranial fossa from the neck :
1. Starts from carotid foramen at inferior surface of temporal bone
2. Canal ascends vertically => bends forward and medialward
3. Ends at foramen lacerum at superior surface of skull base

[2] Petrous part of temporal bone ( relationship with ICA )
– Petrous means stone-like as it is one of the densest bone in the body
– Pyramidal shaped part of temporal bone contains the inner ear :
1. Petrous base : fuse with squamous and mastoid part of temporal bone
2. Petrous apex : point between posterior border of greater wing of sphenoid and basillar part of occipital bone
( i.e. Petrous apex forms the posteriolateral border of foramen lacerum )
[3] Internal jugular vein ( relationship with petrous part of ICA )
– Starts adjacent to petrous part of internal carotid artery as jugular foramen is just posterior to carotid foramen
– Internal jugular vein continues to travel vertically, while petrous part of ICA goes anteromedially to enter cranial fossa via foramen lacerum which is located near the cavernous sinus

[4] Typanic cavity ( relationship with ICA )
– Petrous part of ICA bends anteromedially in front of the tympanic cavity
( i.e. Petrous part of ICA is separated from tympanic cavity by a thin bony lamella only )