Petrous portion of the internal carotid artery
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Petrous portion of the internal carotid artery
Internal carotid artery
In human anatomy, the internal carotid arteries are two major arteries, one on each side of the head and neck. They arise from the common carotid arteries where these bifurcate into the internal and external carotid artery, and they supply the brain....

(or petrous segment).—When the internal carotid artery enters the canal in the petrous portion
Petrous portion
Petrous portion can refer to:* Petrous portion of the temporal bone* Petrous portion of the internal carotid artery...

 of the temporal bone
Temporal bone
The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebrum.The temporal bone supports that part of the face known as the temple.-Parts:The temporal bone consists of four parts:* Squama temporalis...

, it first ascends a short distance, then curves forward and medially, and again ascends as it leaves the canal to enter the cavity of the skull between the lingula
Lingula
Lingula is Latin for "little tongue". It can stand for:* Lingula , a brachiopod genus of the family Lingulidae, which is among the few brachiopods surviving today but also known from fossils over 500 million years old* In anatomy:...

 and petrosal process
Petrosal process
On either side of the dorsum sellae of the sphenoid bone is a notch for the passage of the abducent nerve, and below the notch a sharp process, the petrosal process, which articulates with the apex of the petrous portion of the temporal bone, and forms the medial boundary of the foramen lacerum....

 of the sphenoid
Sphenoid bone
The sphenoid bone is an unpaired bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone.The sphenoid bone is one of the seven bones that articulate to form the orbit...

.

The artery lies at first in front of the cochlea
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....

 and tympanic cavity
Tympanic cavity
The tympanic cavity is a small cavity surrounding the bones of the middle ear.It is formed from the tubotympanic recess, an expansion of the first pharyngeal pouch....

; from the latter cavity it is separated by a thin, bony lamella, which is cribriform
Cribriform
Cribriform can refer to:* Cribriform plate* Fascia cribrosa* Cribriform mesenchyme...

 in the young subject, and often partly absorbed in old age
Old age
Old age consists of ages nearing or surpassing the average life span of human beings, and thus the end of the human life cycle...

.

Farther forward it is separated from the semilunar ganglion by a thin plate of bone, which forms the floor of the fossa for the ganglion
Ganglion
In anatomy, a ganglion is a biological tissue mass, most commonly a mass of nerve cell bodies. Cells found in a ganglion are called ganglion cells, though this term is also sometimes used to refer specifically to retinal ganglion cells....

 and the roof of the horizontal portion of the canal.

Frequently this bony plate is more or less deficient, and then the ganglion is separated from the artery by fibrous membrane.

The artery is separated from the bony wall of the carotid canal
Carotid canal
On the interior surface of the temporal bone, behind the rough surface of the apex, is the large circular aperture of the carotid canal, which ascends at first vertically, and then, making a bend, runs horizontally forward and medialward.-Contents:...

 by a prolongation of dura mater
Dura mater
The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...

, and is surrounded by a number of small veins and by filaments of the carotid plexus
Carotid plexus
Carotid plexus can refer to:* Common carotid plexus* Internal carotid plexus* External carotid plexus...

, derived from the ascending branch of the superior cervical ganglion
Superior cervical ganglion
The superior cervical ganglion , the largest of the cervical ganglia, is placed opposite the second and third cervical vertebræ. It contains neurons that supply sympathetic innervation to the face....

 of the sympathetic trunk
Sympathetic trunk
The sympathetic trunks are a paired bundle of nerve fibers that run from the base of the skull to the coccyx.-Structure:...

.
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