Temporal Bone

Q: What parts make up the temporal bone?

It includes three elements: the petrous part (Pars petrosa), the tympanic part (Pars tympanica), and the squamous part (Pars squamosa).

Q: Which foramen lies between the styloid and mastoid processes?

The stylomastoid foramen (Foramen stylomastoideum) lies between these two processes on the inferior surface of the pyramid.

Os temporale

For medical students2 min readUpdated 2026-10-10

The temporal bone is a complex paired cranial bone that encloses the tympanic cavity. It consists of three main parts: the petrous, tympanic, and squamous parts, forming the housing for the structures of the middle ear and the auditory canals.

Bone typePaired cranial bone

PartsConsists of petrous, tympanic, and squamous parts

Key featureContains the tympanic cavity of the middle ear

Petrous Part (Pyramid)

The petrous part, or pyramid (Pars petrosa), is a massive pyramidal element of the bone. Its apex (Apex partis petrosae) is directed forward and medially, while its base faces posteriorly and laterally, smoothly transitioning into the prominent mastoid process (Processus mastoideus). This process is well-developed, deflected backward and laterally, and bounded by the occipital margin (Margo occipitalis).

The mastoid notch (Incisura mastoidea) is located on the mastoid process, along with the sulcus for the occipital artery (Sulcus arteriae occipitalis) and the sigmoid sulcus (Sulcus sinus sigmoidei). The sigmoid sulcus communicates with the external surface of the cranium through the mastoid foramen (Foramen mastoideum). A crucial feature of the petrous part is that it encloses the tympanic cavity (Cavitas tympani), which belongs to the middle ear.

Surfaces of the Pyramid

The pyramid has three distinct surfaces, each featuring complex landmarks:

The anterior surface bears the trigeminal impression (Impressio trigeminalis) and the arcuate eminence (Eminentia arcuata). Here also lies the tegmen tympani (Tegmen tympani) and the groove for the superior petrosal sinus.
The posterior surface features the internal acoustic opening (Porus acusticus internus), which leads into the internal acoustic meatus (Meatus acusticus internus). Nearby are the subarcuate fossa (Fossa subarcuata), the aperture of the vestibular canaliculus (Apertura canaliculi vestibuli) leading into the vestibular canaliculus (Canaliculus vestibuli), and the groove for the inferior petrosal sinus (Sulcus sinus petrosi inferioris).
The inferior surface includes the jugular notch (Incisura jugularis) with the intrajugular process (Processus intrajugularis) and the adjacent jugular fossa (Fossa jugularis). Here opens the aperture of the cochlear canaliculus (Apertura canaliculi cochleae), leading to the cochlear canaliculus. Anteriorly, the slender styloid process (Processus styloideus) projects downward. Between the styloid and mastoid processes lies the stylomastoid foramen (Foramen stylomastoideum). The external aperture of the carotid canal (Apertura externa canalis carotici) is also located on the inferior surface.

Tympanic Part

The tympanic part (Pars tympanica) forms the bony walls of the external acoustic meatus (Meatus acusticus externus). This canal begins with the external acoustic opening (Porus acusticus externus), which is circumferentially surrounded by the tympanic ring (Anulus tympanicus).

The ring features the major and minor tympanic spines (Spina tympanica major et minor). Along the border separating this part from the tympanic cavity runs the tympanic sulcus (Sulcus tympanicus), and the tympanic notch (Incisura tympanica) is located at its upper margin.

Squamous Part

The squamous part (Pars squamosa) consists of the temporal squama (Squama temporalis). It has two surfaces: the temporal surface (Facies temporalis) and the cerebral surface (Facies cerebralis), which are bounded by the sphenoidal and parietal margins (Margo sphenoidalis and Margo parietalis). The parietal notch (Incisura parietalis) separates the squama from the mastoid process. The groove for the middle temporal artery (Sulcus arteriae temporalis mediae) is visible on the temporal surface.

The zygomatic process (Processus zygomaticus) projects from the squama to participate in forming the zygomatic arch. In the region of this process are the supramastoid crest (Crista supramastoidea), the suprameatal pit (Foveola suprameatica), and the suprameatal spine (Spina suprameatica). Inferior to the process lies the mandibular fossa (Fossa mandibularis), bearing an articular surface (Facies articularis), anterior to which projects the articular tubercle (Tuberculum articulare).

Frequently asked questions

What structures pass through the internal acoustic meatus?

The facial and intermediate nerves pass through the internal acoustic meatus. At the fundus of the meatus begins the facial canal, where the facial nerve forms the geniculate ganglion; the intermediate nerve accompanies the facial nerve.

Which canals run within the petrous part of the temporal bone?

Seven canals (canals and canaliculi) run within the petrous part of the temporal bone:

Carotid canal (Canalis caroticus) — transmits the internal carotid artery.
Musculotubular canal (Canalis musculotubarius).
Facial canal (Canalis nervi facialis).
Caroticotympanic canaliculi (Canaliculi caroticotympanici).
Tympanic canaliculus (Canaliculus tympanicus).
Canaliculus for the chorda tympani (Canaliculus chordae tympani).
Mastoid canaliculus (Canaliculus mastoideus).

Other pathways (such as the vestibular and cochlear aqueducts) are not classified as canals.

Which nerve exits the cranial cavity through the stylomastoid foramen?

The facial nerve exits the cranial cavity through the stylomastoid foramen. This foramen is the termination of the facial canal, located on the inferior surface of the petrous part of the temporal bone.

Facial nerve (n. facialis) — exits the skull and gives off branches prior to entering the parotid gland: the posterior auricular nerve, and digastric and stylohyoid branches.

With which cranial bones does the temporal bone articulate?

The temporal bone articulates with the parietal bone via the squamous suture (sutura squamosa), with the occipital bone via the petro-occipital fissure (fissura petrooccipitalis), and with the mandible to form the temporomandibular joint. The zygomatic process of the temporal bone contributes to the zygomatic arch.

Which structures bound the mandibular fossa of the temporal bone?

The mandibular fossa is bounded by several bony landmarks of the temporal bone. Anteriorly and posteriorly, the boundaries are:

The base of the zygomatic process and articular tubercle (tuberculum articulare) — bound the fossa anteriorly.
The external acoustic opening — bounds the fossa posteriorly.

The fossa itself is divided approximately in half by the petrotympanic fissure into an anterior (intra-articular) and a posterior (extra-articular) part.

What parts make up the temporal bone?

It includes three elements: the petrous part (Pars petrosa), the tympanic part (Pars tympanica), and the squamous part (Pars squamosa).

Where is the tympanic cavity located?

The tympanic cavity of the middle ear is located inside the pyramid (petrous part) of the temporal bone.

Which foramen lies between the styloid and mastoid processes?

The stylomastoid foramen (Foramen stylomastoideum) lies between these two processes on the inferior surface of the pyramid.

Which structures form the external acoustic meatus?

Its bony walls are formed by the tympanic part of the temporal bone, and it begins with the external acoustic opening.

Go deeper

Detailed anatomy of the inner ear within the petrous pyramid
Walls and contents of the tympanic cavity (Cavitas tympani)
Complete course of the carotid canal and its internal apertures
Topography of cranial nerves in the internal acoustic meatus
Ligaments and joint capsule of the temporomandibular joint