Foramina of the anterior and middle cranial fossae
The anatomical structures of the anterior and middle cranial zones serve as pathways for the nerves responsible for olfaction and facial innervation, as well as for the vessels supplying the meninges.
- Foramen caecum (foramen caecum): transmits a specific emissary vein that provides venous outflow.
- Cribriform foramina (foramina cribrosa): serve as the passage for olfactory nerve filaments (responsible for the perception of smell) and meningeal branches.
- Foramen rotundum (foramen rotundum): contains exclusively neural structures, specifically the maxillary nerve.
- Foramen ovale (foramen ovale): through it, the mandibular nerve leaves the cranial cavity, and an accessory branch of the middle meningeal artery also passes.
- Foramen spinosum (foramen spinosum): serves as the main pathway for the middle meningeal artery, its accompanying veins, and also transmits a small branch of the mandibular nerve.
- Foramen lacerum (foramen lacerum): transmits the greater and lesser petrosal nerves, as well as the glossopharyngeal nerve (CN IX).
Foramina and canals of the posterior cranial fossa and temporal bone
The posterior cranial fossa and temporal bone structures contain the largest and most functionally significant foramina, through which pass the brainstem, organs of hearing and balance, and the caudal group of cranial nerves.
- Jugular foramen (foramen jugulare): a massive conduit through which three pairs of cranial nerves (CN IX, X, and XI) pass simultaneously, along with veins.
- Internal acoustic meatus (meatus acusticus internus): contains the facial (VII) and vestibulocochlear (VIII) nerves, as well as labyrinthine arteries and veins supplying the inner ear.
- Foramen magnum (foramen magnum): the largest foramen of the skull. It houses the medulla oblongata and transmits accompanying arteries and nerves.
- Hypoglossal canal (canalis hypoglossi): an isolated pathway for the hypoglossal nerve (CN XII).
Additionally, within the temporal bone structures, there are canaliculi associated with the inner ear:
- Cochlear canaliculus (canaliculus cochleae) and vestibular canaliculus (canaliculus vestibuli): contain the perilymphatic and endolymphatic ducts, respectively.
Other canals and foramina
In addition to major pathways, the cranial bones contain a series of specialized canals and foramina that perform localized functions.
- Canals of the pterygopalatine ganglion: the palatovaginal (canalis palatovaginalis) and vomerovaginal (canalis vomerovaginalis) canals contain vessels and nerves related to the pterygopalatine ganglion.
- Mandibular canal (canalis mandibulae): runs within the thickness of the bone and serves as a passage for the inferior alveolar nerve and corresponding blood vessels.
- System of emissary veins: in addition to the foramen caecum, emissary veins are located in the mastoid (foramen mastoideum), parietal (foramen parietale), and condylar (foramen condylaris) foramina.
Briefly: answers to topical questions
What passes through the foramen lacerum?
The foramen lacerum transmits the greater and lesser petrosal nerves, the glossopharyngeal nerve (CN IX), and emissary veins connecting the pterygoid plexus with the cavernous sinus. In a living person, the area of the foramen is occupied by a permanent synchondrosis.
What structures pass through the jugular foramen?
The jugular foramen transmits cranial nerves and venous structures responsible for innervation and venous drainage. The contents of the foramen include:
- Glossopharyngeal nerve (CN IX) — a cranial nerve.
- Vagus nerve (CN X) — a cranial nerve.
- Accessory nerve (CN XI) — a cranial nerve.
- Sigmoid sinus (sinus sigmoideus) — passes through the foramen and continues as the superior bulb of the internal jugular vein.
What anatomical structures pass through the foramen magnum?
The foramen magnum transmits the medulla oblongata, arteries, and nerves; the vertebral arteries enter the cranial cavity through it.
What passes through the superior orbital fissure?
The superior orbital fissure transmits cranial nerves and blood vessels. The contents of the fissure include:
- Oculomotor nerve (n. oculomotorius, CN III) — innervates the extraocular muscles.
- Trochlear nerve (n. trochlearis, CN IV) — innervates the superior oblique muscle.
- Abducens nerve (n. abducens, CN VI) — innervates the lateral rectus muscle.
- Ophthalmic nerve (n. ophthalmicus) — the first branch of CN V.
- Superior ophthalmic vein (v. ophthalmica superior) — enters the cranial cavity.
- Anterior meningeal branches (r. meningeus anterior) — from the ophthalmic artery (present occasionally).
What structures exit through the stylomastoid foramen?
Important neural and venous structures that are closely related anatomically exit through the stylomastoid foramen to the external skull base. These include:
- Facial nerve (n. facialis) — emerges from the canal of the same name.
- Stylomastoid vein (v. stylomastoidea) — accompanies the facial nerve as it exits the foramen.
What passes through the foramen ovale?
The foramen ovale transmits neural, arterial, and venous structures connecting the cranial cavity with the external skull base. The contents of the foramen include:
- Mandibular nerve (n. mandibularis) — the third branch of CN V.
- Accessory branch of the middle meningeal artery — a blood vessel.
- Venous plexuses of the foramen ovale — connect the pterygoid plexus with the cavernous sinus.
Where are the emissary veins of the skull located?
Emissary veins are located in various foramina and canals of the cranial bones, ensuring venous drainage. They are found in the following anatomical structures:
- Foramen caecum (foramen caecum) — emissary vein.
- Mastoid foramen (foramen mastoideum) — mastoid emissary vein.
- Parietal foramen (foramen parietale) — parietal emissary vein.
- Condylar canal (canalis condylaris) — venous emissary.
- Foramen lacerum (foramen lacerum) — emissary veins of the foramen lacerum.
What passes through the optic canal?
The optic canal transmits structures of the visual system and blood vessels heading toward the orbit. The contents of the canal include:
- Optic nerve (n. opticus, cranial nerve II) — a special sensory nerve.
- Ophthalmic artery (a. ophthalmica) — a branch of the internal carotid artery.
- Central retinal artery (a. centralis retinae) — a branch of the ophthalmic artery.
Which nerves and vessels are contained within the mandibular canal?
The mandibular canal transmits the inferior alveolar nerve and vessels.
To memorize the contents of the foramen rotundum and foramen ovale, use the mnemonic: «Rotundum = Maxillary, Ovale = Mandibular nerve».
Class and exam questions
Which nerves pass through the jugular foramen?
The jugular foramen (foramen jugulare) transmits the IX, X, and XI cranial nerves, as well as corresponding veins.
What is located in the foramen magnum?
The foramen magnum transmits the medulla oblongata, along with a number of arteries and nerves connecting the cranial cavity to the vertebral canal.
Through which foramen does the middle meningeal artery pass?
The main trunk of the middle meningeal artery, along with its accompanying vein and a branch of the mandibular nerve, passes through the foramen spinosum.
Where do the perilymphatic and endolymphatic ducts run?
These inner ear structures pass through the cochlear canaliculus (canaliculus cochleae) and the vestibular canaliculus (canaliculus vestibuli).
What else to study on this topic
- Topography and Branches of the Trigeminal Nerve (CN V)
- Course of the Caudal Group of Cranial Nerves (CN IX, X, XI, XII)
- Blood Supply to the Dura Mater
- Structure and Functions of Emissary Veins
- Anatomy of Inner Ear Structures (Labyrinth)
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