External surface of the base of the skull - elements, passing through the openings and canals

external cranial base

- the outer/ inferior aspect of the skull base

- extends from the superior incisor teeth to the superior nuchal lines of the occipital bone

- subdivided into anterior, middle and posterior parts

anterior part of the external cranial base

made of the

- superior alveolar arch

- bony palate

- choanae

superior alveolar arch

- formed by the alveolar processes of the maxilla

- contains dental alveoli/ sockets for the teeth

choana

- the paired posterior aperture of the nasal cavity that opens into the nasopharynx

- located in the anterior part of the external cranial base

bony palate

- formed by the palatine process of the maxillae anteriorly, the horizontal plates of the palatine bones posteriorly

- forms the roof of the oral cavity and the floor of the nasal cavity (basically the skeleton of the hard palate)

- there's several openings in the bony palate

the openings in the bony palate:

- incisive foramen

- greater palatine foramen

- lesser palatine foramen

- small foramina

incisive foramen

receives the nasopalatine nerves from the floor of the nasal cavity along with the sphenopalatine artery

greater palatine foramen

transmits greater palatine nerve & vessels to the palate

lesser palatine foramen

transmits lesser palatine nerve & vessels

small foramina in the bony palate

for ducts of palatine glands

middle part of the external cranial base

- formed by the body of the sphenoid bone, the petrous parts of the temporal bones and the basal parts of the occipital

- there's several openings

several openings of the middle part of the external cranial base

- foramen lacerum

- pterygomaxillary fissure

- foramen ovale

- foramen spinosum

- carotid canal

foramen lacerum

- formed by the sphenoid and temporal bone

- transmits the artery & nerve of the pterygoid canal

pterygomaxillary fissure

- connects external cranial base & infratemporal fossa with the pterygopalatine fossa

foramen ovale

- located on the greater wing of the sphenoid bone

- transmits the mandibular nerve, the lesser petrosal nerve and an emissary vein

foramen spinosum

- located on the greater wing of the sphenoid bone & is posterior to the foramen ovale

- transmits the middle meningeal artery & meningeal branch of the mandibular nerve

carotid canal

- found on the inferior surface of the petrous part of the temporal bone

- transmits the internal carotid artery, meningeal branches of the ascending pharyngeal artery

posterior part of the external cranial base

-formed by the occipital bone

- there's several openings

several openings of the posterior part of the external cranial base

- foramen magnum

- jugular foramen

- hypoglossal canal

- condylar canal

- mastoid canaliculus

foramen magnum

- largest opening on the occipital bone

- transmits the lower end of the medulla oblongata, the meninges, vertebral arteries and the spinal accessory nerve

jugular foramen

- formed between the occipital and petrous part of the occipital bone

- transmits the inferior petrosal sinus, the glossopharyngeal, vagus & accessory cranial nerves (CN 9-11) and internal jugular vein

hypoglossal canal

- located on inner side of the basilar part of occipital, near the clivius

- transmits the hypoglossal nerve (CN 12) and a meningeal branch of the ascending pharyngeal artery

condylar canal

- located on occipital bone posterior to the occipital condyles

- it's mainly a connection between the external cranial base and the posterior cranial fossa

mastoid canaliculus

- a small canal located on the lateral part of the jugular fossa of temporal bone

- serves as entrance for auricular branch of the vagus nerve (CN10) into the mastoid process