Skull

Anterior and lateral - inner surface of the frontal bone

Posterior - sphenoid bone

Posteromedial - anterior border of the chiasmatic sulcus

Posterolateral - lesser wings of the sphenoid bone

Frontal lobe of the cerebral cortex

Olfactory bulb

Olfactory tract

Orbital gyri

Cribriform foramina (olfactory foramina)

Foramen cecum

Anterior and posterior ethmoidal foramina

Cranial base, Internal cranial base, Anterior cranial fossa, Bones of the anterior cranial fossa — Anterior cranial fossa by Anatomy.app

Middle cranial fossa

The middle cranial fossa lies deeper within the skull base. It is wider than the anterior cranial fossa. It is butterfly-shaped and located in the center of the cranial floor. The middle cranial fossa is made up of sphenoid and temporal bones. The middle cranial fossa is formed by the body and greater wings of the sphenoid, the squamous part of the temporal bone, and the anterior surface of the petrous portion of the temporal bone.

Middle cranial fossa

Anteriorly - anterior margin of the chiasmatic groove, posterior margins of the lesser wings, and part of the body of sphenoid bone

Posteriorly - superior borders of the petrous part of the temporal bones, dorsum sellae of the sphenoid

Laterally - squamous parts of the temporal bones, greater wings of the sphenoid bone, and part of the parietal bones

Pituitary gland

Temporal lobes of the cerebral cortex

Hiatus of the greater petrosal nerve

Optic canal

Superior orbital fissure

Hiatus of the lesser petrosal nerve

Cranial base, Internal cranial base, Middle cranial fossa, Bones of the middle cranial fossa — Middle cranial fossa by Anatomy.app

Posterior cranial fossa

The posterior cranial fossa lies at the lowest level of the internal cranial base and is the largest of the three cranial fossae. It is made of the occipital, temporal, and parietal bones. It is formed by all parts of the occipital bone, the posterior surface of the petrous portion of the temporal bone, and the mastoid angle of the parietal bone.

Posterior cranial fossa

Opening of the vestibular canaliculus

Anteriorly - dorsum sellae, superior margins of the petrous parts of the temporal bones

Posteriorly - squamous part and internal occipital protuberance of the occipital bone, groove for the transverse sinus

Laterally - petrous and mastoid parts of the temporal bones, lateral parts of the occipital bone

Internal acoustic meatus

Cranial base, Internal cranial base, Posterior cranial fossa, Bones of the posterior cranial fossa — Posterior cranial fossa by Anatomy.app

External cranial base

The external cranial base is the outer aspect of the skull base. It extends from the superior incisor teeth to the superior nuchal line of the occipital bone. The external cranial base can be subdivided into anterior, middle, posterior, and two lateral parts.

The anterior part of the external cranial base is comprised of the superior alveolar arch, the bony palate, and the choanae. The alveolar process of the maxilla forms the superior alveolar arch, and it contains the dental alveoli or sockets for the teeth. The bony palate is formed by the palatine process of the maxillae anteriorly and horizontal plates of the palatine bones posteriorly. median palatine suture in the midline, and the frontally oriented transverse palatine suture located between the anterior two-thirds and posterior one-third of the hard palate.

The hard palate forms the roof of the oral cavity and the inferior wall of the nasal cavity. Openings presented on the bony palate include the incisive foramen and greater and lesser palatine foramina. The choana (plural: choanae) is a paired posterior aperture of the nasal cavity that opens into the nasopharynx. It is delimited by the horizontal plate of the palatine bone, a medial plate of the pterygoid process, the body of the sphenoid, and the vomer.

External cranial base — Landmarks of external cranial base by Anatomy.app

The middle part of the external cranial base is formed by the body of the sphenoid, the petrous portion of the temporal bones, and the basilar part of the occipital bone. It extends from the choanae anteriorly to the anterior margin of the foramen magnum posteriorly. The middle part of the external cranial base presents with several openings, including the foramen lacerum, pterygopalatine fissure, foramen ovale, foramen spinosum, and the carotid canal.

The occipital bone mainly forms the posterior part of the external cranial base. It features such openings as the single foramen magnum and the paired jugular foramen, hypoglossal canal, condylar canal, as well small openings - the mastoid canaliculus and the canaliculus for the tympanic nerve.

Each lateral part of the external cranial base consists of the zygomatic arch and the infratemporal fossa anterior, but the mandibular fossa, the tympanic part of the temporal bone, and the styloid and mastoid processes are located posteriorly. The lateral parts of the external cranial base present such openings as the external acoustic meatus, petro-tympanic fissure, stylomastoid foramen, and other smaller apertures.

Temporal fossa

The temporal fossa is a depressed area on each side of the skull bounded by the temporal lines and the zygomatic arch. It is formed by the temporal, sphenoid, parietal, and frontal bones. The temporal fossa is located superiorly to the infratemporal fossa.

Temporal fossa

Anteriorly - frontal process of the zygomatic bone, zygomatic process of the frontal bone

Superiorly and posteriorly - superior and inferior temporal lines

Inferiorly - infratemporal crest on the greater wing of the sphenoid, zygomatic arch

Laterally - temporal fascia

Medially - frontal, parietal, temporal and sphenoid bones

Walls

Anterior - temporal surface of the frontal and zygomatic bones

Medial - temporal surface of the frontal, parietal and temporal bones, and the greater wing of the sphenoid

Lateral - zygomatic arch

Superficial temporal artery

Temporal muscle and fascia

Zygomaticotemporal nerve

Deep temporal nerves

Temporal branch of the facial nerve (CN VII)

Deep temporal arteries

Superior temporal artery

Corresponding veins

Foramina

Zygomaticotemporal foramen

Cranial base, External cranial base, Temporal fossa, Bones of the temporal fossa — Temporal fossa by Anatomy.app

Borders of temporal fossa by Anatomy.app

Infratemporal fossa

The infratemporal fossa is an irregular-shaped space situated on each side of the skull below the temporal fossa and deep to the ramus of the mandible. It is located between the base of the skull, lateral pharyngeal wall, and ramus of the mandible. The infratemporal fossa communicates with the temporal fossa via space to the zygomatic arch. It also communicates with the pterygopalatine fossa via the pterygomaxillary fissure.

Overview of infratemporal fossa by Anatomy.app

Infratemporal fossa

Superiorly - infratemporal surfaces of the temporal bone and the greater wing of the sphenoid

Inferiorly - medial pterygoid muscle

Laterally - zygomatic arch, medial surface and condylar process of the mandibular ramus

Medially - lateral plate of the pterygoid process, tensor veli palatini and superior pharyngeal constrictor muscles

Posteriorly - carotid sheath

Anteriorly - posterior border of the maxillary sinus

Walls

Anterior - infratemporal surface of the maxilla

Superior - infratemporal surface of the greater wing of the sphenoid bone

Lateral - zygomatic arch and ramus of the mandible

Major branches of the mandibular nerve (CN V3)

Chorda tympani

Otic ganglion

Lingual nerve

Buccal nerve

Inferior alveolar nerve

Auriculotemporal nerve

Maxillary artery

Pterygoid venous plexus

Middle meningeal vein

Maxillary vein

Medial pterygoid muscle

Lateral pterygoid muscle

Tendon of the temporal muscle

Alveolar canals or apertures

Foramen ovale

Foramen spinosum

Pterygomaxillary fissure

Inferior orbital fissure

Mandibular foramen

Skull with infratemporal fossa (borders marked in red) — Infratemporal fossa by Anatomy.app

Pterygopalatine fossa

The pterygopalatine fossa, also known as the sphenopalatine fossa, is a cone-shaped, bilateral depression below the apex of the orbit on the lateral side of the skull. It is located between the maxilla anteriorly, the sphenoid bone posteriorly, and the palatine bones.

Overview of pterygopalatine fossa by Anatomy.app

Pterygopalatine fossa

Anteriorly - superomedial part of the infratemporal surface of the maxilla

Posteriorly - root of the pterygoid process and the adjacent anterior surface of the greater wing of the sphenoid bone

Inferiorly - palatine bone

Superiorly - maxillary surface of the greater wing of the sphenoid bone, inferior orbital fissure

Medially - perpendicular plate of the palatine bone, orbital and sphenoidal processes of the palatine bone

Laterally - pterygomaxillary fissure

Posterior superior alveolar nerve

Pterygopalatine ganglion

Maxillary nerve (CN V2)

Lesser palatine nerve

Greater palatine nerve

Part of the maxillary artery

Sphenopalatine artery

Descending palatine artery

Infraorbital artery

Posterior superior alveolar artery

Sphenopalatine foramen

Inferior orbital fissure

Pterygomaxillary fissure

Greater palatine canal

Foramen rotundum

Pterygoid canal

Pharyngeal canal (palatovaginal canal)

Skull with pterygopalatine fossa (boundaries marked in red) — Pterygopalatine fossa by Anatomy.app

Orbit

The orbit or orbital compartment is a pyramid-shaped paired skeletal cavity located in the skull on either side of the root of the nose. Its base opens anteriorly in the central part of the face and next to the midline. Its apex is pointed backward. The orbit is a bony cavity housing and protecting the eye, its appendages, and its accessory structures.

Orbit

Margins

Supraorbital - frontal bone

Medial - frontal process of the maxilla

Lateral - zygomatic processes of the frontal and zygomatic bones

Infraorbital - zygomatic process of the maxilla and zygomatic bone

Walls

Roof of the orbit (superior wall) - supraorbital margin and orbital surface of the frontal bone (anteriorly), orbital plate of the lesser wing of the sphenoid (posteriorly)

Floor of the orbit (inferior wall) - orbital surface of the maxilla (anteromedially), orbital surface of the zygomatic bone, palatine bone (anterolaterally)

Medial - lacrimal bone, orbital plate of the ethmoid, lesser wing of the sphenoid, frontal process of the maxilla

Lateral - frontal process of the zygomatic bone (anteriorly), orbital surface of the greater wing of the sphenoid (posteriorly)

Oculomotor nerve (CN III)

Eyeball

Optic nerve (CN II)

Trochlear nerve (CN IV)

Trigeminal nerve (CN V)

Abducens nerve (CN VI)

Ophthalmic artery

Superior and inferior ophthalmic veins

Lacrimal apparatus

Orbital fascia

Extraocular muscles

Orbital fat