Interior of the skull

Reading File

Finding Sources

Searching Images

interior of skull base cranial fossae anatomy

Finding Sources

Loading Image

Reading File

Searching Images

cranial fossae foramina bones internal skull base labeled diagram

Reading File

Loading Image

Reading File

Loading Image

Reading File

Loading Image

Here is a comprehensive overview of the interior of the skull based on Gray's Anatomy for Students.

Overview

The floor of the cranial cavity is divided into three stepped fossae — anterior, middle, and posterior — each progressively deeper and each accommodating specific brain structures and transmitting distinct neurovascular bundles.

3D CT reconstruction — superior (internal) view of the skull base showing all three cranial fossae with key landmarks labeled

1. Anterior Cranial Fossa

Bones: Frontal (anterior & lateral floor), ethmoid (midline), and sphenoid — body + lesser wings (posterior floor).

Anterior cranial fossa — labeled diagram showing frontal crest, crista galli, cribriform plate, and anterior clinoid processes

Key features:

Frontal crest — midline anterior bony ridge; attachment for the falx cerebri
Foramen cecum — between frontal and ethmoid bones; may transmit emissary veins to the superior sagittal sinus
Crista galli — midline ethmoid projection; falx cerebri attachment
Cribriform plate — sieve-like; transmits olfactory nerve [CN I] fibers from nasal mucosa to olfactory bulb
Orbital plates of frontal bone — thin; also form the roof of the orbit
Lesser wings of sphenoid — form the posterior boundary; end medially as anterior clinoid processes (tentorium cerebelli attachment)

Contents: Frontal lobes of the cerebral hemispheres sit in this fossa, which lies above the nasal cavity and orbits.

2. Middle Cranial Fossa

Bones: Body and greater wings of the sphenoid, squamous and petrous parts of the temporal bone.

Middle cranial fossa — detailed labeled diagram showing sella turcica, optic canals, foramina rotundum/ovale/spinosum, carotid canal, tegmen tympani

Key features:

Structure	Detail
Sella turcica	Hypophyseal fossa (contains pituitary gland); bounded anteriorly by tuberculum sellae and posteriorly by dorsum sellae with posterior clinoid processes
Prechiasmatic sulcus	Groove between optic canals; marks the anterior boundary with the anterior fossa
Optic canal	In lesser wing; transmits CN II + ophthalmic artery
Superior orbital fissure	Between greater and lesser sphenoid wings; transmits CN III, IV, V₁, VI + ophthalmic veins
Foramen rotundum	Transmits CN V₂ (maxillary nerve) → pterygopalatine fossa
Foramen ovale	Transmits CN V₃ (mandibular nerve) + lesser petrosal nerve → infratemporal fossa
Foramen spinosum	Transmits middle meningeal artery (groove visible on inner skull surface)
Carotid canal opening	Internal carotid artery enters the cranium here
Foramen lacerum	Filled by fibrocartilage in life; internal carotid artery passes over it
Hiatus for greater petrosal nerve	On anterior petrous surface
Hiatus for lesser petrosal nerve	Also on anterior petrous surface
Arcuate eminence	Raised area on petrous bone overlying the superior semicircular canal
Tegmen tympani	Thin bony roof of the middle ear cavity

Contents: Temporal lobes of the brain.

3. Posterior Cranial Fossa

The largest and deepest fossa. Bones: Primarily occipital and temporal (petrous/mastoid parts), with minor contributions from sphenoid and parietal.

Posterior cranial fossa — labeled diagram showing foramen magnum, internal acoustic meatus, jugular foramen, hypoglossal canal, internal occipital protuberance, grooves for sinuses

Key features:

Structure	Contents
Foramen magnum	Brainstem/spinal cord junction; vertebral arteries; spinal roots of CN XI; meninges
Clivus	Slope of sphenoid + basilar occipital bone rising from foramen magnum; supports the pons and medulla
Internal acoustic meatus	CN VII (facial), CN VIII (vestibulocochlear) + labyrinthine artery
Jugular foramen	CN IX, X, XI; sigmoid sinus → internal jugular vein; inferior petrosal sinus
Hypoglossal canal	CN XII + meningeal branch of ascending pharyngeal artery
Condylar canal	Emissary vein
Groove for inferior petrosal sinus	Between basilar occipital and petrous temporal bone
Groove for sigmoid sinus	Leads to jugular foramen
Groove for transverse sinus	Runs along posterior occipital bone at internal occipital protuberance
Internal occipital protuberance	Central posterior landmark; convergence of venous sinuses
Internal occipital crest	Midline ridge; attachment for falx cerebelli

Contents: Brainstem (midbrain, pons, medulla) and cerebellum.

Summary Table: Foramina and Transmissions

Foramen	Fossa	Contents
Foramen cecum	Anterior	Emissary veins (nasal → sagittal sinus)
Cribriform foramina	Anterior	CN I (olfactory nerve fibers)
Optic canal	Middle	CN II + ophthalmic artery
Superior orbital fissure	Middle	CN III, IV, V₁, VI + ophthalmic veins
Foramen rotundum	Middle	CN V₂
Foramen ovale	Middle	CN V₃ + lesser petrosal nerve
Foramen spinosum	Middle	Middle meningeal artery
Foramen magnum	Posterior	Spinal cord, vertebral arteries, CN XI spinal roots
Internal acoustic meatus	Posterior	CN VII, VIII + labyrinthine artery
Jugular foramen	Posterior	CN IX, X, XI; sigmoid & inferior petrosal sinuses
Hypoglossal canal	Posterior	CN XII

Gray's Anatomy for Students, pp. 1002–1005

This is a shared conversation. Sign in to Orris to start your own chat.