The document summarizes the bones and landmarks of the cranial cavity, as well as the three cranial fossae - anterior, middle, and posterior. It describes the shape, location and boundaries of each fossa, as well as the key structures that pass through openings in each fossa, such as cranial nerves, blood vessels, and parts of the brain. Important skull landmarks are also defined, such as the pterion, lambda, bregma, vertex and inion.

1. Bones of the Cranial Cavity
Nyra E. Montera
Nov. 11, 2008

5. • Important Landmarks on the Skull
• Fossae and Foramen at the base of
the skull
=> external aspect
=> internal aspect

6. Landmark Shape and Location
Pterion (G. wing)
Junction of the greater wing of the sphenoid,
squamous temporal, frontal, and parietal bones;
overlies course of anterior division of middle
meningeal artery
Lambda (G. the letter L)
Point on calvaria at junction of lambdoid and sagittal
sutures
Bregma (G. forepart of the head)
Point on calvaria at junction of coronal and sagittal
sutures
Vertex (L. whirl or whorl)
Superior point of neurocranium in the midline with
skull oriented in anatomical (orbitorneal or Frankport)
plane
Asterion (G. asterios, starry)
Star-shaped; located at junction of three sutures;
parietomastoid, occipitomastoid, and lambdoid
Glabella (L. smooth, hairless)
Smooth prominence, most marked in males, on the
frontal bone superior to the root of nose; most anterior
projecting part of forehead
Nasion (L. nose)
Point on skull where frontonasal and internasal sutures
meet
Inion (G. back of head)
Most prominent point of external occipital
protuberance

11. glabella

14. External Aspect of the Base of
the Skull

17. Internal Aspect of the Base of
the Skull

18. Anterior cranial fossa
Posterior cranial fossa
Middle cranial fossa

20. ⇒the shallowest of the three fossae.
⇒formed by the
anteriorly: frontal bone
middle: the ethmoid bone,
posteriorly: the body and lesser wings
of the sphenoid.
⇒The greater part of this fossa is formed by the
ridged orbital parts of the frontal bone which
support the frontal lobes of the brain and form
the roofs of the orbits
Anterior cranial fossa

21. Anterior Cranial Fossa Contents
Foramen cecum
Nasal emissary vein (1%
of the population)
Foramina in cribriform
plate
Axons of olfactory cells
in olfactory epithelium
that form olfactory
nerves
Anterior and posterior
ethmoidal foramina
Vessels and nerves with
same names

23. Middle cranial fossa
⇒butterfly-shaped
⇒Posteroinferior to the anterior cranial fossa
⇒The bones forming the fossa are:
laterally: greater wings of the
sphenoid bone
posteriorly: the petrous parts of the
temporal bones
⇒Supports the temporal lobes of the brain

24. Middle Cranial Fossa Contents
Optic canal Optic nerves (CN II) and ophthalmic arteries
Superior orbital
fissures
Ophthalmic veins, ophthalmic nerve (CN V1
),
CN III, IV, and VI, and sympathetic fibers
Foramen rotundum Maxillary nerve (CN V2
)
Foramen ovale
Mandibular nerve (CN V3
) and accessory
meningeal artery
Foramen spinosum
Middle meningeal artery and vein and
meningeal branch of CN V3
Foramen lacerum
Internal carotid artery and its accompanying
sympathetic and venous plexuses
Groove or hiatus of
greater petrosal nerve
Greater petrosal nerve and petrosal branch of
middle meningeal artery

28. Posterior cranial fossa
⇒the largest and deepest of the three
fossae
⇒Lodges the cerebellum, pons and medulla
oblongata
⇒Anteriorly: it extends to the apex of the petrous
temporal.
Posteriorly: it is enclosed by the occipital bone.
Laterally: portions of the squamous temporal
and mastoid part of the temporal bone form its
walls.

29. Posterior Cranial Fossa Contents
Foramen magnum
Medulla and meninges, vertebral arteries,
spinal roots of CN XI, dural veins, anterior
and posterior spinal arteries
Jugular foramen
CNs IX, X, and XI, superior bulb of internal
jugular vein, inferior petrosal and sigmoid
sinuses, and meningeal branches of ascending
pharyngeal and occipital arteries
Hypoglossal canal Hypoglossal nerve (CN XII)
Condylar canal
Emissary vein that passes from sigmoid sinus
to vertebral veins in neck
Mastoid foramen
Mastoid emissary vein from sigmoid sinus
and meningeal branch of occipital artery

32. Special thanks to:
Dalley and Moore, clinically oriented
anatomy 5th
edition,(lippincott williams and
wilkins, 2000), 841-847.