Interior of the Skull, Cranial Meninges and Related Vasculature

Gross AnatomyInterior of the Skull, Cranial Meninges and Related Vasculature


Anatomy Tables for Today's Topic



Bones
Arteries
Topographic Anatomy
Veins and Dural Venous Sinuses
Meninges


Bones

Bone/Cartilage Structure Description Notes
frontal the anterior bone of the skull which underlies the forehead articulates with the parietal bone posteriorly; zygomatic, ethmoid and sphenoid bones inferiorly; maxilla, nasal and lacrimal bones anteriorly; it is formed from two ossifications centers which normally fuse in the midline - if they do not fuse, a midline "metopic suture" is the result
orbital plate flat portion of frontal that forms the roof of the orbit a very thin portion of the frontal bone which is like an egg shell in thickness
foramen cecum opening near the anterior end of the crista galli transmits an emissary vein which may result in transfer of infectious materials from the nasal cavity to the cranial cavity with resulting meningitis
frontal sinus pneumatized space in the frontal bone usually paired; each drains through the frontonasal duct into the uppermost part of the hiatus semilunaris in the middle nasal meatus
ethmoid delicate bone located between the two orbits highly pneumatized bone that contains the ethmoid air cells; forms the fragile medial wall of the orbit
cribriform plate perforated portion of ethmoid bone on either side of the crista galli perforated for passage of the olfactory nerves
crista galli superior midline projection of the ethmoid bone into the anterior cranial fossa; it arises between the cribriform plates "cock's comb"; anterior anchor point of the falx cerebri
parietal a broad, flat bone forming the lateral surface of the skull paired; this bone articulates with the contralateral parietal bone in the midline at the sagittal suture; it articulates anteriorly with frontal bone at coronal suture; it articulates posteriorly with the occipital bone at the lambdoid suture; it articulates inferiorly with the greater wing of the sphenoid bone at the pterion, the squamous part of the temporal bone at the squamous suture and the mastoid part of the temporal bone at the parietomastoid suture
parietal foramen an opening in the parietal bone located near the sagittal suture it transmits the parietal emissary vein, a valveless vein which connects the scalp to the cranial cavity
granular foveolae small pits located on the inner table of the parietal bone for the arachnoid granulations
occipital the bone forming the posterior surface of the skull it articulates superolaterally with the parietal bones through the lambdoid suture, anteroinferiorly with the temporal bone and anteriorly with the body of the sphenoid bone
squamous part the flat, thin portion of the occipital bone located posterior to the foramen magnum it articulates with the petrous part of the temporal bone anteroinferiorly and the parietal bones superolaterally at the lambdoid suture
lateral part the portion of the occipital bone located lateral to the foramen magnum paired; it is pierced by the hypoglossal canal and the condylar canal
hypoglossal canal an opening in the lateral part of the occipital bone paired; it transmits the hypoglossal nerve
condylar canal an opening in the lateral part of the occipital bone paired; it transmits the condylar emissary vein
occipital condyle a low, wide projection from the inferior surface of the lateral part of the occipital bone paired; it articulates with the atlas
jugular notch a notch located on the anterolateral edge of the lateral part of the occipital bone it forms the posterior margin of the jugular foramen; the temporal bone forms the anterior margin of the jugular foramen
temporal bone forming the lateral side of the skull temporal refers the passage of time, which is marked by the appearance of gray hair on the side of the head
petrous part the hard part of the temporal bone located in the floor of the cranial cavity it contains the tympanic cavity (middle ear) and the bony labyrinth of the inner ear
internal acoustic meatus the opening on the posteromedial surface of the petrous part of the temporal bone it transmits the facial n., the vestibulocochlear n., and the labyrinthine a.
facial canal a canal which courses through the petrous part of the temporal bone it transmits the facial n. from the internal acoustic meatus to the stylomastoid foramen
carotid canal a canal which courses through the petrous part of the temporal bone it transmits the internal carotid a. and the internal carotid plexus of nerves into the cranial cavity
squamous part the thin flat portion of the temporal bone that constitutes the side of the skull above the ear it articulates with the parietal bone and the greater wing of the sphenoid bone at the squamous suture
sphenoid an irregularly shaped bone forming the central portion of the skull it has many parts, including a body, greater wing, lesser wing and pterygoid plates
body central part of the sphenoid bone contains the sphenoid sinuses; attachment point for the wings and pterygoid plates
optic canal canal located at the lateral end of the chiasmatic sulcus and medial to the anterior clinoid process paired; it transmits the optic nerve and the ophthalmic artery from the cranial cavity to the apex of the orbit
tuberculum sellae the anterior limit of the sella turcica the middle clinoid processes project from its lateral ends
sella turcica depression on the superior surface of the body of the sphenoid bone "Turkish saddle"; roughly equivalent to the hypophyseal fossa; area between the tuberculum sellae and the posterior clinoid processes
anterior clinoid process projection at the medial end of the lesser wing of the sphenoid bone the internal carotid artery passes medial to this structure
lesser wing of the sphenoid thin rim of bone projecting laterally from the anterior clinoid process bilateral; it forms the posterior margin of anterior cranial fossa; it articulates anteriorly with the orbital plate of the frontal bone
greater wing of the sphenoid broad plate of bone swinging laterally from the body of the sphenoid bone bilateral; it forms the medial part of the floor of the middle cranial fossa, part of temporal fossae laterally, and the posterior part of the lateral wall of orbit; it articulates anteriorly with the zygomatic bone, superiorly with the frontal & parietal bones (at the pterion), posteriorly with the squamous & petrous portions of the temporal bone
superior orbital fissure slit-like opening between the lesser & greater wings of the sphenoid bone it transmits the oculomotor nerve, the trochlear nerve, the abducens nerve, branches of ophthalmic division of the trigeminal nerve, the superior ophthalmic vein and lymphatics from the cranial cavity into the orbit
foramen rotundum opening in the floor of the middle cranial fossa through the greater wing of the sphenoid bone it transmits the maxillary division of the trigeminal nerve
foramen ovale opening in the floor of the middle cranial fossa through the greater wing of the sphenoid bone it transmits the mandibular division of the trigeminal nerve; it is located between the foramen rotundum and the foramen spinosum
foramen spinosum opening in the floor of the middle cranial fossa through the greater wing of the sphenoid bone it transmits the middle meningeal artery and the meningeal br. of the mandibular division of the trigeminal nerve (cranial nerve V)

Arteries

Artery Source Branches Supply to Notes
basilar formed by the joining of the two vertebral aa. pontine brs., anterior inferior cerebellar a., superior cerebellar a., two posterior cerebral aa. (terminal brs.) pons (motor nucleus of cranial nerve V, chief sensory nucleus of cranial nerve V, abducens nucleus, facial nucleus, superior salivatory nucleus); oculomotor nucleus; nucleus of Edinger-Westphal; cerebellum; posterior cerebrum basilar a. contributes blood to the cerebral arterial circle
carotid, internal common carotid a. none in the neck; in the head: ophthalmic a., posterior communicating a., anterior cerebral a., middle cerebral a. brain; eye and orbit; forehead internal carotid a. is the primary blood supply to the brain; it anastomoses with the vertebral aa. and the contralateral internal carotid a. in the cerebral arterial circle (of Willis); anterior and middle cerebral aa. are the terminal brs. of the internal carotid a.
meningeal, middle maxillary a. frontal br., parietal br., petrous br., superior tympanic br. most of the dura mater (approx. 80%), bones of the cranial vault middle meningeal a. passes through the foramen spinosum; it may be torn by a fracture at the pterion; it is encircled by the auriculotemporal n.
vertebral subclavian a.(1st part) spinal brs., muscular brs., anterior spinal a., posterior inferior cerebellar a., medullary brs., meningeal brs., basilar a. deep neck, cervical spinal cord, spinal cord; medulla (dorsal motor nucleus of cranial nerve X, nucleus ambiguus, spinal accessory nucleus and hypoglossal nucleus) vertebral a. anastomoses with the internal carotid a. in the cerebral arterial circle (of Willis); it courses through the transverse foramina of vertebrae C1-C6

Veins and Dural Venous Sinuses

Vein Tributaries Drains Into Regions Drained Notes
basilar venous plexus superior and inferior petrosal sinuses internal vertebral venous plexus cavernous sinus basilar venous plexus is variable; it communicates connects with other small intracranial sinuses that are located nearby
cavernous sinus superior ophthalmic v., cerebral vv., sphenoparietal sinus superior petrosal sinus, inferior petrosal sinus orbit, brain cavernous sinus lies between the cranial and meningeal layers of the dura mater beside the body of the sphenoid bone; cranial nn. III, IV and V1 are in its lateral wall; the internal carotid a. and cranial n. VI are in its lumen
cerebral, great formed by the union of the paired internal cerebral vv. straight sinus deep portions of the cerebrum great cerebral v. is a very short vessel
cerebral, superior tributaries are unnamed superior sagittal sinus superior aspect of the cerebral hemispheres superior cerebral vv. bleed into the subdural space when injured, resulting in a subdural hematoma; also known as: bridging vv.
confluens of sinuses formed by the joining of the superior sagittal sinus, straight sinus and occipital sinus transverse sinuses all parts of the brain confluens of sinuses lies on the inner surface of the occipital bone; it is between the layers of dura at the junction of the falx cerebri and tentorium cerebelli
diploic vv. multiple veins draining the diploe of the skull: frontal diploic, anterior temporal diploic, posterior temporal diploic, occipital diploic meningeal vv.; dural venous sinuses; veins of the scalp bones of the cranial vault diploic vv. connect the venous system of the scalp with the dural sinuses and meningeal vv.
emissary vv. veins of the scalp veins of the scalp; dural venous sinuses scalp emissary vv. are valveless and can carry blood from superficial to deep or in the reverse direction depending on blood pressure; may carry superficial infectious materials into the dural venous sinuses; there are 4 named emissary vv.: parietal, mastoid, occipital and condyloid; superior ophthalmic v. also acts as an emissary v.
inferior petrosal sinus cavernous sinus sigmoid sinus, at its distal end all regions drained by the cavernous sinus, including the orbit and brain inferior petrosal sinus lies within the dura mater along the inferior portion of the petrous part of the temporal bone
inferior sagittal sinus unnamed tributaries from the falx cerebri and cerebral hemispheres unites with the great cerebral v. to form the straight sinus medial surfaces fo the cerebral hemispheres inferior sagittal sinus is directly superior to the corpus callosum in the free margin of falx cerebri
internal jugular v. formed at the base of the skull where the sigmoid sinus ends; tributaries: pharyngeal vv.; lingual v., common facial v., sternocleidomastoid v., superior thyroid v, middle thyroid v. brachiocephalic v. brain, cranial cavity, skull, face, viscera of the neck internal jugular is the largest vein of the nead and neck
occipital sinus no named tributaries confluens of sinuses cerebellum lies within the dura mater at the base of the falx cerebelli
sigmoid sinus transverse sinus, superior petrosal sinus internal jugular v. brain; meninges sigmoid sinus lies within the sigmoid groove covered by dura mater
straight sinus inferior sagittal sinus, great cerebral vein, superior cerebellar vv. confluens of sinuses deep parts of the cerebrum, cerebellum straight sinus lies within the junction of the falx cerebri and tentorium cerebelli; also known as: sinus rectus
superior petrosal sinus cavernous sinus sigmoid sinus, at its proximal end all regions drained by the cavernous sinus, including the orbit and brain superior petrosal sinus lies on the petrous ridge within the dura mater at the line of attachment of the tentorium cerebelli
superior sagittal sinus v. of the foramen cecum; superior cerebral vv. confluens of sinuses cerebral hemispheres superior sagittal sinus occupies the superior part of the falx cerebri; lateral lacunae receive grossly visible arachnoid granulations
transverse sinus confluens of sinuses, inferior cerebral vv. sigmoid sinus brain lies within the line of attachment of the tentorium cerebelli to the inner surface of the calvaria

Topographic Anatomy

Structure/Space Description/Boundaries Significance
cranial fossa, anterior boundaries: anterior - inner surface of the frontal bone; posterior - posterior edge of the lesser wing of the sphenoid bone frontal lobes of the brain are located within the anterior cranial fossa; cranial nerve I exits the cranial cavity here
cranial fossa, middle boundaries: anterior - posterior edge of the lesser wing of the sphenoid bone; posterior - petrous ridge of the temporal bone temporal lobes of the brain and pituitary gland are located within the middle cranial fossa; cranial nerves II, III, IV, V and VI exit the cranial cavity here
cranial fossa, posterior boundaries: anterior - petrous ridge of the temporal bone; posterior - inner surface of the occipital bone cerebellum and brainstem are located within the posterior cranial fossa; cranial nerves VII, VIII, IX, X, XI and XII exit the cranial cavity here

Meninges

Structure Location/Description Notes
arachnoid mater intermediate one of the three layers of meninges arachnoid mater is a thin membrane which is pressed against the inner surface of the dura mater by cerebrospinal fluid pressure; arachnids are spiders, the space deep to this layer (subarachnoid space) has a spider web-like appearance
dura mater outermost of the meningeal layers covering the brain and spinal cord "tough mother"; it is the most durable of the meninges and provides support and protection for the brain and spinal cord; two types are described which differ in structure: cranial and spinal
dura mater, cranial outermost of the meningeal layers covering the brain; it has 2 layers: periosteal (outer layer) and meningeal (inner layer) cranial dura mater participates in the formation of the dural venous sinuses; it forms infoldings between portions of the brain that help to support the brain: falx cerebri, falx cerebelli, tentorium cerebelli, diaphragma sellae
dura mater, meningeal inner layer of the cranial dura mater dural venous sinuses lie between layers of the cranial dura mater; the meningeal layer forms folds that help to support the brain: falx cerebri, falx cerebelli, tentorium cerebelli
dura mater, periosteal outer layer of the cranial dura mater the periosteal layer of cranial dura mater attaches loosely to the inner surface of the cranial cavity; equivalent to periosteum of the cranial bones; participates in the formation of the dural venous sinuses
dura mater, spinal outermost covering of the spinal cord, it forms the dural sac containing the spinal cord within vertebral canal dural sac ends at S2, coccygeal ligament (filum terminale externum) continues inferiorly to attach to coccyx
epidural space the space external to the sac of spinal dura mater within the vertebral canal the epidural space contains epidural fat and the internal vertebral plexus of veins which is valveless (clinically relevant)
falx cerebri crescent-shaped fold of dura mater located in the sagittal plane falx cerebri lies between the cerebral hemispheres
falx cerebelli small, crescent-shaped fold of dura mater located in the sagittal plane falx cerebelli lies between the cerebellar hemispheres, but does not pass deeply between them
meninges three layers of connective tissue covering the brain and spinal cord; dura mater, arachnoid mater, and pia mater meninges provide protection and nourishment of the brain, brainstem and spinal cord
pia mater delicate membrane that lies on the surface of the brain and spinal cord "delicate mother", it is the most delicate of the meninges; this layer faithfully follows all surface contours of the brain and spinal cord; pia mater has 2 specializations: denticulate ligament and filum terminale internum
tentorium cerebelli tent-like sheet of dura mater covering the superior surface of the cerebellum, oriented somewhat transversely the midbrain passes through the tentorial notch


Other Tables of Interest:

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Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

Content of these tables has been edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2007, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences.

Unauthorized use is prohibited.