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DIGITAL
NEUROANATOMY
SKULL, MENINGES, AND
SPINAL CORD
George R. Leichnetz, Ph.D. Professor,
Department of Anatomy & Neurobiology
Virginia Commonwealth University
2004
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Skull
Anterior
cranial fossa
holds frontal
lobe
Middle
cranial fossa
holds
temporal
lobe
Posterior
cranial fossa
holds
cerebellum &
brainstem
The interior of the skull
has three depressions:
the anterior, middle,
and posterior cranial
fossae.
Anterior Cranial Fossa
Crista galli
Anterior
Cranial Fossa
Cribriform plate of
ethmoid transmits
olfactory nerves (CN I)
Lesser wing of
sphenoid
Sphenoid Bone
Anterior clinoid
process
Sella turcica holds
pituitary gland
Optic foramen transmits
optic nerve (CN II)
Middle Cranial Fossa
Superior orbital
fissure transmits
oculomotor (III),
trochlear (IV),
and abducens
(VI) nerves, plus
ophthalmic
division of the
trigeminal (V)
nerve
Optic foramen
transmits optic
nerve (II)
Middle
Cranial Fossa
Foramen rotundum
transmits maxillary
division of V
Foramen ovale
transmits
mandibular
division of V
Foramen spinosum
transmits middle
menigeal artery
Internal carotid
foramen transmits
internal carotid
artery
Posterior Cranial Fossa
Sella turcica
Foramen rotundum
Foramen ovale
Foramen
spinosum
Internal auditory
meatus transmits
CN VII and VIII
Internal carotid
foramen and
carotid canal
Petrous ridge of
temporal bone
Foramen
magnum
Sigmoid sinus
Jugular foramen
transmits CN
IX, X, and XI
Hypoglossal
canal transmits
CN XII
Meninges and
Dural Sinuses
The meninges include: dura mater, arachnoid membrane,
and pia mater. The dura consists of two layers: an outer
periosteal layer that forms the periosteum on the inside of
the cranial bone (no epidural space), and an inner layer,
the meningeal layer, that gives rise to dural reflections
(form partitions). The falx cerebri extends into the
longitudinal fissure, separating the cerebral hemispheres.
The tentorium cerebelli extends between the cerebellum/
brainstem and the occipital lobe, forming a roof over the
posterior cranial fossa.
The dural sinuses are endothelial-lined venous channels (“veins”)
between the two layers of the dura. The system of venous channels
ultimately empties into the internal jugular vein at the jugular
foramen. Identify the superior sagittal, inferior sagittal, straight,
transverse, and sigmoid sinuses in the meninges, and their
impressions inside the skull.
Arachnoid villi, knobs protruding into the superior sagittal sinus,
allow reabsorption of CSF into the systemic venous circulation.
Dura Mater
Branches of the middle
meningeal artery supply
the dura
Arachnoid
membrane
Arachnoid Membrane
Subarachnoid
space
Arachnoid Villi
Superior sagittal
sinus
Falx cerebri
Inferior sagittal
sinus
Corpus callosum
Straight sinus
Thalamus
Confluence
of sinuses
Midbrain
Attachment of
falx to crista galli
The dural sinuses are
endothelial-lined venous
channels within the dura.
Cerebellum
Pons
Medulla
Falx cerebri
Midbrain
Clinoid processes
serve as
attachments for
the for the
tentorium
cerebellum
Tentorial Notch or
Incisure
Cerebellum
Tentorium
cerebelli
Tentorium cerebelli
attaches along the
petrous ridge
Attachment of
tentorium cerebelli
along petrous ridge
Midbrain traverses the
opening in the tentorium
cerebelli, the tentorial notch.
Diaphragma sellae has
opening for pituitary stalk
Tentorium cerebelli
Clinoid process
provides
attachment for
tentorium
Straight sinus
Midbrain
Transverse
sinus
Confluence
of sinuses
The brainstem and
cerebellum occupy the
posterior cranial fossa
(infratentorial
compartment).
Cerebellum
Tentorium Cerebelli Removed Revealing Posterior
Cranial Fossa (Cerebellum & Brainstem Removed)
Foramen magnum w
cervical spinal cord,
vertebral arteries
Confluence
of Sinuses
Transverse
Sinus
Spinal Cord
The spinal cord is about 18” in length, extending from the
foramen magnum to vertebral level L2. It expands at levels
that give rise to innervation of the upper and lower limbs,
the cervical and lumbosacral enlargements respectively.
The lower end of the cord tapers to the conus medullaris
below which the pia extends as the filum terminale,
anchoring the cord inferiorly to the coccyx. About twenty
pairs of denticulate ligaments (extensions of pia to dura)
anchor the cord laterally within the dural sac.
The dorsal and ventral rootlets of the spinal nerves exit the
cord horizontally in the cervical region, but at lower levels
of the cord they descend to their intervertebral foramen of
exit, creating the cauda equina.
There are 31 segments of the cord and 31 pairs of spinal nerves (one
pair off each segment). Spinal nerves C1 thru C7 exit above the
vertebra of the same number. C8 exits below vertebra C7. T1 thru
coccyeal 1 exit below the vertebra of the same number.
Cervical Spinal Cord
Dural sac
opened
(dura mater)
Dorsal rootlets emerge
from the dorsolateral
sulcus
Dorsal median
sulcus
Arachnoid
membrane
Ventral median fissure
w ant. spinal artery
Posterior spinal
arteries anastamose
on the dorsal surface
of the cord
Cervical
enlargement
Ventral horn is enlarged
due to origin of nerves to
upper extremity
Thoracic Spinal Cord
Anterior spinal
artery in ventral
median fissure
Dura reflected
Lateral horn
Denticulate
ligaments
(surface pia
penetrates
archnoid to
attach to dura,
anchoring the
cord laterally
Ventral median
fissure
The thoracic cord is more
cylindrical. It has thin Hshaped gray matter, since it
only innervates intercostal
and axial muscles.
Lumbosacral
enlargement
Lumbar & Sacral Spinal Cord
Conus medullaris
Spinal cord ends
at vertebral level
L2
Filum terminale
Lumbar
The dorsal and
ventral nerve
rootlets of lower
cord segment make
up to cauda equina.
Enlarged
ventral horn
due to origin
of nerves to
the lower
extremity
Roots of
cauda
equina
Sacral