Download Region 4: Cranial Contents Calvaria: skull cap -

Region 4: Cranial Contents
Calvaria: skull cap
--Composed of three layers
*Outer table: compact bone
*Diploe: spongy bone containing diploic veins and marrow
*Inner table: compact bone
--Emissary Foramina for emissary veins: emissary veins connect dural venous
sinuses within the cranium with the veins external to it
Meninges: coverings of the brain which are exposed when the calvaria is removed
--Dura mater (tough mother)
*Periosteal layer: fused to bone
*Meningeal Layer: the true layer of dura which reduplicates to form four
projecting folds
a. falx (sickle) cerebri: located b/w cerebral hemispheres
b. falx cerebelli: between cerebellar hemispheres
c. tentorium cerebelli: separates occipital lobes of cerebrum from
cerebellum
d. diaphragma (septum) sellae (saddle): forms roof of sella turcica
*Dural Venous sinuses: lie b/w layers of dura and receive veins draining the
brain to ultimately leave the skull via the interal jugular vein
a. superior sagittal sinuses: along superior border of falx cerebri,
drains into the confluens of the sinuses, unpaired
b. inferior sagital sinus: along the inferior border of the falx cerebri,
unpaired
c. straight sinus: at junction of falx cerebri and tentorium cerebelli,
unpaired, receives the greate cerebral vein of Galen, drains the
inferior sagittal sinus, empties into the confluens of the sinuses
d. intercavernous sinus: in diaphragma sellae, connects the left and
right cavernous sinuses, unpaired
e. transverse sinuses: at attachment of the tentorium cerebelli to skull,
drains into the sigmoid sinus, paired
f. sigmoid sinuses: connect the anterior end of the transverse sinuses
with the interal jugular veins, paired
g. cavernous sinuses: on each side of the sella tursica, paired
h. superior petrosal sinuses: connects the cavernous sinus to the
sigmoid sinus, paired
i. inferior petrosal sinuses: connect the cavernous sinus to the internal
jugular vein, paired
*Cavernous Sinus
a. lies on either side of the body of the sphenoid bone
b. trabeculae from each layer cross the space giving it a cavernous
apperance
c. Contents of the cavernous sinus
--Oculomotor Nerve (CN III)
--Trochlear Nerve (CN IV)
--Ophthalmic Nerve (CN V1)
--Maxillary Nerve (CN V2)
--Internal Carotid Artery
--Abducens Nerve (CN VI)
d. Drains: the superior ophthalmic veins, cerebral veins, and
sphenoparietal veins
--Subdural Space
*space between the arachnoid and dura matter, contains very small amont of
fluid
--Arachnoid Mater
*delicate membrane attached to the pia mater by trabeculae
*arachnoid granulations: project into the dural sinuses to return CSF to the
blood
--Subarachnoid Space
*actual space b/w the arachnoid and pia mater
*filled with CSF (CSF is formed by choroid plexus in the brain’s ventricles)
*communicates with the fourth ventricle of the brain by the median foramen
of Magendie and the 2 lateral foramina of Luschka
--Pia Mater
*clings to the surface of the brain and follows all of its irregularities
--Meningeal Arteries and veins: supply the dura and adjacent bone
*Middle cranial fossa: the middle meningeal artery passes through the
foramen spinosum and it supplies 4/5 of the dura
Brain
--Divisions
a. telencephalon or cerebral hemispheres with the frontal, parietal, temporal,
and occipital lobes
*the olfactory bulb and tract are attached to the frontal lobe and are
associated with the olfactory nerve (CN I)
b. Deiencephalon: includes the thalamus, hypothalamus, optic chiasma (CN
II), pituitary and pineal glands
c. mesencephalon (mid-brain): gives the orging to oculomotor (CN III), and
trochlear nerves (CN IV)
d. metencephalon: consists of the pons and cerebellum
*gives origin to trigeminal nerve (CN V), abducens (CN VI), facial (CN
VII), and vestibulocochlear (CN VIII) nerves
e. myelencephalon (medulla): origins of the glossopharyngeal (CN IX), vagus
(CN X), and the cranial portion of accessory (CN XI) nerves and the
hypoglossal nerve (CN XII) is immediately anterior to the inferior olive
--The brain itself is insensitive to pain.
--Blood Supply to the Brain
a. vertebral arteries: enter the cranial cavity through the forament magnum,
vessels from both sides join to form the basilar artery on front of the pons
*Branches:
--posterior spinal arteries (descend to supply the dorsal side of
the spinal cord)
--anterior spinal arteries (join and descend to supply the
ventral surface of the spinal cord as a single artery)
--posterior inferior cerebellar arteries (supply the cerebellum)
b. Basilar artery: gives off several pairs of arteries before dividing into its
larger paired terminal branches, the posterior cerebral arteries
*Branches:
--anterior inferior cerebellar artery
--superior cerebellar artery
--posterior cerebral artery (terminal branches of the basilar
artery, communicates with the ipsilateral internal carotid
artery by way of the posterior communicating artery)
c. Internal Carotid artery: enters cranial cavity by passing through the carotid
canal and then lying superior to the forament lacerum  then passes
through cavernous sinus, pierces the dura as it gives off the ophthalmic a.
*Branches:
--ophthalmic artery (enters the orbit through the optic
foramen with the optic nerve)
--posterior communicating artery (communicates with
posterior cerebral artery)
--anterior cerebral artery (small of 2 terminal branches,
communicating with each other by way of unpaired anterior
communicating artery)
--middle cerebral artery: largest of the 2 terminal branches
d. Cerebral Circle of Willis
*anterior and posterior communicating arteries indirectly link up the
basilar artery with the interal carotid arteries of both sides
*arteries that make up the circle of Willis
--posterior cerebral arteries
--posterior communicating arteries
--internal carotid arteries
--middle cerebral arteries
--anterior cerebral arteries
--anterior communicating artery