Transcript 06. venous sinuses

Venous Blood Sinuses
They are blood-filled spaces situated
between the layers of the dura mater.
They are lined by endothelium.
Their walls are thick and composed
of fibrous tissue. They have no
muscular tissue. They have no valves.
They receive tributaries from the
brain; the diploic veins of the skull;
the orbit and the internal ear.
Inferior Sagittal Sinus
It occupies the free lower margin of
the falx cerebri.
It runs backward and joins the great
cerebral vein which is formed by the
union of the 2 internal cerebral veins
at the free margin of the tentorium
cerebelli to form the straight sinus.
It receives cerebral veins from the
medial surface of the cerebral hemisphere.
N.B:
Veins have no valves ; no muscular tissue
in their wall and drain into venous
Superior Sagittal Sinus
It occupies the upper fixed border of the
falx cerebri. It begins in the front at the
foramen cecum where it receives a vein
from the nasal cavity.
It runs backward, grooving the vault of
the skull and at the internal occipital
protuberance it deviates to one side
( usually the right ) and becomes
continuous with the transverse sinus.
It communicates through small openings
with 2 or 3 venous lacunae on each side.
Numerous arachnoid villi and
granulations project into these lacunae
which also receive the diploic; emissary
and meningeal veins.
It receives the superior cerebral veins .
At the internal occipital protuberance it is
dilated to form the confluence of the
sinuses which is connected to the
opposite transverse sinus and receives
the occipital sinus.
Straight Sinus
It occupies the line of
junction of the falx cerebri
with the tentorium cerebelli.
It is formed by the union of
the inferior sagittal sinus with
the great cerebral vein.
It ends by turning to the left
( sometimes to the right ) to
form the transverse sinus.
Occipital Sinus
It is a small sinus occupying the attached margin of the falx cerebelli.
It communicates with the vertebral veins near the foramen magnum.
Superiorly it drains into the confluence of sinuses.
Transverse Sinus
They are paired and begin at the internal occipital protuberance.
The right sinus usually continuous with the superior sagittal sinus.
The left is continuous with the straight sinus.
Each sinus occupies the attached margin of the tentorium cerebelli , grooving the occipital
bone and posteroinferior angle of the parietal bone.
They receive the superior petrosal sinuses; inferior cerebral and cerebellar veins and diploic
veins.
They end by turning downward as the sigmoid sinuses.
Superior and Inferior Petrosal Sinuses
They are small and situated on the superior and inferior borders of the petrous
part of the temporal bone on each side.
Each superior sinus drains the cavernous sinus into the transverse sinus.
Each inferior sinus drains the cavernous sinus into the internal jugular vein.
Sigmoid Sinuses
They are a direct continuation of the transverse sinuses. Each sinus turns
downward and medially and grooves the mastoid part of the temporal bone.
Here it lies behind the mastoid antrum.
It then turns downward through the posterior part of the jugular foramen to
become continuous with the superior bulb of the internal jugular vein.
Cavernous Sinuses
They are situated in the middle cranial fossa on each side of the body of the
sphenoid bone.
Each sinus extends from the superior orbital fissure in front to the apex of the
petrous part of the temporal bone behind.
The 3rd ; 4th cranial nerves and the ophthalmic & maxillary divisions of the
trigeminal nerve run forward in the lateral wall of this sinus. They lie between the
endothelial and the dura mater .
The internal carotid artery, its sympathetic nerve plexus and abducent nerve run
forward through it. They are separated from the blood by an endothelial
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The tributaries are 1- Superior ophthalmic vein which communicates it with the facial V
2- Inferior ophthalmic vein.
3- Cerebral veins
4- Central vein of the retina
5- Sphenopareital sinus.
The sinus drains posteriorly into the superior and inferior petrosal sinuses and
inferiorly into the pterygoid venous plexus.
The 2 sinuses communicate with one another by means of the anterior and
posterior intercavernous sinuses which run in the diaphragma sellae in front and
behind the stalk of the hypophysis cerebri.
Hypophysis Cerebri
The pituitary gland is an edocrine gland. It is
small, oval and attached to the undersurface
of the brain by infundibulum.
It is located in the sella turcica of the
sphenoid bone.
It is divided into an anterior lobe or
adenohypophysis and posterior lobe or
neurohypophysis.
Relations
Superiorly: The diaphragma sellae which has
a central aperture that allows the
passage of the infundibulum. This
sellae separates the anterior lobe
from the optic chiasma. Inferiorly: The
body of the sphenoid with its
sphenoid air sinuses.
Laterally: The
cavernous sinus and its
contents.
Posteriorly: The
dorsum sellae; basilar artery
and
pons.
Blood supply: The superior and inferior
hypophyseal arteries the branches of the
internal carotid artery.
Veins drain into the intercavernous sinuses.
Extradural Hemorrhage
It results from injuries of the meningeal
arteries or veins. The most common is
the anterior branch of the middle
meningeal artery.
A minor blow to the side of the head
result in fracture of the anteroinferior
portion of the parietal bone ( pterion ).
The intracranial pressure rises. The
blood clot exerts local pressure on the
underlying motor area in the precentral
gyrus.
Blood may pass out through the
fracture line to form a soft swelling
under the temporalis muscle.
The burr hole through the skull wall
should be placed 2.5 to 4 cm above the
midpoint of the zygomatic arch to ligate
or plug the torn artery or vein.
Subdural Hemorrhage
It is more common than the middle meningeal artery hemorrhage. It results from tearing of
the superior cerebral veins at their entrance into the superior sagittal sinus.
The cause is a blow on the front or back of the head causing anteroposterior displacement
of the brain within the skull. Blood under low pressure begins to accumulate in the space
between the dura and arachnoid. The case is bilateral in 50 %.
Acute symptoms in the form of vomiting due to rise in the venous pressure may be present.
In the chronic form, over a several months, the small blood clot will attract fluid by osmosis
so a hemorrhagic cyst is formed and gradually expands produces pressure
Intracranial Hemorrhage in the Infant
It occurs during birth and from excessive molding of the head. Bleeding occurs
from cerebral veins or venous sinuses
Excessive anteroposterior compression often tears the anterior attachment of the
falx cerebri from the tentorium cerebelli.
bleeding then takes place from the great cerebral veins; straight sinus or inferior
sagittal sinus.
Subarachnoid Hemorrahage
It results from leakage or rupture of a
congenital aneurysm on the circle of Willis or
less commonly from an angioma.
The sudden symptoms include severe
headache; stiffness of the neck and loss of
consciousness.
The diagnosis is established by withdrawing
heavily blood- stained CSF fluid through a
lumbar puncture ( spinal tap ).
Cerebral Hemorrhage
It is caused rupture of the thin-walled
lenticulostriate artery, a branch of the middle
cerebral artery. The hemorrhage involves the
vital corticobulbar & corticospinal fibers in
the internal capsule and produces hemiplegia
on the opposite side of the body.
The patient immediately loses consciouness
and paralysis is evident when consciousness
regained.