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11.5.2015
http://antranik.org/wp-content/uploads/2011/11/ventricles-of-the-brain-horn-interventricular-foramen.jpg
Kaan Yücel
M.D., Ph.D.
http://fhs122.org
[email protected]
Dr. Kaan Yücel
fhs122.org
Ventricular System, Meninges, Vessels of CNS
CSF (Cerebrospinal fluid, BOS; beyin omurilik sıvısı)
Liquor cerebrospinalis, is a clear, colorless, bodily fluid that occupies the subarachnoid space and the
ventricular system around and inside the brain and spinal cord. In essence, the brain "floats" in it.
It acts as a "cushion" or buffer for the cortex, providing a basic mechanical and immunological protection to
the brain inside the skull. CSF is produced in the brain by choroid plexus (approx. 50-70%), and the remainder is
formed around blood vessels and along ventricular walls. It circulates from the lateral ventricles to the third
ventricle, fourth ventricle,; subarachnoid space over brain and spinal cord. CSF is reabsorbed into venous sinus
blood.
The ventricles are four fluid-filled cavities located within the brain; these are the two lateral ventricles, the
third ventricle, and the fourth ventricle. The two lateral ventricles communicate through the interventricular
foramina (of Monro) with the third ventricle. The third ventricle is connected to the fourth ventricle by the narrow
cerebral aqueduct (aqueduct of Sylvius). The fourth ventricle, in turn, is continuous with the narrow central canal of
the spinal cord and, through the three foramina in its roof, with the subarachnoid space. The connection between
subarachnoid space & the 4th ventricle  1 hole in the middle: median aperture (of Magendi),two holes lateral
apertures (of Luschka)
There are two large lateral ventricles, and one is present in each cerebral hemisphere. It has 4 parts 1)
Anterior (frontal) horn in the frontal lobe, 2) Body, 3) Inferior (temporal) horn in the temporal lobe, 4) Posterior
(occipital) horn in the occipital lobe. It produces 70 % of the CSF in the ventricles. CSF is emptied into superior
sagittal sinuses via arachnoid granulations. See the second Figure below!
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Meninges
The meninges are three connective tissue coverings that surround, protect, and suspend the brain and spinal cord
within the cranial cavity and vertebral canal, respectively:
•Dura mater is the thickest and most external of the coverings;
• Arachnoid mater is against the internal surface of the dura mater;
•Pia mater is adherent to the brain and spinal cord.
Between the arachnoid and pia mater is the subarachnoid space, which contains CSF.
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Dr. Kaan Yücel
fhs122.org
Ventricular System, Meninges, Vessels of CNS
Blood supply
The brain is supplied by the two internal carotid and the two vertebral arteries. The four arteries lie within
the subarachnoid space, and their branches anastomose on the inferior surface of the brain to form the circle of
Willis (cerebral arterial circle).
The two vertebral arteries enter the cranial cavity through the foramen magnum and just inferior to the
pons fuse to form the basilar artery. The two internal carotid arteries enter the cranial cavity through the carotid
canals on either side. The basilar artery, formed by the union of the two vertebral arteries, ascends in a groove on
the anterior surface of the pons. At the upper border of the pons, it divides into the two posterior cerebral arteries.
The internal carotid artery then runs horizontally forward through the cavernous sinus and enters the
subarachnoid space by piercing the arachnoid mater and turns posteriorly to the region of the medial end of the
lateral cerebral fissure. Here, it divides into the anterior and middle cerebral arteries. Anterior communicating
artery connects the two anterior cerebral arteries. Posterior communicating arteriesn are branches of internal
carotid arteries. They connect the posterior cerebral arteries of the basilary arteries to the internal carotid arteries.
The spinal cord receives its arterial supply from three small arteries: the two posterior spinal arteries and
the anterior spinal artery. These longitudinally running arteries are reinforced by small segmentally arranged
arteries that arise from arteries outside the vertebral column and enter the vertebral canal through the
intervertebral foramina.
Venous drainage
Venous drainage of the brain begins internally as networks of small venous channels lead to larger cerebral
veins, cerebellar veins, and veins draining the brainstem, which eventually empty into dural venous sinuses. The
dural venous sinuses eventually lead to the internal jugular veins.
The veins of the brain have no muscular tissue in their very thin walls, and they possess no valves. They
emerge from the brain and lie in the subarachnoid space. They pierce the arachnoid mater and the meningeal layer
of the dura and drain into the cranial venous sinuses.
The superior sagittal sinus (CSF is emptied here), straight sinus, and occipital sinus empty into a common
site: confluence of sinuses, torcular herophili (Herophilus from Kadıköy). It is found under the internal occpital
protuberance. The blood from here drains into the transverse sinus. It then empties into sigmoid sinus. Finally the
venous blood of the brain reaches internal jugular veins on both sides.
The veins of the spinal cord drain into longitudinal channels that communicate superiorly within the skull
with the veins of the brain and the venous sinuses. They drain mainly into the internal vertebral venous plexus.
They have connections with the vertebral vein plexuses. The veins of the spinal cord and vertebral column are
valveless. The tumours of the prostate and breast might reach vertebrae and the brain through the connections of
veins of the vertebral column.
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