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Three layers called the meninges encase the mind and spinal cord. From superficial come deep, these layers are the dura mater, arachnoid mater, and also pia mater. The dura mater is a dense connective organization layer the is adherent to the inner surface of the skull. Next is the arachnoid mater the is a slim impermeable layer, and the innermost is the pia mater, i beg your pardon is a vascular layer that closely invests end the brain and spinal cord.<1> These membranes define three potential clinically significant spaces: the epidural space, i beg your pardon exists between the skull and the dura mater; the subdural space, found between the dura mater and also arachnoid mater; and also the subarachnoid space, which is between the arachnoid mater and pia mater. The epidural space in the skull is a potential space, while it is actually present in the spinal cord. The subarachnoid space consists the the cerebrospinal liquid (CSF), significant blood vessels, and cisterns. The cisterns room enlarged pockets that CSF developed due come the separation that the arachnoid mater from the pia mater based upon the anatomy that the brain and spinal cord surface. The cisterns are produced due come the close and also firm follow of the pia mater to the brain and spinal cord surface while rather loosely to the arachnoid mater.
Structure and Function
Anatomically, the subarachnoid space exists in between the arachnoid mater externally and pia mater internally. A network the fine breakable connective tissue dubbed trabeculae associate these 2 layers and also gives this space its characteristic spider web appearance. The subarachnoid trabeculae act together supportive pillars in between the pia mater and also arachnoid mater, and also due come the curtain-like structure with holes, it allows the circulation of CSF.<2> Besides trabeculae, over there are significant cerebral blood vessels that penetrate the nervous organization within this space.
The subarachnoid an are does not have actually a uniform depth across the central nervous system and also forms extensions approximately the neurovascular structures, spaces, and also cisterns. It forms sleeve-like extensions around the cranial and spinal nerves and terminates wherein the pia mater and the arachnoid mater fuses v the perineum of these nerves. Besides, this an are surrounds the arteries and also veins of the main nervous mechanism up to the allude where they permeate the worried tissue and divide right into arterioles and also venules. If the pia mater very closely adheres come the surface of the mind and adheres to the contours of cortical sulci and also gyri, the arachnoid mater only bridges end the sulci, bring about the development of CSF filled triangular spaces. Also, in ~ some areas where the brain draws away from the skull due to the fact that of its organic variation in shape, the arachnoid mater and the pia mater are not in near approximation. This outcomes in normally enlarged CSF to fill expansions dubbed the subarachnoid cisterns. These expansions transmit intracranial vessels together with cranial nerves and hold far-ranging clinical relevance.<3> Although theses cisterns are commonly described as separate compartments, they room not truly anatomically separate. They room in complimentary communication v each other and with the remainder of the subarachnoid space. Some significant cisterns include<4>:
1) Cistern that the lamina terminalis:
It is situated anterior to the third ventricle and contains the anterior cerebral arteries, the anterior interacting artery, the hypothalamic artery, Heubner"s artery, and also the origin of the fronto-orbital arteries.
2) Sylvian cistern:
Also recognized as the insular cistern, is discovered in the fissure in between the temporal and also frontal lobes. It consists of the middle cerebral artery and also vein and also the fronto-orbital veins.
3) Suprasellar cistern:
Also known as the chiasmatic cistern contains the anterior element of the optic chiasm, optic nerves (cranial nerve II), the hypophyseal stalk, and the origin of the anterior cerebral artery.
4) Interpeduncular cistern
Located between the 2 cerebral peduncles of the midbrain. It communicates inferiorly with the pontine cistern and also superiorly through the chiasmatic cistern and contains the bifurcation that the basilar artery, peduncular sections of the posterior cerebral artery and superior cerebellar artery, the posterior communicating arteries that affix with the peduncular segment of the posterior cerebral arteries, the basal vein and also the oculomotor nerve (cranial nerve III).
5) Superior cistern
Located posterolateral come the midbrain. That lateral extensions attach it to the interpeduncular cistern. That contains the great cerebral vein, the third part of the posterior cerebral arteries and also the superior cerebellar arteries. That is infratentorial portion contains the trochlear nerve (cranial nerve IV).
6) Pontine cistern:
It is located anterior come the pons and also receives CSF from the paired foramen that Luschka (lateral aperture) the the fourth ventricle. It has the basilar artery, the beginning of the anterior inferior cerebellar artery, the beginning of the remarkable cerebellar artery, and also the abducens nerve (cranial nerve VI).
7) Cerebellopontine cistern:
Situated in the lateral angle in between the pons and the cerebellum. It includes the face nerve (cranial nerve VII), the vestibulocochlear nerve (cranial nerve VIII), the trigeminal nerve (cranial nerve V), and the anterior worse cerebellar artery.
8) Cerebellomedullary cistern:
Also recognized as the cisterna magna is the largest subarachnoid cistern. That is located in between the medulla oblongata and the cerebellum. That receives CSF indigenous the 4th ventricle through foramen that Magendie (median aperture). It has the vertebral artery, the origin of the posterior worse cerebellar artery, the glossopharyngeal nerve (cranial nerve IX), vagus nerve (cranial nerve X), accessory nerve (cranial nerve XI) and hypoglossal nerve (cranial nerve XII).
9) Lumbar cistern:
It is situated at the reduced lumbar spinal canal. The extends from the conus medullaris around the level of the very first and 2nd lumbar vertebrae come the level of the 2nd sacral vertebra. It consists of the filum terminale and the cauda equina. Throughout lumbar puncture, the clinician color etc CSF native this cistern.
Functionally, the CSF operation within the subarachnoid an are and the ventricular system. The choroid plexus mainly secretes the cerebrospinal fluid at a rate of 0.3 ml/min, and also there are around 150 ml that CSF circulating at any given time.<5> While the ventricular system includes 25 mL, the remainder is existing within the subarachnoid space. A smaller sized amount of CSF is also secreted through the ependymal lining that the ventricles and also the dura mater that the nerve roots sleeves in the spinal canal.<3> After production, CSF operation from the lateral ventricles through the left and right foramen that Monro and also enters the third ventricle. Next, that flows into the 4th ventricle with the cerebral aqueduct. After that, CSF flows into the subarachnoid space through the foramen of Lushka laterally and also foramen of Magendie medially. It operation superiorly and inferiorly overlying the cerebral cortex and spinal cord.
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<6> Eventually, the reaches the arachnoid granulations that room projections that the arachnoid mater into the superior sagittal sinus and also act as an avenue because that reabsorption that CSF into the blood v a pressure-dependent gradient.