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Cerebrospinal fluid: 1- Is the one of the four types of the body fluid (blood, extracellular and intracellular fluid). 2- It's clear watery fluid similar to lymph and has cells, salt, minerals and proteins and few of WBC. 3- It fills the space between the meninges as well as the ventricles chambers and the intercellular space in the wall of the brain and spinal cord and subarachnoid cavity. 4- The function of the CSF are : 1. supplying (nutrition ) to the deep tissue of the brain by transport O2 and ions 2. Having defense mechanism because it is antibacterial, antitoxic and its carrying antibodies and act as lymphatic fluid to the brain tissue. 3. The CSF is act as cushion to the brain from traumatic shock. 5- The CSF is secreted from the choroid plexuses at all ventricles brain. 6- The secretion of CSF is continuously and they excise are absorbed by arachnoid villi to the blood. 7- The CSF can be obtained from the lumber cistern by lumber puncture Flow of the CSF Two lateral ventricles ↓ Inter ventricular foramina ↓ Foramina of Monro ↓ Third ventricle ↓ Cerebral aqueduct of sylvivs ↓ th 4 ventricle ↓ Lateral aperture of Luschka ↓ Cisterna magna ↓ Small amount of CSF go to the central canal of spinal cord and go to all subarachnoid spaces Meninges : protective connective tissue sheaths surrounding the brain and spinal cord. There are three layers of meninges: 1. Dura Mater— the outermost layer consisting of coarse, irregular connective tissue; composed of collagen and elastic fibers. 2. Arachnoid— middle layer of the meninges; it consists of a distinct membrane and numerous fibrous trabeculae on its inner surface. This trabecular network forms the structural framework for the subarachnoid space which lies between the arachnoid proper and the underlying pia mater. The subarachnoid space contains cerebrospinal fluid (CSF). At certain points the subarachnoid space is dilated and forms “cisterns”. The cisterna magna and lumbar cisterns are important clinically because that is where CSF taps are performed. [Note: CSF is a clear colorless fluid that surrounds and permeates the entire central nervous system. It functions to protect, support and nourish the CNS.] 4. Pia Mater—(from the latin term meaning”tender mother”), the innermost layer of the meninges, it forms a thin protective membrane which adheres to the surface of the brain and spinal cord. It consists of flattened fibrocytes superficial to elastic and collagen fine fibers that extends into the numerous depressions and fissures on the surface of the brain and cord. It is very vascular. 5. Cranial meninges: 1Cerebral duramater: is closely united with endosteum of the cranial cavity. The duramater consists of two membranes, an external or endosteal layer and an internal or meninges layer which are closely unite. The meningeal layer is separated from the endosteal layer where the cranial venous sinuses are located between them. The duramater is continuous with sheath of the cranial nerves at foramina through which the nerves enter or leave the cranial cavity and with the spinal duramater at the foramina magnum. The duramater have three folds or processes which separated parts of the brain, they are falx cerebri, the tentorium cerebelli and the diaphragm sella. A-Falx cerebri: is the dorsal mid sagittal, sickle-shaped fold of duramater which extends ventrally between the cerebral hemispheres of the brain. It is attached to the crista galli rostrally and joins the tentorium cerebelli caudally at this site there is straight venous sinus joins the dorsal sagittal sinus caudodorsally. At the convex dorsal midline the two layers of the falx cerebri are separated by the dorsal sagittal venous sinus. The dorsal sagittal sinus is bounded by the endosteum and bone dorsally. (The ventral sagittal venous sinus not found as in man.) B-Tentorium cerebelli: is the transverse partition between the cerebellum and the occipital poles of the cerebral hemisphere. The internal concave border is free and forms the tentorial notch which partially encircles the mesencephalon; the tentorium cerebelli is attached ventrolaterally to the dorsomedially ridge of the petrous part of the temporal bone and contains a part of the dorsal petrosal venous sinus. The tentorium cerebelli blends with the diaphragm sella at the dorsum sellae and forms a portion of the roof over the cavernous venous sinus. At the junction of the tentorium cerebelli with the endosteum of the parietal and occipital bones, the transverse venous sinus is located between the layers of the tentorium and the endosteum. C-Diaphragm sellae: is a horizontal sheet of duramater which bridges the sella turecica. It separated the hypophysis from ventral surface of the diencephalons; the cavernous and intercavernous venous sinuses are covered by the peripheral portions of the diaphragm sellae. 2-Cerebral arachnoid: is a very delicate, thin membrane situated between the duramater and the piamater. It's connected to the piamater by thin connective tissue trabeculae which pass through the subarachnoid cavity. The cerebral arachnoid dose not extends into the sulci on the surface of the bran. In certain location it's separated from the piamater by a considerable distance to form the subarachnoid cisterns which are: A-Cisterna cerebellmedullaris: some time referred to as the cisterna magna and located in the angle formed by the caudal surface of the cerebellum and the dorsal surface of the medulla oblongata, it communicates with the fourth ventricle through the lateral apertures of the latter and with the spinal subarachnoid cavity caudally b- Cisterna fossae lateralis cerebri: located over the area of the lateral cerebral fissure. C-Cisterna chiasmatis: locates rostral to the optic chiasma between the cerebral crura of the mesencephalon. Notes: *the cranial subarachnoid cavity is filled with cerebrospinal fluid (CSF) and is continuous with the spinal canal through the foramena magna. It is communicates with the 4th ventricle via its lateral apertures and if present the median apertures. *the cranial arachnoid has small projection (arachnoid villi) which project through the duramater into the venous sinuses, most of these villi are microscopic in size, however, enlargement of these villi may occur in the large animals, like horse to Form arachnoid granulation, much of CSF passes from the subarachnoid cavity into the venous sinuses via the arachnoid villi. 3-Crebral piamater: is a thin connective tissue membrane that adheres closely to the brain. It receives the arachnoid trabeculae and forms the deep wall of the arachnoid cavity. The piamater is highly vascularized and extends deeply into sulci of the cerebral hemispheres and folia of the cerebellum. The blood vessels penetrating the nervous tissue are surrounded by the piamater and the privascular spaces. The vessels of the piamater are modified increased in number and tortuosity and with the epithelial (ependyma) project in the ventricular cavity forming the choroid plexuses of the respective ventricles.