Download Cerebrospinal fluid

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.