ANATOMY OF THE MENINGES, CNS CAVITIES & CSF CIRCULATION Prof. Mujahid Khan اسم ورقم المقرر – Course Name and No. 6/27/2019

Meninges of Brain The brain in the skull and spinal cord in the vertebral column are surrounded by three protective membranes called meninges Dura mater Arachnoid mater Pia mater اسم ورقم المقرر – Course Name and No. 6/27/2019

Dura Mater Dura mater of the brain is described as two layers , the endosteal layer and meningeal layer Endosteal layer is a periosteum covering the inner surface of the skull bones At the foramen magnum it does not become continuous with the dura mater of the spinal cord Around margins of all the foramina in the skull it becomes continuous with the outside periosteum of skull bones اسم ورقم المقرر – Course Name and No. 6/27/2019

Dura Mater Meningeal layer is the dura mater proper It is a dense fibrous membrane covering the brain It is continuous through the foramen magnum with the dura mater of the spinal cord It provides tubular sheaths for the cranial nerves as nerves pass through the foramina of the skull Outside the skull the sheaths fuse with the epineurium of the nerves اسم ورقم المقرر – Course Name and No. 6/27/2019

Dura Mater The meningeal layer sends four septa which divides cranial cavity into freely communicating spaces that lodges the subdivisions of the brain Function of these septa restrict the displacement of the brain when the head is moved Falx cerebri is a sickle shaped fold of dura mater that lie in the midline between the two cerebral hemispheres اسم ورقم المقرر – Course Name and No. 6/27/2019

Dura Mater Its narrow anterior end is attached to the internal frontal crest and crista galli Its broad posterior part blends in the midline with the upper surface of the tentorium cerebelli Superior sagittal sinus runs in its upper fixed margin Inferior sagittal sinus runs in lower concave free margin Straight sinus runs along its attachment to the tentorium cerebelli اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Dura Mater Tentorium cerebelli is a crescent shaped fold of dura mater that roofs over the posterior cranial fossa It covers the upper surface of the cerebellum It supports the occipital lobes of the cerebral hemispheres In the anterior edge there is a gap called tentorial notch for the passage of the midbrain Its fixed border is attached to the posterior clinoid processes اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Dura Mater The falx cerebri and falx cerebelli are attached to the upper and lower surfaces of the tentorium respectively Transverse sinus runs along its attachment to the occipital bone Falx cerebelli is a small sickle shaped fold of dura mater attached to the internal occipital crest and projects forward between the two cerebellar hemispheres Its posterior fixed margin contains the occipital sinus The dura possesses numerous sensory endings that are sensitive to stretching which produce sensation of headache اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Dural Arterial Supply Various arteries supply the dura mater from the internal carotid, maxillary, ascending pharyngeal, occipital and vertebral arteries Clinically important is middle meningeal artery can be damaged in the head injuries اسم ورقم المقرر – Course Name and No. 6/27/2019

Dural Venous Sinuses Venous sinuses of the cranial cavity are situated between the layers of dura mater Their main function is to receive blood from the brain through the cerebral veins and CSF from the subarachnoid space through the arachnoid villi The blood from the dural sinuses drains into the internal jugular veins in the neck اسم ورقم المقرر – Course Name and No. 6/27/2019

Arachnoid Mater Arachnoid mater is a delicate impermeable membrane covering the brain It lies between the pia mater internally and dura mater externally It is separated from the dura by a subdural space It is separated from pia by the subarachnoid space which is filled with cerebrospinal fluid اسم ورقم المقرر – Course Name and No. 6/27/2019

Arachnoid Mater In certain areas the arachnoid projects into the venous sinuses to form arachnoid villi Arachnoid villi serve as sites where the cerebrospinal fluid diffuses into the bloodstream Structures passing to and from the brain to the skull or its foramina must pass through the subarachnoid space All the cerebral arteries, veins and cranial nerves lie in the space اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Pia Mater It is a vascular membrane closely invests the brain, covering the gyri and deepest sulci Cerebral arteries entering the brain substance carry a sheath of pia with them Pia mater forms tela choroidea of roof of third ventricle It fuses with ependymal to form the choroid plexus اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid Cerebrospinal fluid is formed by the choroid plexuses within the lateral, third and fourth ventricles It escapes from the ventricular system of the brain through three foramina (magendie & luschka) in the roof of the fourth ventricle and enters the subarachnoid space It circulates both upward to the surfaces of cerebral hemispheres and downward around the spinal cord Spinal subarachnoid space extends down till the second sacral vertebra اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid CSF provides a fluid medium in which the brain floats and is protected from trauma It is found in the ventricles of the brain and subarachnoid space around the brain and spinal cord It removes waste products associated with neuronal activity Its volume is about 150 ml اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid It possesses inorganic salts similar to those in the blood plasma CSF is an ideal physiologic substrate and thus plays an active role in brain tissue nourishment The pressure of CSF is kept constant and may be raised by straining, coughing and by compressing internal jugular vein in the neck اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid Production CSF is produced continuously at a rate of about 0.5 ml per minute The production of CSF is not pressure regulated It continues to be produced even if the reabsorption mechanisms are obstructed اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid Circulation CSF passes from the lateral ventricles into the third ventricle through the interventricular foramina It then passes into the fourth ventricle through the narrow cerebral aqueduct From the fourth ventricle the fluid passes slowly through the median aperture foramen (magendie) and lateral foramina (luschka) to enter the subarachnoid space It moves superiorly over the lateral aspect of each cerebral hemisphere اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid Circulation Some CSF is moved inferiorly in the subarachnoid space around the spinal cord and cauda equina At the dead end the fluid circulation relies on the pulsations of spinal arteries and movements of the vertebral column CSF not only bathes the ependymal and pial surfaces of the brain and spinal cord but also penetrates the nervous tissue along the blood vessels اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid Absorption The main sites for absorption of CSF are the arachnoid villi that project into the dural venous sinuses especially the arachnoid granules of the superior sagittal sinus The arachnoid granulations increase in number and size with age and tend to become calcified with advanced age اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

Cerebrospinal Fluid Absorption The arachnoid villi serve as a valves If venous pressure rise and exceed the CSF pressure, compression of the tips of the villi closes the tubules and prevents the reflux of blood into the subarachnoid space اسم ورقم المقرر – Course Name and No. 6/27/2019

اسم ورقم المقرر – Course Name and No. 6/27/2019

THE END