It is protective coverings (membranes) over the surface of the brain and spinal cord.

1. The Meninges of the Brain • It is protective coverings (membranes) over the surface of • the brain and spinal cord. • The brain is surrounded by 3 membranes, from inside • outwards they are: • 1. Pia mater. • 2. Arachnoid mater. • 3. Dura mater.

4. I. The Pia Mater ►It is a vascular membrane forming the inner most covering membrane of the brain. ► The choroid plexus of the lateral and third ventricles are formed by invagination of th pia mater. ► It send sheaths around the cranial nerves in the cranial cavity.

6. II. The Arachnoid Mater ► It is a thin membrane lying outside the pia mater. ► It send sheaths around the cranial nerves till their points of exit from the skull. ► It is consist of arachnoid villi (microscopic) and arachnoid granulations (macroscopic). ► It is separated from the pia mater by a narrow space called subarachnoid space containing CSF.

8. III. The Dura Mater • ►It is a thick membrane forming the outermost • covering of the brain. • ►It consist of two layer: • 1. Outer or endosteal layer: lines the inner surface • of the skull bones. • 2. Inner or meningeal layer. • ►Surrounds and protects the brain. • ►The two layers of the dura are fused together except • in certain places where they separate to form • venous sinuses.

10. The Intracranial Spaces 1. Epidural space:it is located between the two layers of the dura mater. 2. Subdural space:it is located between the dura mater and arachnoid mater. It contains a small amount of serous fluid. 3. Subarachnoid space:it is located between the arachnoid and pia mater. It contains CSF and blood vessels.

12. Dural Nerves Supply • Trigeminal nerve: • a. Ophthalmic nerve: supplies the dura mater of • anterior cranial fossa. • b. Maxillary and Mandibular nerves: supply the • dura matter of middle cranial fossa. • 2. Vagus and Glossopharyngeal nerves: supply the • dura matter of middle cranial fossa. • 3. The first three cervical spinal nerves. • 4. Sympathetic trunk.

13. Headaches due to Diseases of the Teeth, Paranasal Sinuses, and Eyes Dental infection and sinusitis are common causes of headache. The pain is referred to the skin of the face and head along the branches of the trigeminal nerve.

15. The Cerebro-Spinal Fluid Definition: it is the fluid which circulates in the ventricles and central canals of the CNS and also fills the subarachnoid space. Production of the CSF: It is secreted by the choroid plexuses of lateral, third and fourth ventricles.

16. Circulation of the Cerebro-Spinal Fluid The CSF in each lateral ventricle → interventricular foramen of Monro → third ventricle → aqueduct of midbrain → fourth ventricle → some fluid enter the central canal of spinal cord but the majority passes through the 3 foramina (one median of foramen Magendie & two lateral foramins of Lushka) → subarachnoid space were it flows over the surface of the brain and spinal cord.

18. Absorption of the Cerebro-Spinal Fluid The CSF is absorbed by means of arachnoid villi and arachnoid granulations which absorbs the CSF from the subarachnoid space into the dural venous sinuses to reach the blood stream.

20. Functions of the Cerebro-Spinal Fluid 1. Cushions and protects the central nervous system from trauma. 2. It takes the place of the lymph in the CNS which is devoid of lymphatic vessels. 3. Regulation of the intracranial pressure. 4. Removes metabolites and toxics from the central nervous system. 5. Nourishes the central nervous system.

21. Characters of the Normal Cerebro-Spinal Fluid Appearance: clear watery fluid, isotonic. Amount:100- 150 cc. Replacement: it continuously produced and absorbed at a rate of 400-500 cc daily (it is replaced 3 times per day). Pressure: 100-180 mm. of water. Rate of production: 0,3-0,4 ml/min. Cells: 0-5 WBCs per cubic millimeter. Glucose: 60 mg/dl (70% of serum glucose). Total protein: 15-50 mg/dl.

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