NEUROANATOMY Lecture : 6 The Ventricles and Meninges of the Brain, The Cerebro-Spinal Fluid Prepared and presented by: Dr. Iyad Mousa Hussein, MD, Ph.D in Neurology Head of Neurology Department Nasser Hospital

LECTURE OBJECTIVES: The Ventricles of the Brain. Definition, Site, Communicates, and Parts of the Lateral Ventricle. Definition, Site, Communicates, and Parts of the Third Ventricle. Definition, Site, Communicates. and Parts of the Fourth Ventricle. The Meninges and Intracranial Spaces of the Brain. Dural Nerve Supply. Headaches due to Diseases of the Teeth, Paranasal Sinuses, and Eyes. 9. Definition, Production, Circulation, Absorption, and Functions of the Cerebro-Spinal Fluid. 10. Characters of the normal Cerebro-Spinal Fluid.

The Ventricles of the Brain ► The brain and spinal cord float within a protective bath of cerebrospinal fluid (CSF), which is produced by the choroid plexus within the ventricles of the brain. ► Each part of the CNS contains a component of the ventricular system. ► The ventricles contains about 35 ml of CSF.

The Ventricles of the Brain There are four interconnected ventricles in the brain: 1. Two lateral ventricles (Right and Left). 2. Third ventricle. 3. Fourth ventricle.

The Ventricles of the Brain

The Lateral Ventricle Definition: it is the cavity of the cerebral hemispheres. There are two lateral ventricles (Right & Left), one in each cerebral hemisphere. Site: it is the cavity present in each cerebral hemisphere. Communications: It communicates with the third ventricle through the interventricular foramen of Monro.

Parts of the lateral ventricle 1. The body (central part): lies in the parietal lobe. It communicates with the three horns. 2. Anterior horn (frontal): lies in the frontal lobe. 3. Posterior horn (occipital): lies in the occipital lobe. 4. Inferior horn (temporal): lies in the temporal lobe.

The Third Ventricle Definition: It is a narrow cavity situated in the midline between two thalami. it is the a cavity of the diencephalon. Site: it is lying in the median plane between the right and left thalami.

Communications of the Third Ventricle Anterosuperiorly: on each side, it communicates with each lateral ventricle by an interventricular foramen of Monro. 2. Posteroinferiorly: in the median plane, it communicates with the fourth ventricle through the cerebral aqueduct (of Sylvius), which passes through the midbrain.

Recesses of the third ventricle Optic recess: just in front of the optic chiasma. 2. Infundibular recess: in the infundibulum. 3. Supra-pineal recess: just above the pineal body. 4. Pineal recess: in the pineal body.

Choroid Plexus of the Lateral and Third !!!!!!! Ventricles

The Fourth Ventricle Definition: It is the cavity of the hindbrain (Rhombencephalon). Position: it lies between: 1. The dorsal surfaces of the pons and upper part of the medulla anteriorly. 2. The ventral surface of the cerebellum posteriorly.

Angles of the fourth ventricle Superior angle: where the fourth ventricle is continues with the aqueduct of the midbrain. 2. Inferior angle: where the fourth ventricle is continuous with central canal of the closed medulla. 3. Right & Left lateral angle: each lateral recess opens into the subarachnoid space (by right and left foramen Luschka).

Communications of the Fourth Ventricle 1. cerebral aqueduct (of Sylvius): in the superior median plane (superior angle), it communicates with third ventricle. 2. Central spinal canal: in the inferior median plane (inferior angle). 3. One median foramen (foramen of Magendie): in the lower part of the inferior medullary velum. 4. Two lateral foramens (foramens of Lushka): one in each lateral recess. Through foramens of Magendie and Lushka, the CSF leaves the fourth ventricle to the subarachnoid space.

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.

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.

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.

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.

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.

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 3. The first three cervical spinal nerves. 4. Sympathetic trunk.

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.

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.

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.

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.

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.

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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