Meninges of the brain. Circulation of CSF. Neural pathways.

To which structures is falx cerebri attached?

- Crista galli ossis ethmoidalis (in front) - Sulcus sinus sagittalis (upper convex margin, contains sinus sagittalis superior) - Protuberanta occipitalis interna (posterior end) The inferior concave margin is free and contains sinus sagittalis inferior)

Where is sinus transversus? In which sinuses it empties?

- Paired - Lies along the posterior margin of tentorium cerebelli in sulcus sinus transversi. It starts at the confluence sinus & continues laterally and anteriorly and empties into sinus sigmoidei which in turn carries the blood to the jugular bulb and further to the internal jugular vein.

Sinus sigmoidei

- Paired sinus - Lies along sulcus sinus sigmoidei. It reaches the jugular bulb and drain into internal jugular vein. (The internal jugular vein collect blood from the brain and superficial parts of the face and neck)

Sinus cavernosi

- Paired sinus - It also known as the parasellary sinus. It lies along sulcus caroticus on either side of sella turcica. - It is the only one of the paired dural venous sinuses that communicates with each other via an anterior and a posterior intercavernous branch that arches over the diaphragma sellae of the pituitary gland which are known as the intercavernous sinuses They are of great clinical importance because of their connections and structures that pass through them. Structures passing through each cavernous sinus are: 1. Internal carotid artery 2. Abducent nerve Structure in the lateral wall of each cavernous sinus are (from sup to inf): 1. III 2. IV 3. V1 4. V2

What is the function of CSF?

- Provide protective cushion around CNS - Mechanical protection - Regulation of intracranial pressure - Metabolic function Carries nutrients to and waste products away from the brain.

Sinus sagittalis superior

- The principle sinus - Unpaired - Lies in sulcus sinus sagittalis superioris and sits superficially in falx cerebri along its upper margin from crista galli to protuberantia occipitalis interna to confluens sinuum (aka torcula) - The small pits (lateral expansions) on either side the sinus are called lateral lacunae in which the arachnoid granulations are located.

Sinus rectus

- Unpaired - Also called tentorial sinus - Lies between falx cerebri & tentorium cerebelli. Lies along the superior surface of tentorium cerebelli where falx cerebri forms a junction with the midline of the tentorium cerebelli. - The posterior part of sinus rectus drains into confluens sinuum

Sinus occipitalis

- Unpaired - Lies along the posterior border of falx cerebelli. Extends from the confluence of sinuses (found at the level of protuberantia occipitals interna) and continues to foramen magnum where it splits into 2 parts passing on both sides of it to foramen jugulare. - Sinus occipitalis is the smallest dural venous sinus.

Which 3 meninges surround the brain?

1. Dura mater encephali (outermost) 2. Arachnoidea mater encephali (in the middle) 3. Pia mater encephali (innermost)

Which 4 processes come from dura mater encephali?

1. Falx cerebri 2. Falx cerebelli 3. Tentorium cerebelli 4. Diaphragma sellae

1. Which of the three meninges of the brain form tela choroidea? 2. What is it?

1. Pia mater encephali which lies close to the brain surface and invaginates into the ventricles to form tela choroidea. 2. Tela choroidea is a thin vascularized loose connective tissue portion of pia mater located between the telencephalic hemispheres and the diencephalon. However, the tela choroidea in the lateral ventricles and in the 3rd are made of the 2 leptomeninges (arachnoidea and pia) while in the 4th ventricle it consist only of pia mater as the arachnoidea does not adhere to the surface of the cerebellum but spans the cerebellomedullary cistern. Tela choroidea gives rise to the choroid plexus. It's basically lamina propria of the ependyma and lies directly adherent to it without any tissue in between.

1. What is granulationes arachnoideae? 2. Where in the brain are they located? 3. What is their function?

1. Small protrusions of arachnoidea through the inner layer of dura mater into the dural venous sinuses. 2. Thus, they are located in between the 2 layers of dura mater encephali. Mainly they are present along the superior sagittal sinus. 3. The granulations allows CSF to be reabsorbed by the brains venous blood within the dural venous sinuses. The arachnoidae granulationes are also called arachnoid villi but as humans age arachnoid villi become aggregated into large clumps called arachnoid granulations.

1. Where is the subarachnoid space? 2. What pass through it? 3. Where does it end?

1. The subarachnoid space lies between arachnoidea mater encephali and pia mater encephali. It contains arachnoid trabeculae which are thin fibrous filaments that hold the two layers in place. 2. Cranial nerves, roots of spinal nerves, arteries and veins from the brain and spinal cord 3. The space extends to the end of the spinal arachnoid mater at the level of S2 vertebra.

Where is cisterna ambiens?

It's thin shee-like extensions of the quadrigeminal cistern that extend laterally around the midbrain connecting it to the interpeduncular cistern.

Haemorrhage inducing brain trauma causing build up of blood creates a space (does not exist naturally) between two meningeal layers. Which layers and what is the name of the potential space?

Between dura mater and arachnoidea mater. The space is called spatium subdurale.

Describe the flow of CSF in the brain.

CSF flow from the lateral ventricles through foramen interventriculare (aka foramen of Monro) to the 3rd ventricle. From the 3rd ventricle it reaches the 4th ventricle via the aquaeduct of Sylvius. Through 2 aperturae laterales (aka foramen of Luschka) and apertura mediana (foramen of Magendie) the CSF comes out into the subarachnoid space and basal cisterns. The CSF then travels up to the granulationes arachnoidae and from there into sinus durae matris and eventually returned to the blood stream from where it originated.

What is the composition of CSF?

CSF is mostly composed of: - Water - Ions: Na+, Cl-, HCO3- - Small amount of amino acids, protein & glucose CSF contain no cells!

How is the CSF produced?

CSF is produced by the highly specialized cells of plexus choroideus. These cells produce CSF by filtrating the blood passing in the underlying vessel. When ions escape from the blood, Na+, Cl´and HCO3-, an osmotic pressure is build up drawing water from the blood through the cells and out into the ventricle.

Function of diaphragma sellae?

Diaphragma sellae lies above sella turcica. It has 2 layers: one lines fossa hypophysialis and the other one covers sella turcica. A small central opening (aka diaphragmatic hiatus) transmits infundibulum of the pituitary gland.

To which part of the brain belongs the ventriculus tertius?

Diencephalon

What is cisternae subarachnoidea? What is the reason behind the formation of them?

Dilatations at certain places of spatium subarachnoideum. in which CSF pools and many vessels and nerves exit toward skull foramina. This pooling is a result of the cranial pia mater being tightly attached to every fissure and contour of the brain (creating gaps) while the cranial arachnoid like the dura more loosely envelop just the immediate surface of the brain.

Which of the three meningeal layers are vascularized (contain blood vessels)?

Dura mater encephali and pia mater encephali. (Arachnoidea is avascular and does not receive any innervation)

Where in the brain is plexus choroideus located?

In the ventricles of the brain: - In the lateral ventricles (except the anterior and posterior horn) - In the 3rd ventricle (in the roof) - In the 4th ventricle (vellum medullare inferius)

Which cistern is the quadrigeminal cistern?

It is cisterna v. magnae cerebri (aka ambient cistern). The space between splenium and superior surface of cerebellum. - It contains the great cerebral vein.

What is the function of spatium subarachnoideum?

It provides a pathway for CSF circulation and absorption around the brain and spinal cord.

Where is arachnoidea mater encephali?

It's a delicate impermeable avascular membrane enveloping the brain loosely. It lies under dura mater and above the pia mater.

Where is falx cerebelli? Which sinus does it hold?

It's a small triangular process between the cerebellar hemispheres. It arises from protuberantia occipitals interna goes along crista occipitalis interna to foramen magnum. It is also attached to lower surface of tentorium cerebelli. It holds sinus occipitalis.

Where is cisterna magna located?

It's between medulla oblongata and inferior surface of cerebellum.

To which part of the brain belongs ventriculus quartus?

Rhombencephalon

Sinus sagittalis inferior

Runs along the lower border of falx cerebri and ends in sinus rectus.

In which sinus occurs the main drainage from within the skull?

Sinus sigmoidei

Which 2 dural venous sinuses are located in fissure longitudinalis cerebri?

Superior and inferior sagittal sinus

To which part of the brain belongs ventriculus lateralis?

Telencephalon

Which sinuses are formed by tentorium cerebelli?

Tentorium lies in the horizontal plane attached posteriorly to sulcus sinus transverse of the occipital bone and thus forming sinus transversus. Anteriorly it extends to margo superior partis petrosae and forms sinus petrosus superior.

What is confluens sinuum?

The connection point of tributary sinuses: 1. Sinus sagittalis superior 2. Sinus rectus 3. Sinus occipitalis This dilated region is drained by the left and right transverse sinuses.

What is the function of sinus durae matris (dural venous sinuses)

The dural venous sinuses are valveless venous channels located between the two layers of dura mater. The functions is to drain deoxygenated blood via bridging veins from the brain and cranial bones, and channel it to the inter jugular vein. The sinuses allow a bidirectional blood flow.

Where is cisterna pericallosa?

The space above corpus callosum (immediatley adjacent to the full length of corpus callosum)

Where is cisterna interpeduncularis?

The space between pedunculi cerebri.

Where is cisterna fossae lateralis cerebri?

The space formed at the anterior part of the temporal lobe where the arachnoid bridges over sulcus lateralis

Where is cisterna chiasmatica?

The space in front of chiasma opticum

How many cisterna subarachnoidea are there?

There are 7 of them: 1. Cisterna cerebellomedullaris (aka cisterna magna) 2. Cisterna interpeduncularis 3. Cisterna chiasmatica 4. Cisterna pericallosa 5. Cisterna v. magnae cerebri (aka quadrigeminal cistern) 6. Cisterna ambiens 7. Cisterna fossae lateralis cerebri

Dura mater encephali

Tough layer of connective tissue which lies closely to the bone of the skull. Dura serves as an internal periosteum (bindvävshinna, som innehåller nerver, blodkärl och lymfkärl) It consist of 2 layers closely connected except at certain places where it forms sinuses for venous blood: 1. Inner meningeal layer 2. Outer endosteal (periosteal) layer