Meninges and CSF

where do you find pia mater? what is it structural features and characteristics?

- Located over the brain and spinal cord - Cannot be seen by eye, is only a few cells thick and gives the brain its shiny appearance. - Is highly vascularized - Adheres to the surface of the brain and enters the gyri and sulci - A sheath of pia accompanies blood vessels as they enter the substance of the brain, called a pial sheath.

where is the location of subarachnoid space? and what does it contain?

- Real space between the arachnoid and pia that contains CSF, arteries and veins. - A supporting network of arachnoid trabeculae hold the brain in the CSF filles subarachnoid space.

What is arachnoid villi - granulations?

Arachnoid villi or granulations are small projections of the arachnoid barrier layer into the venous sinus and its major tributaries. They are closely related to the absorption of CSF.

why does the organs of CNS need protection?

Because all organs of CNS are extremely delicate.

What are the dural partitions/septations? which four can you name?

The dural partitions project into the cranial cavity and partially subdivide the cranial cavity. They include the falx cerebri,tentorium cerebelli, falx cerebelli, and diaphragma sellae.

What does the two layers of dura mater separate from each other at numerous location to form?

The two layers of dura separate from each other at numerous locations to form two unique types of structures. - Dural partitions, which project inward and incompletely separates parts of the brain - Intracranial venous structures.

What are dura maters special features?

- External protective layer - Intracranial folds/septations: creates septations inside the cranium, which creates something of a framework or a scaffold for the encephalon. - Dura mater contains spaces filled by venous blood, called Venous sinuses and are important not only to drain and distribute the blood coming from various places, but also for the reabsorption of CSF.

What does the meningeal layer of dura mater have close contact with? and what is it continues with?

- The inner meningeal layer is in close contact with the arachnoid mater and is continues with the spinal dura mater through the foramen magnum.

what does the periosteal layer of dura mater attaches to? what does it contain? and what is it continuous with?

- The outer periosteal layer: firmly attached to the skull, is the periosteum of the cranial cavity. Contains the meningeal arteries, and is continuous with periosteum on the outer surface of the skull at the foramen magnum and other intracranial foramina.

which intracranial protective layer do we have?

- Under the cranial bones there are meninges: dura mater, arachnoid mater, pia mater. (covering and protecting the CNS) - The meninges protect the encephalon as well as the spinal cord.

Explain the circulation and reabsorption of CSF

CSF circulates within the ventricular system and then it leaves the ventricular to enter the subarachnoid space. It then descends into the vertebral canal to circulate over and around the spinal cord. Some of the CSF may flow all the way down to the caudal portions of the spinal cord. Some may in fact ascend within the subarachnoid space around the cerebral hemispheres until they reach the midline. The CSF is reabsorbed in the midline, it is transferred from the subarachnoid space into the venous system, specifically into the superior sagittal sinus within the dura mater. How can this happen? From the subarachnoid space to CSF will pass through arachnoid specializations named arachnoid granulations. This granulations extend from the arachnoid into the superior sagittal sinus. And they work as one way valves through which the CSF can exit but cannot come back. On the basis of the process, we can confidentially say that the CSF is produced in the ventricles. It circulates through the ventricles, it passes through the subarachnoid space where it circulates, and then it is reabsorbed or taken away by the venous system.

how does the pia mater look like?

Gelatinous consistency as seen in this picture.

where do you find subdural space?

Is more of a virtual space between dura and arachnoid. What this means is that the space is not at all apparent unless there´s something filling it or enlarge it. The subdural space (or subdural cavity) is a potential space that can be opened by the separation of the arachnoid mater from the dura mater as the result of trauma, pathologic process, or the absence of cerebrospinal fluid as seen in a cadaver. - Specifically venous blood creating a large blood clot that fills in and enlarges the space in this case, subdural space between dura and arachnoid as seen underneath in the illustration.

explain this picture:

Position of arachnoid granulations and their interrelationship with the subarachnoid and visual spaces for CSF reabsorption is illustrated here.

What does the dura mater contains? what does the arachnoid contains? what is the fluid named that circulates within the arachnoid layer?

The Dura mater contains large Venous Sinuses. The Arachnoid contains fluid which circulates within the Cranium and within the Vertebral Column. This fluid is named the Cerebrospinal Fluid (CSF) and it originates within the Encephalon, in spaces named the Ventricular System.

What are meninges? what are the three types of meninges?

The brain, as well as the spinal cord, is surrounded by three layers of membranes = meninges. - Dura mater: though outer layer, dense, most external, under the bone - Arachnoid mater: delicate, middle layer Pia mater:inner firmly attached to the surface of the brain. The cranial meninges are continues with, and similar to, the spinal meninges through the foramen magnum, with one important distinction . the cranial dura mater consists of two layers, and only one of these is continues through the foramen magnum.

Where is the epidural space? and what does it contain?

The epidural space is the area between the dura mater (a membrane) and the vertebral wall. - containing fat and small blood vessels The space is located just outside the dural sac which surrounds the nerve roots and is filled with cerebrospinal fluid. The notion of a epidural space filled by a pathological lesion

Where is Falx cerebelli?

The falx cerebelli (Fig. 8.32) is a small midline projection of meningeal dura mater in the posterior cranial fossa. It is attached posteriorly to the internal occipital crest of the occipital bone and superiorly to the tentorium cerebelli. Its anterior edge is free and is between the two cerebellar hemispheres. Another vertical sheath exist between the two cerebellar hemispheres -falx cerebelli

where do you find falx cerebri?

The falx cerebri is a crescent-shaped downward projection of meningeal dura mater from the dura lining the calva that passes between the two cerebral hemispheres. It is attached anteriorly to the crista Galli of the ethmoid bones and frontal crest of the frontal bone. Posteriorly it is attached to and blends with the tentorium Cerebelli. A vertical sheath of dura extends between the two cerebral hemispheres in the great longitudinal fissure - falx cerebri. (den siste røde til høyre nede er ikke falx cerebri)

Where is diaphragm sell located?

The final dural projection is the diaphragma sellae (Fig. 8.32).This small horizontalshelf of meningeal dura mater covers the hypophyseal (pituitary gland) fossa in the sella turcica of the sphenoid bone. There is an opening in the center of the diaphragma sellae through which passes the infundibu- lum, connecting the pituitary gland with the base of the brain, and any accompanying blood vessels.

explain this picture.

The relationship described above are seen here and there are slightly different midline perspective. The lateral ventricle within the right cerebral hemisphere is visible by transparent. The third ventricle, aqueduct, 4th ventricle and central canal are represented and labeled.

Where is tentorium cerebelli located? where is it attached?

The tentorium cerebelli (Fig. 8.32) is a horizontal projection of the meningeal dura mater that covers and separates the cerebellum in the posterior cranial fossa from the posterior parts of the cerebral hemispheres. attached posteriorly: occipital bone along the grooves for the transverse sinuses. laterally: superior border of the petrous part of the temporal bone anteirorly: anterior and posterior crinoid processes. A horizontal sheath extends inwards from the occipitotemporal region and divides the cerebral hemispheres from the cerebellum - tentorium cerebelli.

What is the ventricular system and what is it function?

The ventricular system is the interconnecting network of fluid-filled cavities within the brain, comprising two lateral ventricles, the third ventricle and the fourth ventricle. The ventricles contain cerebrospinal fluid (CSF), which is produced by the choroid plexus within the ventricles. The ventricular system consists of four ventricles in the brain. Ventricles are a communicating network of chambers filled with cerebrospinal fluid (CSF). The ventricular system is the pathway for the CSF and is critical to the central nervous system's overall functioning and development.

what are the 3 different meningeal spaces?

These are several spaces either above or beneath the three layers of meninges: - Epidural space - Subdural space - Subarachnoid space

Explain the ventricular system. where is the lateral ventricles located within? what does the lateral ventricles open into? what are the openings that allows for communication between lateral and 3rd ventricles? what does the 3rd ventricle communicates with further?

Two lateral ventricles: right and left. The lateral ventricles are spaces located within the cerebral hemispheres. Each lateral ventricle is divisible into an anterior horn, body, atrium, inferior horn and posterior horn. The lateral ventricles open into the third ventricle, which is narrow and located in the middle line. This communication between lateral and 3rd ventricles is possible through a couple of opening right and left, named the interventricular foramina. The third ventricle is in the middle line and closely associated with the diencephalon, specifically with the thalamus and hypothalamus. It also communicates with a fourth ventricle by means of a very narrow opening called the aqueduct. Both aqueduct and 4th ventricle are associated with the brainstem. It also has several openings in communication with the subarachnoid space. There you find CSF field space outside the ventricular system. In addition, the 4th ventricle is continues with an extremely narrow opening within the spinal cord named the central canal.

What are the functions of the meninges? TEST: what is the orientation of the meninges?

What are the functions of the meninges? - Protect CNS - To form a supporting framework for the CNS - To create a supporting scaffold for veins and venous sinuses - To form a supporting framework for arteries and nerves. - To enclose a fluid fillet space. The meninges orientation: from external to internal - Dura mater: (under the bones) - Arachnoid: (under the dura mater) - Pia mater: (under the arachnoid and adherent to CNS tissue)

What does tentorium cerebelli leaves a opening for?

While the tentorium cerebelli covers and hides part of the cerebellum in the pursuit of fossil. It leaves an opening for the passage of the brain stem. This opening or gap is named tentorial Hiatus/notch. Which is demarcated here by the tentorial edge or free edge of the tentorium indicated by the yellow arrows.

Who produces CSF?

choroid plexus. Choroid plexus are a secretory tissue responsible for producing CSF in the vertebrate brain.

imaging this: a blood clot occupying space between bone and dura. what would we call this location between the two tissues?

epidural space

What is the spinal cord and encephalon protected by? what is additional protection for these?

protected by the vertebrae and the encephalon is protected by the cranium. Both Vertebral Column and Cranium are made of bone, which is rigid. In addition to this bone shield, there are three additional protective layers formed by membranes named Meninges.

What is the function of CSF?

the CSF has hydraulic as well as immunological functions. - laboratory examination of CSF can help to diagnose CNS infection. Cerebrospinal fluid acts like a cushion that helps protect your brain and spinal cord from sudden impact or injury. The fluid also removes waste products from the brain and helps your central nervous system work properly. Three main CSF function assist the brain by providing: protection, nourishment, and waste removal.

how would you describe the cranial dura mater? (thin, delicate, though..?) what does it consist of? ((2 layers)

the cranial dura mater is a thick, tough, outer covering of the brain. it consist of an outer periosteal layer (outer layer) and an inner meningeal layer (inner layer)

What is extracranial protective layers for the brain?

the scalp. it is the most superficial and over the bone.

does the pia mater completely surround and adheres to the spinal cord?

yes.

learn this picture:

· Because circulation is a dynamic process, a static illustration such as this can do only so much to portray circulation as a function or as a process. · The arrows is informing us about the direction of this flow, from the place where the CSF is produced to the place where the CSF is reabsorbed.

What are the structural features and characteristics of the arachnoid?

· Located under the dura · Located between the dura mater and pia mater · So called because of numerous web like projections (arachnoid trabeculae) passing between the arachnoid and the pia · Is considerably thinner than the dura, thicker than pia · Is avascular (no blood vessels) and although it touches the dura mater it is not attached but is held there by pressure of CSF which it contains · It surrounds the encephalon and spinal cord additional: - Closely follows the contours of the brain - Contains CSF Arachnoid villi (granulations) project into the Dural venous sinuses and act as a route for CSF to be reabsorbed

Explain this picture.

· On this picture you can see how dura mater forms a thick membranous framework for the vein coming form the brain to open into and to have venous blood taken away by the venous sinuses. · The sinuses communicate with each other and are located inside the dura mater. · Superior sagittal sinus. The Dura mater contains large Venous Sinuses.

What is Arachnoid trabeculae?

· So called because of numerous web like projections (arachnoid trabeculae) passing between the arachnoid and the pia mater. A additional special feature of the arachnoid are the so-called trabeculated. These are delicate extensions of arachnoid, found between the arachnoid proper and the peer, as shown in the right. thin strands of connective tissue that extend from the arachnoid mater to the pia mater and help to keep the brain suspended in place.