Control Lecture 3: The Meninges and The Ventricles Flashcards
What are the three layers of the meningeal layers around the CNS?
- The Dura - Tough, fibrous membrane
- The Arachnid - Soft translucent membrane
- The Pia - Microscopically thin, delicate membrane
Tightly adhered to the surface of the spinal cord
What are the 2 layers of dura?
The dura matter is the first layer. It is formed of 2 layers in the cranium:
- The Periosteal dura - it is tightly adhered to the surface of the skull. There is no space between them - The Meningeal Layer - it is tightly adhered to the surface of the arachnoid matter. There should be no space between them.
The dura matter of the spinal cord is only composed of the meningeal layer, there is no periosteal layer.
Give the 3 dural folds.
The inner Dural layer is separated from the outer layer to protrude into the cranial cavity. This is only a specific areas, here we will have double dura layers. The Dural folds have names.
The folds include:
- Falx cerebi - between the two cerebral hemispheres. It forms a sickle shape from front to back. Some of the attachments is the crista gali of the ethmoid bone. The inferior occipital foreman is the posterior attachment.
- Tentorium cerebelli - Dural fold that separates the cerebral hemispheres from the cerebellum. It forms a tent of the cerebellum.
- Falx cerebelli - this is a tiny Dural fold that cerebrates the two sides of the cerebellum
What is the function of CSF?
CSF provides buoyancy to these structures and acts as a shock absorber. It also acts as a medium for removal of waste and transport of nutrients.
Give the dural venous sinuses.
The dural folds give us venous sinuses (channels). In those channels venous blood from the brain can travel here. CSF can be reabsorbed by entering these channels.
The main sinuses are:
- The Saggital Straight Sinus
- The Confluence of Sinuses
- Sigmoid Sinus
- Cavernous Sinus
- Transverse Sinuses
Which of the following spaces are real or potential in the cranium and the spinal cord:
(a) Epidural Space
(b) Subdural Space
(c) Subarachnoid Space
Cranium
(a) Potential
(b) Potenital
(c) Real - filled with CSF
Spinal Cord
(a) Real filled with fat
(b) Potential Space
(c) Real - filled with CSF
What is CSF?
CSF - Cerebral Spinal fluid is a filtrate from blood but does not contain all try proteins in blood. It is produced from the ventricular system and fills the subarachnoid space. It is produced in the chorioid plexus of the ventricular system am and provides physical protection and chemical stability for the CNS.
What are the divisions of the Ventricular system and the embryonic space that gave rise to them?
The embryonic tube has a fluid filled lumen. In the adult brain a fluid filled space remains.
The Telencephalon space give rise to the lateral ventricle paired. As it grows it grows at a much faster rate than the rest of the neural tube and so folds over the developing diencephalon and adopts a characteristic C shape. This is why may structures in the brain are C shaped including the laterally ventricles of the brain.
The fluid filled cavity in the diencephalon will give rise to the 3rd ventricle. The mesencephalon this will give rise to the cerebral aqueduct. The metencephalon and myelencephalon, which give rise to the pons etc, give rise to the fourth ventricle and the central canal.
How does CSF flow through the ventricular system?
CSF flows through the lateral Ventricle into the third ventricle via the intraventricular foramina (Foramina of Monroe).
It then flows to the third ventricle to the fourth ventricle, together with the CSF formed in the 4th ventricle via the Cerebral aqueduct.
It is then reabsorbed at the Lateral apertures (Foramina of Lusaka) and Median aperture (Foramen of Magendie) into the subarachnoid space.
It is reabsorbed into the venous system using arachnoid villi. These are projections from the arachnoid that pierce into the sinuses that surround the brain. More specifically the superior sagittal sinus.
What are the cisterns of the subarachnoid space?
Wider areas of subarachnoid space are called Cisterns. They are all over the place. They are named according to the region of the brain and spinal cord we find them.
What is the function of the lumbar cistern?
The lumbar system is one cistern in the very bottom of the spinal cord after it has ended. It is an extended area of CSF. It is the preferred site for sampling CSF. The spinal cord ends before the Dural sac ends. We puncture below to prevent damage to the spinal cord.
How does CSF travel through the ventricular system?
Superficial veins to the Superior Saggital Sinus and into the Confluence of Sinuses. It can also enter the confluence of sinuses by travelling from deep veins into the internal cerebral veins, into they great vein and into the straight sinus. From the confluence of sinuses it travels to the transverse sinuses to the sigmoid sinuses and into the IJV.
What are the Denticulate Ligaments?
Denticulate ligaments are projections from the pia. They go attach the spinal cord on either side to the arachnoid matter, and to the dura matter. They are interspersed between the spinal nerves. The denticulate ligaments are bilateral triangular lateral extensions of pia mater that anchor the spinal cord to the dura mater.
