CSF

Foramina of Luschka and magendie

-located at the *widest part of the fourth ventricle*, the foramina of Luschka are the paired (2) lateral apertures of the *posterior medullary velum* that allow *CSF* to leave the ventricular system and enter the subarachnoid space -the foramen of Magendie is at the midline between the foramina of Luschka and has the same function (primary portal where CSF produced in the ventricles can enter the subarachnoid space) Note: *hydrocephalus* can occur if these foramina are occluded (i.e. via a meningeal tumor)

CSF flow

1. CSF is secreted by choroid plexus 2. CSF flows through interventricular foramina into third ventricle 3. Choroid plexus in third ventricle adds more CSF 4. CSF flows down cerebral aqueduct to fourth ventricle 5. Choroid plexus in fourth ventricle adds more CSF 6. CSF flows out two lateral aparatures (Luschka) and one medial aperture (magendie) 7. CSF fills subarachnoid space and bathes external surfaces of the brain & spinal cord 8. At arachnoid villi, CSF is reabsorbed into venous blood of dural venous sinuses

Areas that lack BBB

1. Post lobe of pituitary - neurohypophysis 2. Median eminence (in hypothalamus) 3. Vascular organ of lamina terminals (febrile response) 4. Area postrema (chemoreceptor trigger zone for vomiting) 5. Subfornical organ (mediate effects of circulating angiotension-2 on blood pressure, sodium balance 6. Pineal gland 7. Subcommissural organ 8. Choroid plexus

Brain Cisterns

Cisterns are compartments in the subarachnoid space where the pia mater and the arachnoid membrane are not an close contact and the CSF forms pools or cisterns.

Dura vs Leptomeneges

Dura: periosteal (adheres to skull) & menegeal Leptomeneges: arachnoid & pia mater (adheres to the parenchyma of the brain)

Choroid plexus

Produces CSF Choriod plexus goes in the lateral ventricle through the interventricular foramen to the roof of the third ventricle. Passes through the cerebral aqueduct to the 4th ventricle. The choriod plexus gets out through three holes: middle (to the foramen of magendie/ medial aperture) and Foramina of luschka (lateral aperture). Then goes to cisterns magna

Glymphatic system

perivascular pathway that allows CSF to flow through brain tissue. And is a waste clearance system for interstitial solutes. Made of astrocytes and uses BVs. B amyloid is a solute that is filtered out and efflexed into the blood. Accumulation of B amyloid is a component of Alzheimer's diseases.

CSF absorption

The subarachnoid space is perispinal and perimedullary, meaning the CSF flows around the outside of the brain and the spinal cord between the arachnoid and pia mater. Once the CSF is in the subarachnoid space, it circulates around the brainstem and the subarachnoid basal and ambient cisterns. Next, it reaches the external surfaces via the tentorial aperture and is absorbed via arachnoid granulations located in venous lacunae connected to the superior sagittal sinus and, to a lesser extent, directly in the superior sagittal sinus. This sinus eventually drains into the internal jugular vein. However, the majority of drainage from the arachnoid granulations flows into large venous lacunae located in the parasagittal plane, adjacent to the midline superior sagittal sinus.

Formation of choroid plexus

The ventricle is lined by single cell ependyma The pia mater is adhered to the ependyma A BV comes in and creates an indentation (hand like structure) When blood comes in it creates a fissure- choroidal fissures BVs proliferate and the choroidal fissure Follows creating the choriod plexus The ependyma surrounded the fissure is called the choridal epithelium

brain ventricles

cerebrospinal fluid filled cavities within the brain Interventricular foramen connects lateral ventricle to 3rd ventricle 3rd ventricle to cerebral aqueduct to 4th ventricle 4th ventricle is continuous w/ the subarachnoid space surrounding the brain via the foramina magendie and luschka