Meninges, Ventricles, and CSF Flashcards
What are the three meningeal layers?
Dura
Arachnoid
Pia
What is the cranial dura?
Composed of two layers - outer most essentially serves as periosteum and is not continuous with the the dura of the spinal cord
Inner layer is fused with the endosteal layer except where it forms the septa
What is the function of the dural septa?
Provide support and protection for the brain
Protects the brain against sudden and violent movements of the head
What is the Falx Cerebri?
Longitudinal Septum in the sagittal fissure between the two cerebral hemispheres
What is the tentorium cerebelli?
Septum that extends horizontally between the occipital lobes and the cerebellum attached to the falx cerebri
Forms roof over the posterior cranial fossa
Between what layers are the dural venous sinuses located?
Between endosteal and meningeal layers or between two meningeal layers
Where is the superior sagittal sinus?
Within the attached borders of the falx cerebri
Receives branches from the superior cerebral veins
Major area where CSF return to the general systemic circulation
Where is the inferior sagittal sinus?
Extends along the inferior free margin of the falx cerebri
What is the Great Cerebral Vein of Galen?
Collects venous blood from internal cerebral veins, joins the inferior sagittal sinus to form the straight sinus
What lies within the subarachnoid space?
Trabeculae (fibrous filaments) that bridge the arachnoid and pial membranes
CSF
All major blood vessels of the brain
Where is the cerebellomedullary cistern?
Spans the space over the cerebellum and the part of the brainstem called the medulla
Where is the pontine cistern?
Lies over the pons
Where is the interpeduncular cistern?
Lies over the interpeduncular fossa (ventral brain surface)
Circle of willis lies within this cistern
Where is the lumbar cistern?
Extends from vertebral levels L1/L2 to S2
Area where spinal taps are done
What are arachnoid villi?
Structures which allow for passage of CSF from the subarachnoid space into the superior sagittal sinus back to the general circulation
What is the pia mater?
thin, highly vascularized membran that adhers closely to the surface of the brain and spinal cord
What are Virchow-Robin spaces?
Subarachnoid space around anastomosing vessels within the brain before the major branches pass into the brain substance
What is papilledema?
Edema of the optic papilla caused by elevated CSF pressure around the optic nerve
Describe the lateral ventricles.
The two larges ventricles, one in each hemisphere
Each ventricle has extensions called horns, named after the lobes or direction they extend
What connects the lateral ventricles and the third ventricles?
Intraventricular foramen of Monro
What forms the walls of the third ventricle?
Thalamus and Hypothalamus
What connects the third and fourth ventricles?
Aqueduct of sylvius
What structures form the fourth ventricle?
The roof is formed by the cerebellum and its floor by the pons and medulla
How does CSF enter the subarachnoid space from the 4th ventricle?
Through two lateral foramina of Luschka
And a medial foramen of Magendie
What is the function and location of the Pineal Body?
Outside the BBB
Secretes melatonin, important for circadian rhythms
What is the function of the Organum vasculosum of the lamina terminalis?
Sensory area that supplies input to other brain regions
Contains osmoreceptors sensitive to Na and osmotic pressure in blood
What is the function of the median eminence of the hypothalamus?
Secretes hormones
CRF, TRH, GnRH, GHRH
What is the function of the subcommissural organ?
Produces transthyretin
What is the function of the neurohypophysis?
Endocrine organ
Produces oxytocin, vasopressin
What is the function of the Area Postrema?
Chemoreceptor trigger zone (vomit center)
Where is CSF found?
Ventricles, Subarachnoid space and cisterns
Interstitial space in the brain
Continuously produced, but only a small amount of CSF is in the ventricles at any one time
What does pink or red CSF indicate?
Blood in the CSF
Most commonly due to leakage/rupture of an aneurysm in CoW
What does yellow and spontaneous clotting CSF indicate?
Increased protein content or from lysis of RBC
Increased IgG can indicate a chronic inflammatory process within the CSF
What does cloudy or white CSF indicate?
Bacterial meningitis
Elevated WBCs
What does clear to slightly cloudy CSF indicate?
May indicate aseptic meningitis
Elevated WBCs
Commonly associated with a viral infection
What causes the circulation of the CSF?
Arterial pulsations
Respiratory movements
Vasomotor activity
All move towards the superior sagittal sinus
