1. Ventricular System, Meninges, and CSF Study suggestion: Read the selected pages from Chapter 2 first, then read Chapter 8

2. Thinking questions
How to pack something very fragile that has to be shipped cross-country
How to make a person who is heavy into a person who can be lifted with one hand

3. Overview of this lecture, so you see the big picture
CNS is very fragile and vulnerable, and it is constantly being transported around
Cushion from ___________ and ___________
Encase the whole thing in _______________
CNS would collapse under its own weight if placed on a table. Brain’s weight is reduced from 1500g (3.3 lbs)  75 g (1/10 of a lb.) because it is ___________ in __________

4. Introduction to CSF Cerebrospinal Fluid (CSF) Colorless
Continuously produced deep within internal brain spaces called ___________, and cushions around whole CNS ______________
Functions
Mechanical cushion around CNS
Removal of harmful substances & waste

6. CSF CIRCULATION: Where does it start?
Produced in ventricles*, and flows caudally through ventricular system
Two lateral ventricles
Interventricular foramen
One third ventricle
Cerebral aqueduct
One fourth ventricle
Two foramina of Luschka
One foramen of Magendie
* CSF produced by choroid plexus in the ventricular cavities

7. Can you find the structures mentioned in the previous slide on these figures?

8. So, CSF exits the ventricular system
Exits from 4th ventricle through
Two foramina on lateral sides of fourth ventricle
= __________________
One foramen in posterior part of fourth ventricle = foramen of ___________________
Enters into a space called _____________ that encircles/covers whole CNS!

9. More about subarachnoid space
Net-line structure within the SAS is called arachnoid trabeculae
Large pockets/enlargements of SAS are called _______________________
Do you see the arachnoid trabeculae? Do you see any cisterns?
Lumbar puncture (spinal tap) from lumbar cistern

10. Subarachnoid space is sandwiched between two of the three covering layers over the CNS
These three layers are called the MENINGES.
??? How is this related to meningitis?

11. Outer covering of brain: Where are the meninges?
(Scalp)
(Muscles and surface arteries)
(Bone: Skull)
Meninges
Cover brain and spinal cord
3 layers
Between two of the layers is a cushioning layer of fluid called cerebrospinal fluid

12. Meninges Three-layer covering of CNS, from outermost to innermost
Dura mater (outermost, tough, DURable)
has 2 fused, closely united sub-layers
One next to bone
One next to arachnoid mater
2 layers separate in spots to form venous sinuses
Arachnoid mater + subarachnoid space (below it):
Pia mater (innermost, “tender” fragile)
Three layers continuous: brain & spinal cord

13. Meninges cover all of the CNS, including spinal cord

14. Dura mater: More details
In certain places, the two layers separate to form dural venous sinuses (system of cavities and channels to drain venous blood)
Rigid sheets of dura mater extend into cranial vault (Fig in W&A)
Falx cerebri
flat, crescent-shaped
separates two cerebral hemispheres
Tentorium cerebelli
dome-shaped
separates cerebral hemispheres from cerebellum
Diagphragma sella (not pictured)
Roof of structure that encloses pituitary gland

15. Do you see where the dural venous sinuses are?

16. Coronal section: More details on dura mater
Look at falx cerebri and tentorium cerebelli
Folds of dura mater
Brace brain from displacement
Receive blood from brain’s cerebral veins
Receive cerebrospinal fluid from subarachnoid space

18. Subarachnoid space (SAS): More details
Sub-arachnoid space filled with cerebrospinal fluid (CSF)
Extends into sulci (p. 63 of W)
Larger portions of this space called cisterns (Figure 3-9)
Arachnoid protrudes into dural venous sinuses
Protrusions = arachnoid villi
CSF absorbed into blood + removed from SAS

19. Pia mater: More details
Adheres tightly to surface of brain
Outer surface has many blood vessels
Many blood vessels cross the space between the pia and the arachnoid maters

20. Circulation of CSF:
Lateral view

21. Clinical applications related to CSF
Blockage of CSF movement or failure of resorbtion mechanism  accumulation of fluid in ventricles or around brain tissue  hydrocephalus
Treated by shunting CSF from ventricle to body peritoneal
or pleural cavities
Medical diagnostics on CSF
CSF pressure (high pressure associated with tumor, hemorrhage, hydrocephalus, meningitis or encephalitis)
CSF chemical and cell studies

22. Clinical application related to meninges Extracerebral hemorrhages
Hemorrhages from the blood vessels in the meninges or on the surface of the brain, from:
Weakness of vessel wall
Traumatic injury
(rarely)-extreme fluctuations in blood pressure
Types, based on where blood accumulates
Subarachnoid: b/w arachnoid and pia (most common, from
aneurysm
arteriovenous malformation (AVM)
Subdural: under dura (esp. from TBI)
Epidural: b/w dura and skull (esp. from TBI)
After bleeding stops, left with hematoma

23. Clinical application: Extracerebral hemorrhages (cont.)
Types, based on where blood accumulates
Subarachnoid: b/w arachnoid and pia (most common, from
aneurysm
arteriovenous malformation (AVM)
Subdural: under dura (esp. from TBI)
Epidural: b/w dura and skull (esp. from TBI)
After bleeding stops, left with hematoma