ANAT: Meninges & CSF

Question 1

• What are the three connective tissue layers of the meninges, from outside to inside?
  
  • What is the function of each of these layers?
• What is the function of the meninges as a whole?

Answer 1

• Meninges supports brain, spinal cord, and its blood vessels.
• Dura mater (“tough mother”)
  
  • Tough, inelastic, outermost layer.
  • Protects and supports the brain and spinal cord.
  • Follows the bone contours.
• Arachnoid mater (“spider-like”)
  
  • Spider web like layer of fibrils.
  • Contains CSF.
    
    • CSF circulates in subarachnoid space.
  • Avascular.
• Pia mater
  
  • Thin vascular layer for the transmission of blood vessels to the brain.
  • A fine membrane fused to the arachnoid.
  • Follows closely the sulcal indentations on the surface of the brain.

Question 2

• What are the two layers of the dura mater, from outside to inside?
• Usually these two layers stick together. What is the name of the structures that exist when they separate?

Answer 2

• Periosteal layer.
• Meningeal layer.
• Dural folds and sinuses.

Question 3

• What are the three main dural folds?
  
  • What do they separate?
• What’s the fourth?

Answer 3

• Falx cerebri.
  
  • Cerebral hemispheres.
    
    • Lies in the longitudinal cerebral fissure,
• Falx cerebelli.
  
  • Cerebellar hemispheres.
• Tentorum cerebelli.
  
  • Cerebellum and occipital lobes.
  • Divides the cranial cavity into supratentorial and infratentorial compartments.
• Diaphragma sellae.
  
  • Retains the pituitary gland beneath it in the fossa hypophyseos.

Question 4

• Name eight venous sinuses.
  
  • Fill them in on the diagram.

Answer 4

• Superior sagittal.
• Inferior sagittal.
• Transverse.
• Sigmoid.
• Superior petrosal.
• Inferior petrosal.
• Straight.
• Cavernous.

Question 5

• Describe the features of the arachnoid mater.
• How do cisterns form?
• Name eight major cisterns.
• Differentiate between arachnoid villi and granulations.

Answer 5

• The arachnoid mater makes arachnoid villi.
  
  • Small protrusions through the dura mater into the venous sinuses of the brain, which allow CSF to exit the subarachnoid space and enter the blood stream.
    
    • Eg CSF goes from subarachnoid space back into the superior sagittal sinus to re-enter the bloodstream.
• Arachnoid mater and dura mater remain attached and the pia mater follows the brain → formation of subarachnoid cavities (cisterns).
  
  • Cisterns = areas where dura doesn’t follow the brain.

1. Cerebellomedullary cistern (cisternae magna).
2. Pontine.
3. Interpeduncular.
4. Optic chiasm.
5. Lamina terminalis cistern.
6. Superior cistern.
7. Lateral fissure cistern.
8. Lumbar cistern.

• Arachnoid granulations are composed of multiple villi.

Question 6

• Where is CSF produced?
  
  • Where is this structure found?
  • Where is it MAINLY found?
• Describe its circulation.

Answer 6

• The choroid plexus.
  
  • Plexus of blood vessels.
  • Turns CSF over 3-4 times a day.
  • Found in the ventricles and central canal, but mostly in lateral ventricles.
• Travels from the lateral ventricles, through the interventricular foramen, and into the third ventricle. From here is passes through the narrow cerebral aqueduct into the fourth ventricle. It leaves this ventricle via the lateral (x2) and median apertures (x1). The CSF is then resorbed through the arachnoid villi into the superior sagittal sinus, where it can re-enter the bloodstream.