Lecture 4

Question 1

meninges

Answer 1

three membraneous layers that surround the brain & SC

Question 2

dura mater

Answer 2

• outermost layer directly under the skull
• tough and flexible
• protects brain from displacement
• two layers :
  1.outer postereal layer - fibrous
  2.inner meningeal layer - smooth

Question 3

arachnoid mater

Answer 3

• middle layer
• lies closely against dura mater
• in some places, shows small protrusions into dura mater called arachnoid granulations/villi
• they transfer CSF from ventricles back into bloodstream

Question 4

pia mater

Answer 4

• innermost layer
• projects into ventricles and fuses with ependyma

Question 5

ependyma

Answer 5

• membraneous lining at the ventricles
• form structures called the choroid plexi that produce CSF

Question 6

epidural space

Answer 6

potential space b/w the dura mater of the SC and the vertebral canal wall

Question 7

subdural space

Answer 7

potential space b/w the dura mater and arachnoid mater

Question 8

subarachnoid space

Answer 8

• real space b/w arachnoid mater & pia mater
• filled with CSF
• all blood vessels entering brain & cranial nerves pass through

Question 9

fibrous septa

Answer 9

seperates the two dural layers

Question 10

CSF

Answer 10

• clear, plasma like fluid produced within spaces called ventricles
• found in subarachnoid space
• central canal wall contains CSF
• functions :
  1. functions as a cushion for neurons
  2. brings nutrients to brain & SC
  3. removes waste from system

Question 11

CSF circulation pathway

Answer 11

1. CSf passes from lateral ventricles to 3rd ventricle via intraventricular foramen
2. from 3rd ventricle to 4th ventricle via cerebral aqueduct
3. from 4th ventricle passes through medial & lateral apertures
4. CSF flows through subarachnoid space of brain & SC
5. finally reabsorbed into dural venous sinus through arachnoid granulations/villi

Question 12

skull

Answer 12

• cranial cavity is rigid box with brain, blood vessels and CSF
• communicates with verterbal canal wall through foramen magnum and with tissues outside the cranium via foramina

Question 13

intercranial pressure

Answer 13

because it is a rigid box, extensive bleeding or a tumour inside the cranium has little room for expansion and will lead to intercranial pressure

Question 14

blood brain barrier

Answer 14

structures formed due to establishments of tight junctions b/w endothelial cells

Question 15

purpose of BBB

Answer 15

• protect against circulating toxins or pathogens that could cause infections
• allows vital nutrients to reach brain
• helps maintain relatively constant levels of hormones nutrients & water in brain

Question 16

circumventricular organs

Answer 16

• gaps in BBB
• not protected by BBB
• examples - pituary gland, pineal gland, subfornical organ

Question 17

problem with BBB?

Answer 17

• in an infection in the brain, BBB makes delivery of antimicrobial agents to the brian very difficult
• can be too restrictive

Question 18

Meningococcal disease

Answer 18

• meningococcal bacteria can bind to endothelial wall
• causes tight junctions to open slightly
• BBB becomes porous allowing bacteria and toxins to infect brain tissue
• leads to inflammation & sometimes death

Question 19

endothelial cells

Answer 19

• line interior of all blood vessels
• wedged together closely to form tight junctions
• these allow small, fat soluble molecules to pass through the capillary wall and into brain tissue
• large molecules gain entry through transporter proteins