The Ventricular System & Circulation of CSF

Question 1

Ventricles:
- are
- derived from
- purpose

Answer 1

• small cavity/chamber
• derived from the expansion and
  folding of the neural plate
• to produce and distribute CSF

Question 2

Ventricles Embryology:

Answer 2

Question 3

The neural tube is formed as it

Answer 3

detaches from the epiblast = neurulation

The neural crest cells seal the remaining space at the cranial and caudal ends are called the neuropores

If the pores do not seal causes congenital abnormalities

Question 4

What cells develop into the PNS?
What cells develop into the CNS?

Answer 4

• neural crest cells detach and create
  the PNS
• the neural tube creates the CNS

Question 5

Formation of Brain Vesicles:

Answer 5

neural tube starts to expand into three balloons at the top (prosencephalon, mesencephalon and rhombencephalon)

the three balloons then develop into 5 different components, which then fold in on themselves to create the brain

the rest of the tube forms the spinal cord

Question 6

Brain Flexures:

Answer 6

the five different components fold in on themselves: in the brain we have the cerebral hemispheres on top, then the midbrain and then the cerebellum

forms different flexures: midbrain flexures, pontine flexure

(hollow cavity)

Question 7

Lateral ventricles are next to which parts of the brain

Answer 7

telencephalon and prosencephalon

Question 8

Aquaduct is

Answer 8

the ventricular system near midbrain

Question 9

Central Canal:

Answer 9

hole in the middle of the spinal cord

Question 10

Foramen of Monroe are

Answer 10

2 holes that divide the lateral ventricles

INTERVENTRICULAR

Question 11

Foramen of Magendie and Foramen of Luschka

Answer 11

foramina connect the interventricular system so that CSF can leave the sealed structure

Question 12

The Ventricular Pathway:

Answer 12

Question 13

The Ventricular Pathway:

Answer 13

Question 14

Dandy-Walker Malformation:

Answer 14

• developmental problem with
  ventricular system resulting in an
  expanded fourth ventricle

Question 15

Dandy-Walker Malformation:

Answer 15

Question 16

What cells line ventricles?

Answer 16

Choroid cells = specialised ependymal cells
Ependymal cells = specialised glial cells

Question 17

Choroid Cells:
- function

Answer 17

to produce cerebrospinal fluid (CSF)

Question 18

Where does the majority of choroid cells lie?

Answer 18

The lateral ventricles

Question 19

What allows contact of CSF with brain cells?

Answer 19

leaky lining?

Question 20

***Choroid plexus:

Answer 20

network of choroid cells with capillaries

Question 21

Draw choroid plexus:

Answer 21

Question 22

Label diagram on addendum A

Answer 22

Choroid plexus

one confluent tube system

Question 23

Formation of CSF:

Answer 23

insert diagrams

First diagram blue = ventricles
green = ependymal cells

Second diagram shows fenestrated capillaries allowing substances to seep out into the extracellular space

in order for molecules to move from outside of capillaries and into CSf they have to pass through the choroid cells

they can not pass between the choroid cells because the choroid cells have tight junctions

Channels in choroid cells allow substances to pass into CSF.

Choroid cells also contain carbonic anhydrase which breaks down water into CO2 and H2

creates an acid, which can act as a buffer

Question 24

What is the composition of CSF determined by?

Answer 24

the channels the choroid cells possess

Question 25

Drugs that impact the kidneys can impact the brain

Answer 25

because channels found in cells lining kidney are same/similar to those found in choroidal cells

Question 26

CSF Production Cellular Level:

Answer 26

Water is broken down into bicarb which is pushed over by opposite flow of Na+ and K+ Creates fluid

Question 27

Drugs that inhibit carbonic anyhydrase results in

Answer 27

alteration of CSF production (slows down)

Question 28

CSF: - is - looks - how much produced a day? - means - normal CSF pressure - function

Answer 28

- specialised version of blood - clear and colourless - 500ml per day, only need 150ml - rate of production = rate of reabsorption (high turnover results in efficient waste disposal) - 5-18cmH2O - offers mechanical and chemical protection

Question 29

CSF vs Plasma table

Answer 29

Question 30

The Blood Brain Barrier: - function - formed by - areas that lack BBB - hence

Answer 30

- protects the brain from rapid shifts in electrolytes and metabolities - formed by tight junctions - choroid plexus and circumventricular organs (like pineal gland) lack a BBB - circumventricular organs are directly exposed to blood solutes -> neuroendocrine control

Question 31

Blood Brain Barrier:

Answer 31

capillaries inside the brain are unfenestrated three different aspects: - thick basement membrane - tight junctions between cells - astroctyes are a different glial cells which seal off the capillary hence offer a protective mechanism to the brain and are involved in cell signalling

Question 32

CSF Circulation:

Answer 32

CSF circulates in the ventricular system three hollow tubes that allow CSF to travel into meningeal layers between the pia mater and arachnoid mater hence in the sub-arachnoid space fluid bathes brain in the sub-arachnoid space ***arachnoid granulations are outpouchings from the arachnoid layer into the dural layers, allowing waste products to travel into the venous system via the dural venous sinus - The CSF passes from the lateral ventricles to the third ventricle through the interventricular foramen (of Monro). - From the third ventricle, the CSF flows through the cerebral aqueduct (of Sylvius) to the fourth ventricle. - From the fourth ventricle, some CSF flows through a narrow passage called the obex and enters the central canal of the spinal cord. However, the majority of CSF passes through the apertures of the fourth ventricle; the median aperture (of Magendie) and two lateral apertures (of Luschka). Via these openings, the CSF enters the cisterna magna and cerebellopontine cisterns, respectively. - From there, the CSF flows through the subarachnoid space of the brain and spinal cord. - It is finally reabsorbed into the dural venous sinuses through arachnoid granulations.

Question 33

CSF Cisterns and the Venous System:

Answer 33

Question 34

CSF Cistern:

Answer 34

- pools of CSF in larger spaces - eg pre-pontine cistern

Question 35

CSF Venous System: end-point:

Answer 35

All dural venous sinuses drain into the sigmoid sinuses which drain into the internal jugular vein, which combines with the subclavian veins to form the brachiocephalic veins which combine to form the superior vena cava at T4/5

Question 36

Glymphatic System

Answer 36

Arteries in the brain dive down into the brain, penetrating arteries creates a space between the tissue and and the vessels move from periarterial to the perivenous space and then into venous sinuses **occurs through channels called aquaporin 4 channels and through force/connective flow

Question 37

Problems with CSF Circulation:

Answer 37

- higher pressure: - blockage of flow (stenosis, thrombosis) - overproduction (choroid plexus papilloma) - reduced reabsorption (neoplasm) - lower pressure: - leak (trauma/spina tap) causing brain sag

Question 38

Hydrocephalus: insert diagram

Answer 38

- fluid on the brain - two types: - communicating (no problem with the hydrocephalus) - non-communicating = blockage

Question 39

Hydrocephaly on CT:

Answer 39

- fluid expands, squashes brain because brain is sealed - in child head is still moldable as it is growing, lateral ventricles will expand, makes the skull expand = make sure head circumference is correct

Question 40

Treatment of Hydrocephaly:

Answer 40

- drugs that inhibit carbonic anhydrase (not very fast) - surgical intervention = put a tube in ventricles to remove some fluid, add tube down into peritoneum = ventriculo-peritoneal shunt

Question 41

Lumbar Puncture:

Answer 41

- diagnostic tool - into cauda equina (around L3/4/5)

Question 42

CSF Analysis:

Answer 42

Question 43

Environment of the brain and spinal cord is protected by CSF both mechanically and chemically.

Answer 43

bouyancy nutrients

Question 44

Answer 44