Development of the ventricles

Question 1

Describe the development of the ventricles

Answer 1

Around day 24 the lumen of the neural tube becomes ventricles and central canal

Lumen expands at cranial end to form ventricles- there is a ventricle associated with each part of the brain

Ependymal layer lines ventricles and central canal

Question 2

What is the Foramen of Monro?

Answer 2

Also called the interventricular foramen

Lateral ventricles communicate with the third ventricle through it.

Question 3

What is the function of the septum pellucidum?

Answer 3

Seperates the lateral ventricles

Question 4

To what lobes are the different horns associated to?

Answer 4

Anterior horn- frontal lobe
Body- parietal lobe
Inferior horn- temporal lobe
Posterior horn- occipital lobe

Question 5

Describe the appearance and location of the third ventricle

Answer 5

Sits like cleft beltween thalami

Fornix forms roof

Question 6

What is the Cerebral aqueduct?

Answer 6

AKA Aqueduct of Svivius

Communication between the third ventricle and the fourth aqueduct

Surrounded by the midbrain (passes through)

Question 7

Describe the appearance and location of the fourth ventricle

Answer 7

Surrounded by hindbrain:
- Cerebellum posterior
- Pons and medulla anterior
- Cerebellar peduncles lateral
Characteristic rhomboid shape (coronal view)
Continuous with the central canal of the spinal cord and subarachnoid space

Question 8

Descrobe the fourth ventricle communication

Answer 8

Three foramen exit into subararachnoid spaces (specifically into cisterna magna)

2x Formaen of Luschka (lateral)
1x Foramen of Magendie (middle)

Question 9

What is the choroid plexus?

Answer 9

Produces CSF
Filters blood from branches of internal carotid and basilar arteries
Present throughout the ventricles (looks like caviar)

Question 10

Describe the structure of the choroid plexus

Answer 10

Very simple
Campillary network surrounded by cuboidal ep.
During CSF producstion:
1. blood filtered through fenestrated capillaries
2. components transported through cuboidal ep. into ventricles

Tight junctions between ep. cells prevent macromolecules from entering CSF, only permeable to H20 and CO2. They form the blood-CSF barrier.

Question 11

Describe the cupidoidal ep.

Answer 11

Specialized ependyma
Villi present to increase SA
Active transport of CSF components
Bidirectional (uptake of metabolites into circulatory system

Question 12

Difference between CSF produced in ventricles and from other sites within brain?

Answer 12

Ventricles- responsible for 60% of production, lower K+ and Ca2+, higher Cl-, LOWER Protein(0.18gl/l), pH 7.35

Plasma- 40% of production, HIGHER Protein (75g/l), pH= 7.42

Differences due to regulation by active transport. Very few cells
Idealfor physiological functioning of neurons.

Question 13

Outline the CSF circulation

Answer 13

Lateral ventricles though interventricular formamen

Into third ventricle through cerebral aqueduct

Into fourth ventricle though Luschka and Magendle foramina

INTO CISTERNA MAGNA (Subarachnoid space)

Question 14

What is the functional importance of the subarachnoid space in terms of CSF contact with brain parenchyma?

Answer 14

Transffer of micronutrients into brain

Removal of metabolites

Question 15

Describe the process of the absorption of CSF

Answer 15

CSF pressure must exceed that in venous sinuses (150mm water in SA space, 80mm in venous s)

If venous pressure exceeds CSF pressure the tips of villi close off thus preventing reflux blood into SA space. Arachnoid villi act as 1-way valves

Question 16

Describe the CSF volume

Answer 16

500ml CSF produced/day
Total volume in system =90-140ml (30ml in ventricles, 110ml subarachnoid space)

CSF keeps moving and excess absorbed by arachnoid granulations

Question 17

What are the main functions of CSF?

Answer 17

1. Hydraulic buffer to cushion brain against trauma
2. Vehicle for removal of metabolites from CNS
3. Stable ionic environment for neuronal function (communicates with brain interstitial fluid via pia)
4. Transport of neurotransmitters and chemicals

Question 18

Describe the colour of CSF and its colour in disease states

Answer 18

CSF normally clear sterile fluid
Discoloured in some pathological states:
Yellow (Xanthocromia)
E.g. Subarachnoid haemorrhage
- Lysis of red blood cells, haemoglobin release
Cloudy
E.g. Multiple sclerosis- Protein content (gamma globulin) increase
Bacterial meningitis - Leukocytes are increased, indicative of infection

Question 19

Briefly describe how CSF is sampled

Answer 19

Taken by lumbar puncture at lumbar cistern (no spinal cord)

In children, in lower lumbar levels to avoid hitting spine- skeleton is slower growing than NS

Question 20

What is hydrocephalus?

Answer 20

Dilation of brain ventricles due to blocked CSF circulation, impaired absorption or over secretion.
Increased intracranial pressure- pressure on surrounding tissues affects neurological function (Symptoms include: headaches, vomiting, visual disturbances, papilledema (swelling of optic disc), seizures, altered cognition, balance and coordination problems)

Congenital or acquired

Question 21

Describe non-communication hydrocephalus

Answer 21

Blockage within the ventricular system
- Due to tumour, cyst, stenosis (e.g. narrowing of cerebral aqueduct)
CSF does not circulate over surface of brain
Surgery: Insert shunt to reduce intracranial pressure
imaging to find out where problem is

Question 22

What is Dandy-Walker syndorme?

Answer 22

Congenital non-communcative hydrocephalus of cerebellum
Obstruction within foramina of 4th ventricle giving symmetrical dilation of lateral, 3rd and 4th ventricle

In infancy, childs head may become enlarged because skull is malleable

Question 23

Describe communication hydrocephalus

Answer 23

obstruction in the arachnoid villi- movemnt of CSF into venous sinuses is impeded e.g. impaired absorption following subarachnoid haemorrhage, trauma or bacteial meningitis