Development of the ventricles Flashcards
Describe the development of the ventricles
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
What is the Foramen of Monro?
Also called the interventricular foramen
Lateral ventricles communicate with the third ventricle through it.
What is the function of the septum pellucidum?
Seperates the lateral ventricles
To what lobes are the different horns associated to?
Anterior horn- frontal lobe
Body- parietal lobe
Inferior horn- temporal lobe
Posterior horn- occipital lobe
Describe the appearance and location of the third ventricle
Sits like cleft beltween thalami
Fornix forms roof
What is the Cerebral aqueduct?
AKA Aqueduct of Svivius
Communication between the third ventricle and the fourth aqueduct
Surrounded by the midbrain (passes through)
Describe the appearance and location of the fourth ventricle
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
Descrobe the fourth ventricle communication
Three foramen exit into subararachnoid spaces (specifically into cisterna magna)
2x Formaen of Luschka (lateral)
1x Foramen of Magendie (middle)
What is the choroid plexus?
Produces CSF
Filters blood from branches of internal carotid and basilar arteries
Present throughout the ventricles (looks like caviar)
Describe the structure of the choroid plexus
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.
Describe the cupidoidal ep.
Specialized ependyma
Villi present to increase SA
Active transport of CSF components
Bidirectional (uptake of metabolites into circulatory system
Difference between CSF produced in ventricles and from other sites within brain?
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.
Outline the CSF circulation
Lateral ventricles though interventricular formamen
Into third ventricle through cerebral aqueduct
Into fourth ventricle though Luschka and Magendle foramina
INTO CISTERNA MAGNA (Subarachnoid space)
What is the functional importance of the subarachnoid space in terms of CSF contact with brain parenchyma?
Transffer of micronutrients into brain
Removal of metabolites
Describe the process of the absorption of CSF
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
Describe the CSF volume
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
What are the main functions of CSF?
- Hydraulic buffer to cushion brain against trauma
- Vehicle for removal of metabolites from CNS
- Stable ionic environment for neuronal function (communicates with brain interstitial fluid via pia)
- Transport of neurotransmitters and chemicals
Describe the colour of CSF and its colour in disease states
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
Briefly describe how CSF is sampled
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
What is hydrocephalus?
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
Describe non-communication hydrocephalus
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
What is Dandy-Walker syndorme?
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
Describe communication hydrocephalus
obstruction in the arachnoid villi- movemnt of CSF into venous sinuses is impeded e.g. impaired absorption following subarachnoid haemorrhage, trauma or bacteial meningitis
