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The ventricular system

1) There are 4 ventricles filled with CSF within the brain
1. 2 lateral ventricles (One in each hemisphere)
2. 3rd ventricle
3. 4th ventricle
2) Lateral ventricles communicate with the 3rd ventricle through interventricular foramina (Foramen of Monro)

3) The 3rd ventricle is connected to the 4th ventricle through cerebral aqueduct (Aqueduct of Sylvius)
1. CA is lined by ependyma & surrounded by central grey matter (Called Central grey)
2. 1.8 cm long
3. Direction of CSF flow is from 3rd to 4th ventricle
4. There’s no choroid plexus in CA
4) The 4th ventricle continues with the central canal of the spinal cord
1. Superiorly : Continues with the 4th ventricle
2. Inferiorly : Extends through the inferior part of the MO & the entire length of the spinal cord (Closed at the lower end)
3. In the conus medullaris, it expands to form the terminal ventricle
4. No choroid plexus in the central canal
5) Ventricles & the spinal canal are line throughout with ependyma & filled with CSF

6) The ventricles have developmentally derived from the cavity of the neural tube

Origin & circulation of the CSF


The ventricles

Choroid plexus
1 in each hemisphere
  Body                               : In parietal lobe
  Anterior horn               : In frontal lobe
  Posterior horn              : In Occipital lobe
  Inferior horn : In temporal lobe 
Projects into the ventricle on its medial aspect of the ventricle
It’s the irregular lateral edge of tela choroidea
Choroid plexus is covered by pia mater & the ventricular cavity is lined by ependyma
Produce CSF
Blood supply is by Choroidal branches of the internal carotid & basilar arteries 
3rd ventricle

Slit like cleft between the 2 thalami
Situated above the roof of the ventricle
Formed from tela choroidea
Produce CSF
Blood supply is by Choroidal branches of the internal carotid & basilar arteries 
Venous blood drains to internal cerebral veins, which unite to form the great cerebral vein 
4th ventricle Anterior to the cerebellum and Posterior to the pons & superior half of the MO
Floor of the 4th ventricle – Inferior to striae medullaris:
  a. Most medially is the hypoglossal triangle (Hypoglossal nucleus is beneath it)
  b. Laterally is the vagal triangle (Dorsal motor nucleus of the vagus is beneath it)
The cavity of the 4th ventricle communicates with the SAS through a single median opening & 2 lateral openings (Permits CSF flow from ventricles to SAS)
Median opening           : Foramen of Magendie
Lateral openings          : Foramina of Luschka

T shaped (Vertical part of T is double)
Formed from tela choroidea
Produce CSF
Blood supply is by posterior inferior cerebellar arteries

Sub arachnoid space

1) The space between the arachnoid mater & pia mater

2) It is filled with CSF & contains large blood vessels of the brain

3) SAS completely surrounds the brain

4) It extends along the cranial & spinal nerves to the point where they leave the skull & vertebral canal, with exceptions:
1. Extends along the olfactory nerves to the mucoperiosteum of the nose
2. Extends around the optic nerve to the eye ball & fuse with the sclera (Central retinal artery & vein cross the sub arachnoid space & enter the optic nerve, therefore when CSF pressure is high the vessels can get compressed)

5) It extends along the cerebral blood vessels as they leave the brain substance & stops where they become arterioles or venules

6) Around the base of the brain, SAS expands to form cisterns
1. Cerebellomedullary cistern
2. Pontine cistern
3. Inter peduncular cistern

7) At the inferior end at extends beyond the spinal cord & form Cauda equina

8) It ends at the level of S2 – S3 vertebrae
The ventricular system The ventricular system Reviewed by Radiology Madeeasy on August 04, 2010 Rating: 5
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