The lining ependyma of each ventricle comes into contact with the surface pia mater allowing the invagination of a mass of blood capillaries --- combination of these capillaries , pia and ependyma constitutes the choroid plexus .
continuous through Interventricular foramen with the small plexus in the third ventricle.
secretes the bulk of the CSF
separate from that in the third and lateral ventricles
only makes a small contribution to the total amount of CSF
CSF is clear, colorless, and odorless fluid
produced within the ventricles secreted by the Choroid plexus
provides mechanical support – protection from pressure changes.
In adults, the total volume of CSF is about 150 ml
Between 400 and 500 mL of CSF is produced and reabsorbed daily.
MENINGES & SPACES
VENOUS SINUSES OF THE DURA MATER
Venous sinuses are network of channels that receive all the venous blood from the brain
Venous sinuses lie b/w the inner and outer layers of the dura ---- Inferior sagittal and straight sinuses are the exceptions
Arachnoid granulations also project into the venous sinuses to return CSF to the bloodstream
Dural venous sinuses
within each cerebral hemisphere
anterior horn - frontal lobe
body --- parietal lobe
posterior horn ---- occipital lobe
inferior horn ---- temporal lobe
Anterior horn and Body:
Corpus callosum and the fornix
Septum pellucidum (thin partition between the fornix and corpus callosum)
Thalamus and Basal ganglia Brain stem
Thalamus Thalamus and Basal ganglia Brain stem
Amygdaloid body Thalamus Tail of Caudate nucleus Head of Caudate nucleus Lentiform nucleus Body of Caudate nucleus
Anterior horn and Body:
Caudate nucleus, thalamus
Fibers of Internal capsule Corpus callosum Left thalamus and basal nuclei, viewed from behind
is the most variably developed and may even be absent.
Lateral ventricles Cingulate sulcus Posterior horn of lateral ventricle Collateral eminence Collateral sulcus Splenium of corpus callosum Tapetum of corpus callosum Optic radiation Callosal radiation
Roof and lateral wall
Tapetum of the corpus callosum
Optic radiation lying against the tapetum in the lateral wall.
Medial wall --- two convexities:
Upper (bulb of the posterior horn)
Splenium of the corpus callosum
Lower (Calcar avis)
If Calcar avis is well developed, it obliterates the posterior horn.
Collateral eminence, produced by the collateral sulcus
Lateral ventricles Inferior horn -- Largest horn
tail of the caudate nucleus, amygdaloid body
Tapetum of corpus callosum
Convexities within Lateral ventricles:
The grey matter at the bottom of a sulci indents the cavity
Such sulci are
Caudate nucleus and thalamus also project into the cavity
Elsewhere the walls of the cavity are formed by white matter of the cerebral hemisphere
Cavity within Diencephalon
slit-like space, lying in the sagittal plane
Two side walls
tuber cinereum median eminence
posterior perforated substance
tegmentum of the cerebral peduncles
Two side walls:
Thalamus Interthalamic adhesion (60% of brains)
Hypothalamus Supraoptic nucleus – ADH
Paraventricular nucleus – Vasopressin/Oxytocin
Subthalamus Subthalamic nucleus
Tuber cinerum Median eminence Infundibulum Posterior pitutary
Aqueduct (of Sylvius)
Cavity within midbrain
Continuous above with third ventricle
leads through the midbrain into the cavity of the fourth ventricle
C-shaped slit in the medial wall of the cerebral hemisphere
convexity – fornix
concavity – thalamus, tail of the caudate nucleus
Invaginated by choroid plexus of lateral ventricle
Tela choroidea (double fold of pia) Pitutary stalk (solid) Infundibulum (hollow )
Reflection of two layers of pia matter
Medially b/w interventricular foramina
Laterally across the upper surface of thalamus
Collectively, the blood vessels within the brain have a very large surface area that promotes the exchange of oxygen, carbon dioxide, amino acids, and sugars between blood and brain.
The blood-CSF barrier is formed by active transport from the blood vessels to the brain- Epithelial cells of joined by tight junctions, form a continuous layer that selectively permits the passage of some substances but not others.
Why do we need this?
no blood/brain barrier
corpora amylacea --- calcify ---- after the age of forty years they normally throw a shadow in radiographs of the skull
displaced calcified pineal indicates a space-occupying lesion above the tentorium
melatonin (a hormone related to serotonin), which in animals and probably in man also has an antigonadotrophic action.
part of the tuber cinereum at the base of the infundibulum is the median eminence — highly important as the site of the neurosecretory cells that control the anterior pituitary, and one of the few regions with no blood/brain barrier