General anatomy of the brain
2.1 Hersenvliezen (cerebral membranes/meninges)
The brains and the spinal cord lie in meninges that form a bag for water filled with liquor cerebrospinalis. they
consist of 3 different layers (out to inward):
dura mater (hard layer), also called the pachymeninx (pachy= thick)
consists of tough collagen fibers and again divided into two layers:
stratum periostale – grown into periost of skull
stratum meningeale
arachnoidea (spider web layer)
thin layer under which are the blood vessels that go through the subarachnoïdal space
pia mater
lies directly on the brains and goes into the sulci of the brain
Layer 2 and 3 are also together called the leptomeninx (lepto=soft). between these is the subarahnoïdal space which
is filled with liquor cerebrospinalis. In this space lie large brain arteries and vv.cerebri superficiales that go into sinus
sagittalis superior via anchor venes. Near to the sinus you see granulationes arachnoideae which serve for liquor
resorption. You see them a lot in the lacunae laterales which are branches of the sinus superior. The a.meningea lies
between the dura mater and the skull so not in the subarachnoïdal space (see picture).
The dura at a few points goes into the brains. There it forms septa between important brain structures. The falx
cerebri is in the middle of the cerebrum it forms a ‘cave’ for the sinus sagittalis superior. The tentorium cerebelli
divides the cerebrum and the cerebellum. Then we have the falx cerebelli which divides both hemispheres of the
cerebellum (kleine hersenen). The inscisura tentorii is an opening in the tentorium cerebelli for the brain stem to go
through. Because the borders of these meninges are hard and ‘free’ they sometimes can cause hernia of parts of the
brain (beknelling).
The whole dura is attached to the skull in the following manner:
stratum periostale of dura mater is attached to skull periost.
within the dura mater, between periostal en meningeal is where a septa is created in which the venes of the brain
lay (sinus durae matris – ex. sinus sagittalis superior).
walls of these vessels consist of dura mater and endothelial cells
within these vessels we find granulationes Pacchioni which are arachnoidal flocks for liquor resorption
on the dura mater side the arachnoidea has flat cells that (opposed to other meningeal cells) are connected via tight
junctions (neuroendothelium) and form the diffusion barrier .
between arachnoidal and pia mater we have the subarachnoidal space (SAR)
divided by arachnoidal septa that go all the way from A to PM
within the septa lie v. superior cerebri and a. cerebri
Meninges and their cavities
pathological:
epidural space: happens in hematoma of a. meningea media or branches of. Dura mater then disattaches from bone
tissue and so we get epidural hematoma.
subdural space: happens in hematoma of anchor venes. Subdural space between dura mater (meningeal layer) and
arachnoidea layer (neuroendothelium – blood/liquor barrier). So we get a subdural hematoma.
physiological:
subarachnoïdal space: under arachnoïdea layer filled with liquor cerebrospinalis. Can also be pathological when
there are skull base arteries aneurysms.
2.3 Dura mater vascularization and innervation
Most importantly the dura mater is supplied with blood through the a. meningea media which is a branch of the a.
maxillaris. Most important function however of this artery is not blood supply to the meninges but to the calvaria!!!
,Innervation of the dura mater is best just shown in a picture.
3.2 Liquor circulation and cisternae
Liquor is formed in the plexus chorideus which has parts in each of the 4 brain parts. Ith them goes via the aperture
laterales into the SAR that also has expansions which are called cisternae. Then, via the granulationes Pacchioni
(secondary) or via branches of the spinal cord (primary) the fluid is drained to venus plexi or lymph vessels.
In total we have 150 mL of liquor (20% in ventricles and 80% SAR) which is replaced 2/4 times a day completely. So
500 mL is produced each day. When there is more or drainage is impaired pressure in the brain starts to rise.
Histology:
plexus choroideus is made of the ventricle it goes out of. Consists of layer of cubic epithelial cells covered with a brush
layer.
3.3 Tissue barriers in the brain
Blood-brain barrier
normal brain tissue has ependym cells with wide intercellular spaces. There fluid can move through normally
the blood-brain barrier consists of neuroendothelial cells that are tied together by tight junctions at a capillary in the
brains (random)
no paracellular transport of hydrophilic substances in both dyrections
transport mechanisms are needed to transport substances that are important for the brains (glucose)
Blood-liquor barrier
in circumventricular organs (ependymorgans): Neurohypophysis, plexus choroideus, corpus pineale and organum
vasculosum laminae terminales, organum subfronicale/subsommicusurale and are postrema. They are formed by a
modified ependym and lie at the liquor spaces.
In these organs blood from fenestrated! capillaries can move feely out of the lumen into the tissue.
the blood-liquor barrier is formed by the ependyme cells which are tied together by tight junctions the
plexusepithelium
Now that we have crossed all the barriers, we can start looking at the outer structure of the telencephalon. This is
the brain cortex. It is built out of grey substance (substantia grisea).
The cerebral cortex contains the most part of this grey substance and is divided into 2 parts:
isocortex (=neocortex) – consists out of six layers
allocortex (=paleo- and archicortex) – consists out of 3-4 layers
There are also inside structures with grey matter but we discuss them later.
We can divde the two hemispheres of the brain into lobes. the hemispheres are divided by the fissura longtidunalis
cerebri and can both be divided into six lobes.
,Other regional division can be throughnot onl lobi gyri and sulci but microscopicly there are differences between
cells in regions. that is why Brodmann divided the cortex into 45 areas (or more). To know all of their functions is not
do-able but at least the following are important.
1/2/3: primary somatosensoric cortex
4: primary somatomotoric cortex
17: ‘facial’ cortex (area striata)
41/42: primary hearing area
Histology:
The neocortex (six layers from outside to inside)
Lamina molecularis: almost no cells
II/IV. Lamina granularis externa/interna: astrocytes and small pyramid cells
III/V. Lamina pyramidalis externa/interna: pyramid cells (externa small/interna large)
VI. Lamina multiformis: cells with a polymorphous nucleus
There are regions in the core that are responsible for processing information, these are the areas with a large
granular cotrex – somatosensoric. Regions that lead information outwards have broad pyramid cell layers (agranular
cortex) – somatomotoric.
To just talk about the cells:
astrocytes; cells with short axon for processing info at the spot.there are different types of them too.
small pyramid cells: cells with a long axon that ends within the cortex either as (association axon ends in the samen
hemisphere but other part of cortex – commissure axon ends in other hemisphere but same type of region).
large pyramid cells: cells with a long axon that ends out of the cortex
The allocortex.
The allocortex lies around the corpus callosum and it’s structures on the inside of the brain.
, Case 1
The central nervous system (CNS) consists of the brain and spinal cord, which are seamlessly
interconnected and are one functional unit. The CNS communicates with the body via the peripheral
nervous system, whose nerves emerge from the brain and spinal cord (cranial and spinal nerves).
Grey and white matter
Gray matter= neuron cell bodies (perikarya/ somata) +
unmyelinated fibers (collected dendrites). They are interconnected
to form neural networks.
White matter = myelinated fiber tracts (collected axons running in
the same direction) of the neurons, interconnecting different areas
of the brain and spinal cord.
spinal cord= a central cavity surrounded by gray matter, external
to which is white matter. butterfly’’
In the telencephalon gray matter is concentrated superficially = cerebral cortex. The white matteris the
inner part, beneath cortex.
The basal ganglia = deeply situated, scattered islands of gray matter within the white matter
Cerebral white matter =
Association fibers: connect different parts of the same hemisphere
Commissural fibers: connect corresponding gray areas of the two hemispheres
Projection fibers: from the cortex to lower areas or vice versa.
Cerebral grey matter =
Cerebral cortex: see below
Basal nuclei (Caudate - Putamen → caudate+ putamen = striatum/striated body - Globus pallidus)
They play a role in cognition and emotion. They filter out incorrect or inappropriate responses,
passing only the best response on to the cortex. For example, in motor activity, the basal nuclei are
particularly important in starting, stopping, and monitoring the intensity of movements executed by
the cortex, especially those that are relatively slow or stereotyped, such as arm-swinging during
walking. Additionally, they inhibit antagonistic or unnecessary movements. Disorders of the basal
nuclei result in either too much movement (as in Huntington’s disease) or too little movement
(Parkinson’s disease).
Macroscopic organisation of the brain
Microscopic organisation of the brain
2.1 Hersenvliezen (cerebral membranes/meninges)
The brains and the spinal cord lie in meninges that form a bag for water filled with liquor cerebrospinalis. they
consist of 3 different layers (out to inward):
dura mater (hard layer), also called the pachymeninx (pachy= thick)
consists of tough collagen fibers and again divided into two layers:
stratum periostale – grown into periost of skull
stratum meningeale
arachnoidea (spider web layer)
thin layer under which are the blood vessels that go through the subarachnoïdal space
pia mater
lies directly on the brains and goes into the sulci of the brain
Layer 2 and 3 are also together called the leptomeninx (lepto=soft). between these is the subarahnoïdal space which
is filled with liquor cerebrospinalis. In this space lie large brain arteries and vv.cerebri superficiales that go into sinus
sagittalis superior via anchor venes. Near to the sinus you see granulationes arachnoideae which serve for liquor
resorption. You see them a lot in the lacunae laterales which are branches of the sinus superior. The a.meningea lies
between the dura mater and the skull so not in the subarachnoïdal space (see picture).
The dura at a few points goes into the brains. There it forms septa between important brain structures. The falx
cerebri is in the middle of the cerebrum it forms a ‘cave’ for the sinus sagittalis superior. The tentorium cerebelli
divides the cerebrum and the cerebellum. Then we have the falx cerebelli which divides both hemispheres of the
cerebellum (kleine hersenen). The inscisura tentorii is an opening in the tentorium cerebelli for the brain stem to go
through. Because the borders of these meninges are hard and ‘free’ they sometimes can cause hernia of parts of the
brain (beknelling).
The whole dura is attached to the skull in the following manner:
stratum periostale of dura mater is attached to skull periost.
within the dura mater, between periostal en meningeal is where a septa is created in which the venes of the brain
lay (sinus durae matris – ex. sinus sagittalis superior).
walls of these vessels consist of dura mater and endothelial cells
within these vessels we find granulationes Pacchioni which are arachnoidal flocks for liquor resorption
on the dura mater side the arachnoidea has flat cells that (opposed to other meningeal cells) are connected via tight
junctions (neuroendothelium) and form the diffusion barrier .
between arachnoidal and pia mater we have the subarachnoidal space (SAR)
divided by arachnoidal septa that go all the way from A to PM
within the septa lie v. superior cerebri and a. cerebri
Meninges and their cavities
pathological:
epidural space: happens in hematoma of a. meningea media or branches of. Dura mater then disattaches from bone
tissue and so we get epidural hematoma.
subdural space: happens in hematoma of anchor venes. Subdural space between dura mater (meningeal layer) and
arachnoidea layer (neuroendothelium – blood/liquor barrier). So we get a subdural hematoma.
physiological:
subarachnoïdal space: under arachnoïdea layer filled with liquor cerebrospinalis. Can also be pathological when
there are skull base arteries aneurysms.
2.3 Dura mater vascularization and innervation
Most importantly the dura mater is supplied with blood through the a. meningea media which is a branch of the a.
maxillaris. Most important function however of this artery is not blood supply to the meninges but to the calvaria!!!
,Innervation of the dura mater is best just shown in a picture.
3.2 Liquor circulation and cisternae
Liquor is formed in the plexus chorideus which has parts in each of the 4 brain parts. Ith them goes via the aperture
laterales into the SAR that also has expansions which are called cisternae. Then, via the granulationes Pacchioni
(secondary) or via branches of the spinal cord (primary) the fluid is drained to venus plexi or lymph vessels.
In total we have 150 mL of liquor (20% in ventricles and 80% SAR) which is replaced 2/4 times a day completely. So
500 mL is produced each day. When there is more or drainage is impaired pressure in the brain starts to rise.
Histology:
plexus choroideus is made of the ventricle it goes out of. Consists of layer of cubic epithelial cells covered with a brush
layer.
3.3 Tissue barriers in the brain
Blood-brain barrier
normal brain tissue has ependym cells with wide intercellular spaces. There fluid can move through normally
the blood-brain barrier consists of neuroendothelial cells that are tied together by tight junctions at a capillary in the
brains (random)
no paracellular transport of hydrophilic substances in both dyrections
transport mechanisms are needed to transport substances that are important for the brains (glucose)
Blood-liquor barrier
in circumventricular organs (ependymorgans): Neurohypophysis, plexus choroideus, corpus pineale and organum
vasculosum laminae terminales, organum subfronicale/subsommicusurale and are postrema. They are formed by a
modified ependym and lie at the liquor spaces.
In these organs blood from fenestrated! capillaries can move feely out of the lumen into the tissue.
the blood-liquor barrier is formed by the ependyme cells which are tied together by tight junctions the
plexusepithelium
Now that we have crossed all the barriers, we can start looking at the outer structure of the telencephalon. This is
the brain cortex. It is built out of grey substance (substantia grisea).
The cerebral cortex contains the most part of this grey substance and is divided into 2 parts:
isocortex (=neocortex) – consists out of six layers
allocortex (=paleo- and archicortex) – consists out of 3-4 layers
There are also inside structures with grey matter but we discuss them later.
We can divde the two hemispheres of the brain into lobes. the hemispheres are divided by the fissura longtidunalis
cerebri and can both be divided into six lobes.
,Other regional division can be throughnot onl lobi gyri and sulci but microscopicly there are differences between
cells in regions. that is why Brodmann divided the cortex into 45 areas (or more). To know all of their functions is not
do-able but at least the following are important.
1/2/3: primary somatosensoric cortex
4: primary somatomotoric cortex
17: ‘facial’ cortex (area striata)
41/42: primary hearing area
Histology:
The neocortex (six layers from outside to inside)
Lamina molecularis: almost no cells
II/IV. Lamina granularis externa/interna: astrocytes and small pyramid cells
III/V. Lamina pyramidalis externa/interna: pyramid cells (externa small/interna large)
VI. Lamina multiformis: cells with a polymorphous nucleus
There are regions in the core that are responsible for processing information, these are the areas with a large
granular cotrex – somatosensoric. Regions that lead information outwards have broad pyramid cell layers (agranular
cortex) – somatomotoric.
To just talk about the cells:
astrocytes; cells with short axon for processing info at the spot.there are different types of them too.
small pyramid cells: cells with a long axon that ends within the cortex either as (association axon ends in the samen
hemisphere but other part of cortex – commissure axon ends in other hemisphere but same type of region).
large pyramid cells: cells with a long axon that ends out of the cortex
The allocortex.
The allocortex lies around the corpus callosum and it’s structures on the inside of the brain.
, Case 1
The central nervous system (CNS) consists of the brain and spinal cord, which are seamlessly
interconnected and are one functional unit. The CNS communicates with the body via the peripheral
nervous system, whose nerves emerge from the brain and spinal cord (cranial and spinal nerves).
Grey and white matter
Gray matter= neuron cell bodies (perikarya/ somata) +
unmyelinated fibers (collected dendrites). They are interconnected
to form neural networks.
White matter = myelinated fiber tracts (collected axons running in
the same direction) of the neurons, interconnecting different areas
of the brain and spinal cord.
spinal cord= a central cavity surrounded by gray matter, external
to which is white matter. butterfly’’
In the telencephalon gray matter is concentrated superficially = cerebral cortex. The white matteris the
inner part, beneath cortex.
The basal ganglia = deeply situated, scattered islands of gray matter within the white matter
Cerebral white matter =
Association fibers: connect different parts of the same hemisphere
Commissural fibers: connect corresponding gray areas of the two hemispheres
Projection fibers: from the cortex to lower areas or vice versa.
Cerebral grey matter =
Cerebral cortex: see below
Basal nuclei (Caudate - Putamen → caudate+ putamen = striatum/striated body - Globus pallidus)
They play a role in cognition and emotion. They filter out incorrect or inappropriate responses,
passing only the best response on to the cortex. For example, in motor activity, the basal nuclei are
particularly important in starting, stopping, and monitoring the intensity of movements executed by
the cortex, especially those that are relatively slow or stereotyped, such as arm-swinging during
walking. Additionally, they inhibit antagonistic or unnecessary movements. Disorders of the basal
nuclei result in either too much movement (as in Huntington’s disease) or too little movement
(Parkinson’s disease).
Macroscopic organisation of the brain
Microscopic organisation of the brain
