Transcript The Brain

Department of Human Anatomy
KNMU
NEUROLOGY
THE
BRAIN
Slide-lecture for students of the 6
Faculty of Medicine
Lector – associate professor
Zharova Nataliya
2015
PLAN
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6.
The meninges of the brain
The brain
The telencephalon
The texture of the cortex of
the cerebral hemispheres
The grey and white matters
The distribution of
functions in the cerebral
cortex
The three meninges of the brain: the dura mater, the arachnoid mater and the pia mater.
Spaces: epidural space is absent, subdural, subarachnoid.
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The cerebral dura mater a
thick whitish connective —
tissue membraine is
outermost in position. It
lines the cranial cavity. It
adheres to the internal
surfaces of the cranial
bones, sending blood
vessels and fibrous
processes into them. The
meningeal layer is falded
inwards as four septa that
partially divide the cranial
cavity into freely
communicating spaces in
which the subdivisuons of
the brain are lodged.
The dura mater consists of the sinuses (10 in number)
and the processes (4 in number)
The processes:
- falx cerebri, between both
cewrebral hemispheres,
anterriorly attached to crista
galli, posteriorly to the
terntorium cerebelli
- tentorium cerebelli, attached the
margins of the transvers sinus
of occipital bone, superior
margins of the pyramids and
temporal bones, Turkish
saddle of the sphenoid bone.
- falx cerebelli, a small, crescentric
fold of dura mater, is below
the tentorium cerebelli,
projecting forwards into the
posterior cerebellar notch.
- diaphragma cellae, is a small,
circular fold of dura mater,
forming a roof to the sella
turcica, almost completely
covering the hypophysis; a
small, central opening in it
transmits the infundibulum.
The dura mater contains several reservoirs collecting blood from the 1. The transverse, the widest
sinus which runs along the
brain; these are the sinuses of the dura mater . The sinuses are venous
posterior margin of the
canals devoid of valves and located in the thickness of the dura mater
tentorium cerebelli. It descends
at the attachment of its processes to the skull. The inflexibility of the
into the sulcus sinus sigmoidei
walls of the venous sinuses provide free drainage of venous activity of
under the name of the
the brain. The venous sinuses are as follows.
2. sigmoid sinus , and at the
jugular foramen is continuous
with the orifice of the internal
jugular vein.
3. The superior sagittal sinus goes
on the superior margin of falx
cerebri for the whole length of
sulcus sinus sagittalis superioris
from crista galli in the internal
occipital protuberance.
4. The occipital sinus is a
continuation, as it were, of the
superior saggital sinus along
the attachment of falx cerebelli
to the internal occipital crest
and along both margins of the
occipital bone.
5. The straight sinus runs on the
line of attachment of falx
cerebri to the tentorium
cerebelli.
6.The inferior sagittal sinus runs on the free lower margin of falx
cerebri and vena cerebri magna.
7. The cavernous sinus is
located on the base of
the skull lateral to the
sella turcica. It is
connected with the
intercavernous sinuses
, passing in front of
and behind the
hypophyseal fossa.
The cavernous sinus
receives the superior
ophthalmic vein, as
well as the inferior
end of the
8.sphenoparital sinus
running on the margin
of the lesser wing of
the sphenoid bone.
The cavernous sinus is
drained of blood by
two sinuses locared
behind it, namely the
9.superior and
10.inferior petrosal
sinuses .
Blood drains from the sinuses into the internal jugular veins.
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The sinuses are
also connected
with the veins of
the outer surface
of the skull through
emissary veins
transmitted
through openings
in the skull bones.
The diploic veins
and the veins of
the spongy
substance of the
cranial bones also
drain into the
sinuses of the dura
mater, while their
other end may be
connected with the
veins on the
external surface of
the head.
The arachnoid mater a delicate membrane enveloping the brain, lies between
the pia and dural meninges, separated from the dura mater by the subdural
space. It is separated from the pia mater be the subarchnoidal space, which is
filled with cerebrospinal fluid. The arachnoid surrounds the beginnings of the
cranial nerves.
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On the upper surface
of the brain the
arachnoid is thin, but
it is thicker on the
basal aspect of the
brain. Wherever the
brain and cranium are
not closely adapted,
the arachnoid is
separated from the
pia by wide intervals,
named subarachnoid
space of which they
are merely
dilatations.
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The arachoid mater
has cisterns
- cerebromedullar
- interpeduncular
- chiasmatic
- cistern of the lateral
sulcus
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The subarachnoid space is connected with the ventricles of the brain by
three openings: the median apertura (apertura mediana) in the median
plane in the inferior part of the roof of the fourth ventricle and the two
lateral apertures (apertura laterales) at the ends of that ventricle's lateral
recessus.
The arachnoid granulations
are small elevations,
usually occurring in
clusters near the superior
sagittal, transverse
sinuses. They protrude
into the sagittal sinus and
its venous lacunae. Fluid
injected into the
subarachnoid space
passes into the
granulationes and their
villi and thence into the
venous sinuses of the
dura by osmosis.
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The pia mater closely
envelopes the brain. It is
a vascular membrane, a
plexus of minute blood
vessels held together by
fine loose connective
tissue.
The cerebrospinal fluid is a clear fluid. It is secreted into the ventricles of the brain by the
choroid plexuses and into the subarachnoid space by plexuses in the fourth ventricle's lateral
recesses.
From the
ventricles it
escapes through
the apertures of
the fourth
ventricle into the
cerebello —
medullary cistern
of the
subarachnoid
space.
Intracranially the
fluid reaches the
arachnoid villi of
the superior
sagittal sinus,
there reentering
the bloodstream.
The cerebral arterial circle (of Willis):2 anterior cerebral arteries, 1 anterior communicating
artery, 2 posterior communicating arteries, 2 posterior cerebral arteries.
The veins of the brain are divided into superficial and deep veins. The
superficial veins collect blood from the cerebral cortex and drain partly into
the superior sagittal sinus and partly into the transverse sinus and the
sinuses on the base of the skull.
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The deep veins receive
blood from the central
grey nuclei and the
ventricles of the brain
and merge to form
one great cerebral
vein. The veins of
cerebellum compose
the superior and the
inferior veins. The
superior veins drain
blood into the straight
sinus and the great
cerebral vein. The
inferior veins drains
into the transverse,
sigmoid, and inferior
petrosal sinus.
The Brain (encephalon) together with membranes surrounding it is located in the cranial cavity.
That is why the convex surface of the brain conforms to the internal concave surface of the arch
of the cranium. The inferior surface of the brain is contiguous to the internal base of the skull. It
has a complex relief, which conforms to the cranial fossae.
The largest parts of the brain are
the hemispheres of the
telencephalon (cerebral
hemispheres), the brainstem and
the cerebellum. The
diencephalon, the
metencephalon (midbrain), the
pons and the medulla oblongata
form the brainstem.
The surface of the cerebral
hemispheres is divided into four
lobes corresponding to the
names of the skull plates that
protect them: the frontal lobe,
parietal lobe, temporal lobe, and
the occipital lobe. In addition to
these four lobes, a fifth lobe
exists called the insula. This lobe
is internal and is not visible from
the surface of the brain.
The frontal lobes are sometimes associated with what it means to be human. Absence of
the frontal lobes typically results in a person who is deemed emotionally shallow,
listless, apathetic, and insensitive to social norms.
Control of movement is associated with the frontal lobes via the primary motor cortex
located within this lobe.
The parietal, temporal, and occipital lobes are specialized for perception. Within the
parietal lobe is the primary somatosensory cortex which receives information
pertaining to the senses of the body: touch, pressure, temperature, and pain. Visual
information is received by the primary visual cortex located within the occipital lobe.
Hearing is processed in the primary auditory cortex within the temporal lobe. The
central sulcus (fissure of Rolando) divides the frontal lobe from the parietal lobe. The
lateral fissure (fissure of Sylvius) separates the temporal lobe from the overlying
frontal and parietal lobes. The parieto-occipital fissure separates the parietal and
occipital lobes.
• The grey matter of hemispheres consist of the cerebral cortex, which is
relatively new and basal nuclei –the older structures. The cortex is consist
6 layers:
• 1. the molecular layer
• 2. the external glandular layer
• 3. the external pyramidal layer
• 4. the internal glandular layer
• 5. the internal pyramidal layer
• 6. the multiform layer
• The white matter of the hemispheres appear as quite a thick layer
between the cerebral cortex and basal nuclei. It consist of nerve fibers
arranged into three systems – association (short and long: superior,
inferior, cingulum, uncinate fasciculus), commissural, projection pathways.
The corpus callosum is the primary connection between the left and right
hemispheres of the cerebral cortex. Connection between the two halves takes place
through axons that unite geographically similar regions of the two cerebral cortices.
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The basal nuclei:
1.corpus striatum –
1)caudate nucleus:
head, body, tail;
2)lentiform nucleus:
putamen,
globus pallidus;
2.claustrum
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3.amygdaloid body
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The basal ganglia play a central role in a number of neurological conditions, including several movement
disorders. The most notable are Parkinson's disease, which involves degeneration of the dopamineproducing cells in the substantia nigra pars compacta, and Huntington's disease, which primarily involves
damage to the striatum. Basal ganglia dysfunction is also implicated in some other disorders of behavior
control such as Tourette syndrome, hemiballismus, obsessive–compulsive disorder, and Wilson's disease.
The functions of the basal nuclei:
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The corpus striatum is the main center of an extrapyramidal system. An extrapyramidal (intrapyramidal)
system is a set of the nuclei of the brain and their projective descendent conduction tracts, which make
involuntary (automatic) regulation of the impelled acts and muscular tension.
The functions of the extrapyramidal system include maintenance of a pose, organization of the impelled
expression of emotions.
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All the parts of the extrapyramidal system have diverse communications ensuring realization of the
complex impelled actions.
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The corpus striatum has some functional differences. The globus pallidus equally with the substantia
nigra the red nucleus of the midbrain represents the primary motor center. Involuntary rhythmic motor
activity of the newborns is connected with these formations.
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The putamen and the caudate nucleus receive proprioceptive impulses from the cerebellum and
thalamus. These nuclei coordinate movements on more high level than the corpus striatum. The
appearance of the emotional activity of a child is connected with function of the putamen and the
caudate nucleus. When these nuclei are injured excessive and involuntary movements and (grimacing,
convulsive contraction of muscles) reduction of muscular tension appear.
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The claustrum is connected with the olfactory brain, the cortex of the hemisphere of the cerebrum and
the thalamus by nervous path ways. The functions of the claustrum are not finally found out.
The corpus callosum
is the primary
connection between
the left and right
hemispheres of the
cerebral cortex.
Connection between
the two halves takes
place through axons
that unite
geographically similar
regions of the two
cerebral cortices.
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Under the corpus callosum there is a fornix.
The fornix consists of a body, a column, a crus, a taenia of the fornix. The body of the fornix
lies directly under the posterior part of the corpus callosum. On the lateral side of the body
of the fornix a vascular plexus of the lateral ventricle is situated. Its epithelium layer is
spliced with the fornix. The inferior surface of the body of the fornix adjoins to the thalamus.
The right and the left bodies of the fornix are connected by means of cross fibres which have
received the name of comissure of the fornix (David's lyra). From ahead the body of the
fornix is abruptly bent downwards and continues into the column.
The lateral ventricles. Situated in both hemispheries
below the callous body.
The parts: - central part, through the parietal lobe.
- anterior horn, in frontal lobe.
- inferior horn, into temporal lobe.
- posterior horn, into occipital lobe.
The walls: The superior wall of all horns and central part
formed by the fibres of the callous body.
The walls of anterior horn:
- medial, by septum pellucidum,
- lateral and inferior, by the head of
the caudate nucleus
- superior wall
- anterior – genu of callous body.
The walls of the central part:
- superior wall
- inferior, by the body of the caudate
nucleus and superior part of
thalamus.
- medial, by the body of the fornix.
The walls of the posterior horn:
- superior wall
- medial, by projection of the calcarine
sulcus
- inferior, by trigonum collaterale
The walls of the inferior horn:
- Superior and lateral walls
- medial, by hypocampus
- inferior by collateral sulcus.
Choroid plexus of the lateral horn is situated in its central part and in the inferior horn, it is fastened to the
taenia of the fornix and the fimbria of the hippocampus. The choroid plexus is presented by a rich in blood
capillaries structure projecting into the ventricle's cavity and outwardly.
Between lateral ventricles and third ventricle is situated interventricular foramen (Monro)
As the cerebrum is a gross division with many subdivisions and sub-regions, it is
important to state that this section lists the functions that the cerebrum as a whole
serves. See main articles on cerebral cortex and basal ganglia for more information.
• In general terms it is well understood that the left hemisphere controls
linguistic consciousness, the right half of the body, talking, reading,
writing, spelling, speech communication, verbal intelligence and
memories, and information processing in the areas of math, typing,
grammar, logic, analytic reasoning, and perception of details. The right
hemisphere is associated with 'unconscious' awareness (in the sense it is
not linguistically based), perception of faces and patterns, comprehension
of body language and social cues, creativity and insight, intuitive
reasoning, visual-spatial processing, and holistic comprehension.
Communication between the two hemispheres takes place through the
corpus callosum, which, by the way, is more fully developed in women
than men- likely giving rise to women's intuition.
THE END
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