Download Lec.9د.عبد الجبار الحبيـطي The basal ganglia (nuclei)

Neuro Anatomy
Lec.9‫احلبيـطي‬
‫عبد اجلبار‬.‫د‬
The basal ganglia (nuclei): Is a collection of small masses of gray matter situated
within the white matter (medulla) of each cerebral
hemisphere as dispersed masses, the internal capsule
passes between these nuclei & separated them from each
other. They include: I- Corpus striatum.
II- The amygdaloid nucleus.
III- The claustrum.
The corpus striatum is situated lateral to the thalamus, it
is completely divided by the internal capsule into: iThe caudate nucleus.
ii- The Lentiform nucleus.
i-
The caudate is coma shaped mass which is closely
related to the lateral ventricle & lies lateral to the
thalamus. It has the following parts: - head, body &
tail.
 The head lies in the floor of the anterior horn &
being separated from the lentiform nucleus by the
anterior limb of the internal capsule. It is supplied
by striate branches of the middle & anterior
cerebral arteries.
 The body runs in the floor of the central part of
the lateral ventricle.
 Tail is long & narrow part, it curves behind the
thalamus to run in the roof of the inferior horn. It
terminates by fusing with the amygdaloid nucleus
just above the tip of the inferior horn.
ii-
The lentiform nucleus is a relatively large lens-like
mass & lies lateral to the thalamus & separated from
it by the posterior limb of the internal capsule. It has
3 surfaces; lateral, medial & inferior.
The lateral surface is separated from the claustrum
by the external capsule. The medial surface is convex
& being separated from both head of caudate &
thalamus by the anterior & posterior limbs of the
internal capsule respectively. The inferior surface lies
over the fibers of the auditory radiation.
The lentiform nucleus is subdivided into 2 parts: iPutamen is the dark lateral part of the lentiform
ii-
nucleus.
Globus pallidus is the pale medial part of the
lentiform nucleus.
The caudate & putamen receive afferents from: a- Cerebral cortex (mainly from pre-motor area).
b- Thalamus (mainly medial nucleus).
While the Globus pallidus gives efferent to: a- Thalamus.
b- Hypothalamus.
c- Sub thalamus.
d- Tegmentum of mid brain.
e- Reticular formation of the brain stem.
Claustrum: -thin plate of gray matter lies lateral to lentiform
where it is separated from it by external capsule. It also
separated from the cortex of insula by the sub-cortical
white matter of the insula.
Amygdaloid: -located over the tip of inferior horn, it is fused
with the tail of caudate, uncus&stria terminals. It receives
afferent from the olfactory system & sends efferent to
stria terminals.
The Cerebrospinal Fluid
Is the fluid present in the ventricles of the brain and in the
subarachnoid spaces around the brain and spinal cord.The
C.S.F of the ventricular system is completely separated
from that present in the subarachnoid spaces.The only
place where the C.S.F of ventricular & subarachnoid
spaces are mixed together is in the Dural sac (Terminal or
5th ventricle) below the lower end of the spinal cord.
Production of C.S.F is
1-Mainly by active secretion from the choroid plexus of
the ventricles.
2-Some may originate as tissue fluids formed in the brain
substance .
Drainage:
1-Via arachnoid granulation &Velli to the venous sinuses.
2-Some of it is absorbed directly by the veins present in
the subarachnoid spaces.
3-Some of is drained to out side by perineural lymphatic
vessels.
Circulation
That secreted by the choroid plexus of the lateral ventricle
will pass via foramen of Monro to the 3rd ventricle where
the choroid plexus of this ventricle add some fluid to it
from its choroid plexus,then it pass via cerebral aquidut of
Mid brain to reach the 4th ventricle and the choroid plexus
of this ventricle will add to it some amount produced here
then the C.S.F will pas in either direction as :
A-Some will leave to the central canal of the spinal cord
via the opening at the lower half of the Medulla Oblongata
to reach eventually the Dural Sac.
B-The other will escape to the subarachnoid spaces via
median aperture(of Magendi) and the 2 lateral apertures
of Luschka to reach the Cisterna magna and Cisterna
pontis respectively and from here will circulate in the
subarachnoid spaces around the brain and spinal cord
which eventually reach the Dural Sac.
It is produced at a rate of 0.5 ml per minute and total
volume of the C.S.F is around 140 ml which can be
replaced completely within 4-5 hours.
If the fluid is too much results in Hydrocephalus which
could be due to :
1-Excessive production as in cases of tumours of the
choroid plexus of the ventricles.
2-Delayed drainage due to blochage at some foramena in
the roof of the 4th ventricle or along its course of drainage
as by tumour compressing foramen of Monro or the
cerebral aqueduct.
Blood brain barrier
Is present between the blood vessels and the
extracellular spaces of the brain it is formed by:
1-Endothelial cells in the blood capillaries.
2-Continuos basement membrane surrounding blood
capillaries.
3-Foot processes of Astrocytes.