Lec:9
Page 1
Neuro-Anatomy
Lec: 9 Prof Dr. Al-Hubaity
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 and separates them from
each other. They include:
1- Corpus striatum.
2- The amygdaloid nucleus.
3- The claustrum
The corpus striatum is situated lateral to the thalamus, it is completely
divided by the internal capsule into:
a- The caudate nucleus.
b- Lentiform nucleus.
The caudatenucleus is coma shaped mass which is closely related to the
lateral ventricle and lies lateral to the thalamus. It has the following parts:
head, body and tail
The head lies in the floor of the anterior horn and being separated
from the lentiform nucleus by the anterior limb of the internal
capsule. It is supplied by striate branches of middle and anterior
cerebral arteries.
The body runs in the floor of the central part of the lateral
ventricle.
Tail is long and 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.
Lec:9
Page 2
The lentiform nucleus is a relatively large lens-like mass and lies lateral
to the thalamus and separated from it by the posterior limb of the internal
capsule. It has 3 surfaces; lateral, medial and inferior
The lateral surface is separated from the claustrum by the external
capsule.
The medial surface is convex and being separated from both head
of caudate and thalamus by the anterior and posterior limbs of the
internal capsule respectively
The inferior surface lies over the fibers of the auditory radiation.
The lentiform nucleus is subdivided into two parts:
A- Putamen, is the dark lateral part of the lentiform nucleus
B- Globus pallidus, is the pale medial part of the lentiform.
The caudate and putamen receive afferents from:
1- Cerebral cortex (mainly from premotor area).
2- Thalamus (mainly medial nucleus).
While globus pallidus gives efferent to:
1- Thalamus
2- Hypothalamus
3- Subthalamus
4- Tegmentum of mid brain
5- 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 tail of
caudate, uncus and stria terminalis. It receives afferent from the olfactory
system and sends efferent to stria terminalis.
Lec:9
Page 3
The lateral ventricle
Is the cavity inside each cerebral hemisphere.It consist of a central part or
body (in the parietal lobe) and 3 horns; anterior, posterior and inferior
horns. The lateral ventricles communicate with the 3rd ventricle via
interventricular foramen (of monro).
The anterior horn, passes forward into the frontal lobe just in front of the
level of foramen of monro and has the following boundaries:
1- Roof by the most anterior part of the body of corpus callosum and
is limited by the genue.
2- Floor by the rostrum of corpus callosum, and head of caudate
nucleus mainly in addition the paraterminal gyrus can share in the
floor.
3- Medial wall by septum pellucidum and anterior column of fornix.
The central part (body)
Extends from interventricular foramen anteriorly to the level of splenium
posteriorly and is the cavity of parietal lobe, it has the following
boundaries
1- Roof is by the under surface of the body of corpus callosum.
2- Medial wall by septum pellucidum.
3- Floor by followings from lateral to medial:
a) Body of caudate nucleus
b) Thalamostriate vein and stria terminalis (in the groove
between the caudate nucleus and thalamus).
c) A strip of the superior surface of thalamus.
d) Tella choriodea and choroid plexus of the lateral ventricle.
e) Body of the fornix
-in the floor is part of the choroid fissure
Lec:9
Page 4
The posterior horn:
Starts at the level of splenium as an extension of the central part of the
lateral ventricle into the occipital lobe, it has the following boundaries:
1- Roof and lateral wall: mainly by the tapetum and partly by the
optic radiation.
2- The medial wall shows two elevations:
a. Superior one is the bulb of the posterior horn is caused by
the splenial fibers of corpus callosum (forceps major) as
passing posteriorly into the occipital lobe.
b. Inferior swelling is called calcar avis is produced by
calcarine sulcus.
The inferior horn:
Is the continuation of the posterior horn into the temporal lobe, it is
bounded as follows:
1) Roof by:
Tapetum of the corpus callosum.
Tail of caudate nucleus.
Stria terminalis. Both (2) & (3) end into the amygdaloid nucleus.
2) Floor is formed by:
Collateral eminence produced by the collateral sulcus.
Hippocampus and pes hippocampus.
Alveus and fimbria of the hippocampus where it continue as
posterior column of fornix.
Lec:9
Page 5
The Choroid Fissure
Is the slit like gap between the body of the fornix and superior surface
of the thalamus which is situated in the floor of the central part of the
lateral ventricle (through which tella choroidea projects). It is
completed by the temporal part of the fissure between the stria
terminalis and the fimbria of the hippocampus (in this temporal part of
the fissure the lower part of the choroid plexus of lateral ventricle
invaginate).
The choroid plexus of the lateral ventricle receives its blood supply
from:
1- Anterior choroidal artery which is a branch from internal carotid
or middle cerebral.
2- Posterior choroidal artery which is a branch from the posterior
cerebral artery.
Tella choroidea and choroid plexus
The tella choroidea consists of a core of blood vessel (choroidal artery)
surrounded by 2 layers of pia matter to invaginate itself in to the
ventricles.
Choroid plexus: is the invaginated tella choroidea with the epindymal
lining of the ventricle. Therefore choroid plexus consists of:
1. Vascular core.
2. Two layers of pia.
3. Ependymal layer.
Lec:9
Page 6
The Third Ventricle
Is a relatively slit like gap between the 2 halves of diencephalon. It is also
called the diencephalon cavity, which splits the diencephalon into 2 halves
connected together across the cavity by the interthalamic connecter. The third
ventricle receives the 2 lateral ventricles above at the interventricular foramen
of (Mouro) and inferiorly communicates with the 4
th
ventricle via the cerebral
aqueduct (of the sylivius of mid brain). It has following boundaries:
Roof: is formed by 2 structures, tella choroidea medially and a strip of
superior surface of thalamus laterally.
Floor: is formed by hypothalamic structures that forms the contents of
interpeduncular fossa includes optic chiasma, median eminence,
tubercinerium, infundibulum and posterior perforated substance
Anterior wall: by lamina terminalis, anterior column of fornix and
optic chiasma.
Posterior wall is formed by the posterior commissure (guarding
the cerebral aqueduct), pineal recess and habenular commissure.
Lateral wall (on each side): is formed by the medial surface of
the thalamus and hypothalamus which are separated by the
hypothalamic sulcus. The two lateral walls are connected
together across the cavity by the interthalamic connector.