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Basal Ganglia
Prof. Saleh M. Al-Dhaheri
Head of Human Anatomy & Histology Department
Sana’a University

Introduction
• Definition: It is a collection of nuclear
(grey matter) masses which lie within
white matter of the cerebral
hemisphere.
• Components:
– Extrapyramidal centres:
• Caudate nucleus.
• lentiform or lenticular nucleus (putamen &
globus pallidus).
– A small centre:
• Amygdaloid nucleus.
– Unkown function:
• Claustrum.

External Features of Basal Ganglia
Caudate Nucleus:
• Shape: comma-shape mass of grey matter.
• Parts & relation:
– Head:
• It is the large anterior end.
• It forms the lateral wall of the anterior horn of the lateral ventricle.
• It is fused posteriorly with the lentiform nucleus & below with the
anterior perforated substance.
– Body:
Arches upwards & backwards above & lateral to the
thalamus forming part of the floor of the central part of
the lateral ventricles.
– Tail:
Curves downwards & forwards in the roof of the inferior
horn of lateral ventricles in the temporal lobe. It ends at
the amygdaloid nucleus.

Amygdaloid Nucleus:
• It is a small rounded mass lying in the uncus of the
temporal lobe, joined to the tail of caudate
nucleus.
• It is a small centre.
Lentiform Nucleus:
• Shape: it resembles a biconvex lens.
• Parts → it consists of:
– Putamen: the larger, darker lateral part.
– Globus pollidus: the smaller, paler medial part.
• Surface & relations:
– Medial surface: is highly convex & is related to the
internal capsule which separated the lentiform nucleus
from head of cuadate (anteriorly)

& the thalamus posteriorly.
– Lateral surface: is slightly convex & is related to the
external capsule which separates the lentiform nucleus
from the claustrum & insula.
Claustrum: it is a thin layer of gray matter lying
between the external capsule (medially) & the
white matter of the insula (laterally). Its antero-
inferior part fuses with the amygdaloid nucleus &
anterior perforated substance. Its function is
unknown.
The corpus Striatum it is a name given to:
– Caudate nucleus.
– The lentiform nucleus
– Intervening anterior limb of internal capsule.
They are called so, because they show a striated appearance.

• The External capsule: it is a thin layer of
white matter which cover the outer surface of the
lentiform nucleus & separating it from the
claustrum & the white matter of the insula. Some
of its fibres are probably association fibres
connecting the temporal lobe to the frontal lobe &
parietal lobes.

The corpus Striatum
• It is an important extrapyramidal centre.
• The caudate nucleus putamen represent the
receptor nuclei which receive most afferent fibres.
• The globus pallidus represent the affector part
giving rise to most efferent fibres.
• Connection of corpus Striatum:
– Afferent fibres derived from:
• Cerebral cortex via corticostriate fibres.
● Thalamus via thalamostriate fibres.
• Substantia nigra via nigrostriate fibres.
– Efferent fibres emerge from the globus pallidus which
pass to other extrapyramidal centres as follow:
• Ansa lenticularis. ● Fasciculus lenticularis.
● Subthalamic fasciculus.
Internal Features of Basal Ganglia

Amygdaloid Nucleus: part of the limbic system.
• Afferents: it receives fibres from the olfactory tract.
• Efferent: its fibres constitute the stria termenalis which
passes first backwards in the roof of the inferior horn of the
lateral ventricles then curves forwards in the floor of the
central part of the lateral ventricles. The fibre ends in:
– Septal Nuclei.
– Habenular nuclei.

Level of Section A
Trough cerebral hemisphere

Level of Section B
Trough cerebral hemisphere

Limbic System
• It is formerly name rhinecephalon.
• Definition: it is the name applied to number of
cortical & subcortical structure lying on the medial
surface of the cerebral hemisphere in the form of
an arch (limbus).
• Structure → it consists of:
– Olfactory components:
1. Olfactory bulb tract which reach the following parts of
the limbic system:
• Anterior perforated substance which fibres proceed to the
amygdaloid & habenular nucleus
• The piriform area including the uncus & anterior part of the
hippocampal gyrus.
2. Hippocampal formation: which include: hippocampus,
dentate gyrus, indusium griseum, medial & lateral
longutidunal striae.

3. Paraterminal gyrus: a narrow vertical gyrus lying
below the rostrum of corpus callosum. It is continuous
above with indusium griseum & below with medial
olfactory stria.
4. Septum pellucidum: lying in the median plane just
below the corpus callosum & formed of nerve fibres in
adition to collection of septal nuclei which constitute
part of the limbic system.
5. The fornix: it is the efferent pathway of the
hippocompus which reaches the mammillary body.
– Non-olfactory components:
1- Cingulate gyrus.
2- Parahippocampal gyrus.
Limbic System

• Connections of the limbic system: it
interconnected with the following centers (cerebral
cortex, thalamus, hypothalamus, epithalamus).
• Functions of the limbic system:
1. Reception of olfactory stimuli.
2. Integration of olfactory, visceral sensation.
Limbic System

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