PARTS OF CEREBELLUM
Cerebellum consists of a
narrow, worm-like central body called vermis and two
lateral lobes, the right and left cerebellar hemispheres.
VERMIS
Vermis of cerebellum is formed by nine parts. Part of vermis on the upper surface of cerebellum is known as superior vermis and the part on lower surface of cerebellum is called inferior vermis.
Nodulus is continued on either side as an elongated and somewhat lobulated structure called flocculus. Nodulus and flocculi are together called flocculonodular lobe. On either side of pyramid, there is another extension named paraflocculus.
Fissures Present Over the Surface of Vermis
1. Primary
fissure between culmen and lobulus simplex
2.
Prepyramidal fissure between tuber and pyramid
3.
Posterolateral fissure between uvula and nodulus.
CEREBELLAR
HEMISPHERES
Cerebellar hemispheres are
the extended portions on either side of vermis.
Each hemisphere has two
portions:
1. Lobulus
ansiformis or ansiform lobe, which is the larger portion of
cerebellar hemisphere
2. Lobulus
paramedianus or paramedian lobe, which is the smaller portion of
cerebellar hemisphere.
DIVISIONS OF CEREBELLUM
Division of cerebellum into different
major parts is done
by three methods:
A. Anatomical divisions
B. Phylogenetic divisions
C. Physiological or
functional divisions.
ANATOMICAL DIVISIONS
On structural basis, the whole cerebellum is divided into
three portions:
1. Anterior lobe
2. Posterior lobe
3. Flocculonodular lobe.
Anterior Lobe
Anterior lobe includes lingula,
central lobe and culmen. It is separated from posterior lobe
by primary fissure.
Posterior Lobe
Posterior lobe consists of
lobulus simplex, declive, tuber, pyramid, uvula,
paraflocculi and the two portions of hemispheres, viz. ansiform lobe
and paramedian lobe.
Flocculonodular Lobe
Flocculonodular lobe
includes nodulus and the lateral extension on
either side called flocculus. It is separated from rest of the cerebellum by posterolateral fissure.
PHYLOGENETIC
DIVISIONS
Depending upon phylogeny,
the cerebellum is divided
into two divisions:
1. Paleocerebellum
2. Neocerebellum.
Paleocerebellum
Paleocerebellum is the phylogenetically
oldest part of cerebellum. It includes two divisions:
i. Archicerebellum,
which includes flocculonodular lobe
ii. Paleocerebellum
proper, which includes lingula, central lobe, culmen, lobulus simplex,
pyramid,
uvula and
paraflocculi.
Neocerebellum
Neocerebellum
is the phylogenetically newer portion of cerebellum. It includes declive,
tuber and the two portions of
cerebellar hemispheres, viz. lobulus ansiformis and lobulus paramedianus.
PHYSIOLOGICAL OR FUNCTIONAL DIVISIONS
Based on functions, the
cerebellum is divided into three
divisions:
1. Vestibulocerebellum
2. Spinocerebellum
3. Corticocerebellum.
1. Vestibulocerebellum
Vestibulocerebellum
includes flocculonodular lobe that forms the archicerebellum.
2. Spinocerebellum
Spinocerebellum includes lingula,
central lobe, culmen, lobulus simplex, declive, tuber, pyramid, uvula and paraflocculi and medial portions of lobulus ansiformis and
lobulus paramedianus.
3. Corticocerebellum
Corticocerebellum includes
lateral portions of lobules ansiformis and lobulus paramedianus.
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