Download NEURO ANATOMY

‫‪NEURO ANATOMY‬‬
‫‪27/11/2013‬‬
‫االربعاء‬
‫أ‪.‬د‪.‬عبد الجبار الحبيطي‬
The Pons
Is the middle part of the brain stem (also a part of the hind
brain) its pos. surface forms the upper 1/2 of the floor for the 4th
ventricle, the pons lies in contact with the clivus (basilar part of
the occipital bone, body of sphenoid & dorsum sellae) its
ventral (basilar) surface bulges anteriorly and is continuous
laterally with the middle cerebellar peduncle on each side.
The basilar part
 Is grooved by a longitudinal median sulcus (basilar sulcus)
which lodges the basilar artery, it is continuous on each side
(just outside the attachment of trigeminal nerve) as middle
cerebellar peduncle.
 The pons is continuous above with the 2 crura of the mid
brain & below with the 2 pyramids of the medulla oblongata.
 The bulge of the basilar part is due to (produced by):
i.
ii.
iii.
Large no. of pontine nuclei.
Descending corticopontine, corticospinal & corticonuclear fibers.
Pontocerebellar fibers which goes to cerebellum via the middle
cerebellar peduncle.
 The trigeminal nerve is the only cranial nerve attached to the surface;
it is seen at the junction between the basilar part & the middle
cerebellar peduncle.
The dorsal (tegmental) part
 Forms the upper 1/2 of the floor of the 4th ventricle, is
continuous above with the tegmentum of the mid brain &
below with the pos. surface of the upper 1/2 of the medulla
oblongata.
 It contains the nuclei of the middle 4 cranial nerves (5th -8th)
and also contains 4 sensory lemnisci (medial, lateral, spinal
& trigeminal).
The posterior surface of the
Pons shows the following
features
1.
2.
3.
4.
5.
6.
Pos. median sulcus.
On each side of which there is a vertical band of swelling
called medial eminence.
At the lower part of the medial eminence we can see the
facial colliculus contains the nucleus of the abducent nerve.
Each medial eminence is limited laterally by sulcus known as
sulcus limitance.
At the upper part of sulcus limitance there is a pigmented
area known as substantia ferrigenea.
Lateral to the sulcus limitance there is vestibular area
contains some vestibular nuclei.
Nuclei in the Pons
1.
I.
II.
Nuclei of trigeminal nerve ( 4 nuclei ) : Motor nucleus: - gives motor fibers that join the
mandibular nerve to supply the muscles of mastication,
mylohyoid & ant. Belly of digastric. in addition to the
nerves to the tensor palati & tensor tympani muscles
Main sensory nucleus : it receive touch sensation form
the trigeminal area (side of the face and scalp)
III. Mesencephalic nucleus: - receives proprioceptive
sensation from the muscles of mastication, face & eye ball.
IV. Spinal nucleus: receive fibers of the spinal tract of
trigeminal nerve (pain & temperature from the same side of the
face and scalp).
2- Nucleus of the abducent nerve: - at the bottom of the facial
colliculus and it is surrounded by fibers of facial nerve as they arise
from the facial nerve nucleus , they loop around the abducent nerve
creating a swelling called the facial colliculus
3- Nuclei of facial nerve (3 in number): - One motor, one
parasympathetic (superior salivary) both of these nuclei lie in the
Pons, while the 3rd nucleus (I.e. sensory for taste, the solitarius) lies in
the medulla oblongata. Superior salivary nucleus gives fibers
distributed via chorda tympanic (sublingual & submandibular) & greater
superficial petrosal (to lacrimal & nasal glands).
4- Nuclei of vestibulo-cochlear nerve: - Vestibular & cochlear nuclei.
The midbrain
 The cerebral peduncle is divided into crus cerebri and
tegmentum by the substantia nigra.
 The crus contains the following descending tracks: I.
Cortico-spinal fibers: - occupy the middle 3/5th of the
crus cerebri.
II. Cortico-nuclear fibers: - situated medially to the Corticospinal.
III. Cortico-pontine fibers: - occupy the medial 1/5th and the lateral
1/5th of the crus according to the site of origin of these fibers, the fibers
coming from the frontal lobe occupy the medial 1/5th, while those
coming from the occipital and temporal lobes occupy the lateral 1/5th of
the crus (there will form Cortico-ponto-cerebellar pathway from cerebral
cortex to cerebellar cortex).
 Substantia nigra separates the crus cerebri from the tegmentum &
is an important extrapyramidal centre.
Each crus cerebri has the following relations: Laterally : on each side
Trochlear nerve , optic tract (cross the crus from behind forward )
Some blood vessels (posterior cerebral , superior cerebellar
arteries and basal vein)
Medially :
 Posterior perforated substance (pierced by striate or central
branches).
Occulomotor nerve
The tegmentum
Is continuous below with the tegmental part of the Pons, the
part of the tegmentum at the level +of the superior colliculus
contains red nucleus (an important extrapyramidal centre),
While at the level of inferior colliculus the tegmentum receives
the decussation of the 2 superior cerebellar peduncles.
The nuclei in the midbrain
I.
II.
III.
The nucleus of the occulomotor nerve : at the level of
superior colliculus , it is a motor nucleus supplies 5 of the
extra-ocular muscles , and also contains edinger-westphal
nucleus as a parasympathetic part whose fibers goes to
ciliary ganglion to supply constrictor pupillae muscle and
ciliary body .
Nucleus of the trochlear nerve: - in the lower part of
midbrain at the level of inf. Colliculus.
Red nucleus: - in the tegmentum at the level of sup.
Colliculus , it receives afferent from the frontal cortex , corpus
striatus and cerebellum , while it sends efferent as: -
Rubro-veticular
Rubro-spinal
Rubro-thalamic
Fibers or tracts
The cerebellum
It lies in the posterior cranial fossa, behind the Pons and
medulla oblongata and encloses with them the 4th ventricle. It
has two surfaces (sup. and inf.), two notches (the ant. and pos.
– the anterior one receives the back of the brain stem, while
the posterior receives the falx cerebelli). It consist of two
hemispheres connected by narrow median vermis, the part of
vermis seen from above is the superior vermis, while that seen
from inferior surface is the inferior vermis.
 The outer cortex grey mater is highly folded with numerous
transversely running fissures, the part of cortex between the
fissures are called the folia of cerebellum.
 The superior surface shows fissure prima that separates
anterior lobe from middle lobe. The inferior surface shows a
depressed area called vallecula, at the bottom of this
vallecula the inferior vermis lies (forms by nodule, uvula &
pyramid). The inferior surface also shows the tonsil of
cerebellum situated on each side of the inferior vermis.
Cerebellum has three fissures
A.
B.
C.
Fissure prima: - intervenes between the anterior lobe
and the middle lobe.
Postero-lateral fissures: - lies on the inferior surface
between the flocculo-nodular lobe and middle lobe.
Horizontal fissure: - extends along the lat. & pos. border
of the hemisphere between the superior and inferior
Borders of the hemisphere.
Lobes of the cerebellum
A.
B.
C.
Anterior lobe: - in front of the fissure prima and its part
that extending above the superior medullary velum is
called the lingula.
Middle lobe: - extends from fissure prima and posterolateral fissure, the tonsil is part of this lobe.
Flocculo-nodular lobe : consist of the nodule of the
vermis and two floculli one on each side
Functional division of
cerebellum
1.
2.
3.
Archi-cerebellum: - include flocculo-nodular lobe and the
lingula, related to vestibular apparatus.
Paleo-cerebellum : is the anterior lobe minus the lingula
and is connected to the spinal cord
Neo-cerebellum: - consists of the middle lobe and is
connected with cerebral cortex via the ponto-cerebellar
pathway
Blood supply of the cerebellum
I. Superior cerebellar artery
II. Anterior inferior cerebellar artery From basilar artery
III. Posterior inferior cerebellar artery From vertebral artery
 The medulla of cerebellum contains four intracerebellar
nuclei arranged from lateral to medial as dentate,
emboliform, globose and fastegial nuclei embedded within
the white mater of cerebellum.