Basic Anatomy of Midbrain & Pons

1. Dr. Farah Rezwana
HMO,Department of
Neurology,DMCH

2. DEVELOPMENTDEVELOPMENT

3. Pons:Pons: The pons develops from the anterior
part of the metencephalon, but it also
receives a cellular contribution from alar part
of the myelencephalon.
Midbrain:Midbrain: The midbrain develops from
mesencephalon. Cells within the midbrain
multiply continually and be compressed to
form cerebral aqueduct.

5. MidbrainMidbrain
Connects the pons and cerebellum with the
forebrain.
It is about 0.8 inch in length
The midbrain is traversed by a narrow channel called
cerebral aqueduct filled with CSF.

6. ANTERIOR SURFACEANTERIOR SURFACE
AnteriorlyAnteriorly, it presents
two large bundles of
fibers, one on each side
of the midline, called
crus cerebricrus cerebri..
The oculomotor nerveoculomotor nerve
emerges from the
medial aspect of the
crus of the same side
The crus cerebri bounds
the interpeduncularinterpeduncular
fossafossa on either side.

7. POSTERIOR SURFACEPOSTERIOR SURFACE
 PosteriorlyPosteriorly, the midbrain
presents four rounded swellings
called colliculi- One Superiorcolliculi- One Superior
and inferiorinferior colliculi one on
each side.
Each colliculus is laterally
related to a ridge called
brachium.brachium.
o Superior and inferiorSuperior and inferior
brachiumbrachium arises from respective
colliculi
o Superior brachium connects the
superior colliculus to laterallateral
geniculate bodygeniculate body
o Inferior brachium connects the
inferior colluculus to medialmedial
geniculate bodygeniculate body
o In the midline below the inferior
colliculus, the trochlear nervetrochlear nerve
emerges which then winds round
the side of the midbrain to reach its
ventral aspectventral aspect

8. Lateral view

9. The midbrain comprises two lateral halves called-
Cerebral pedunclesCerebral peduncles; which is again divided into
1. anterior part- Crus cerebri
2. posterior part -Tegmentum
by a pigmented band of gray matter, substantia nigrasubstantia nigra
The central narrow cavity is called the cerebral aqueduct or
aqueduct of Sylvius, which connects the 3rd
and 4th
ventricles.
The tectum is the part of the midbrain posterior to the
cerebral aqueduct; it has four small surface swellings referred to
previously; these are two superior and two inferior colliculi.

10. TECTUM & TEGMENTUMTECTUM & TEGMENTUM

12. Transverse section at theTransverse section at the levellevel ofof
Superior ColliculiSuperior Colliculi
Superior colliculi
Substantia nigra
Oculomotor
nucleus
Red nucleus
Mesencephalic
nucleus of
trigeminal n.
Edgnger-westphal
nucleus

13. TractsTracts
MotorMotor
Corticospinal
Corticonuclear
Temporopontin
e
Frontopontine
Medial
longitudinal
fasciculas
Decussation of
rubrospinal tract
SensorySensory
Trigeminal
Spinal
Medial

15. TransverseTransverse Section at the levelSection at the level
of Inferior Colliculiof Inferior Colliculi
Substantia
nigra
Troclear
nucleus
Mesencephalic
nucleus of
trigeminal
nerve

16. TractsTracts
MotorMotor
 Corticospinal
 Corticonuclear
 Temporopontine
 Frontopontine
 Medial longitudinal
fasciculas
SensorySensory
 Lateral
 Trigeminal
 Spinal
 Medial lemnisci
 Decussation of
superior cerebellar
peduncles

17. Blood SupplyBlood Supply
 Artery –Artery –
 posterior
cerebral artery
 superior
cerebellar
artery
 basilar artery
 Veins –Veins –
Drained by
 basal or great
cerebral veins

19. PONSPONS
It is situated anteriorly to the cerebellum measuring
about 1 inch in length.
Connects the medulla oblongata to the midbrain.
Its also connects two cerebellar hemispheres and its
name comes from this bridge like appearance.

20. Anterior surface of PonsAnterior surface of Pons
Pons has a convex anterior surface marked by
transversely running fibers which laterally form a bundle
called middle cerebellar peduncle.
Main Features:Main Features:
 The trigeminal nerve emerges from the anterior surface
at its junction with middle cerebellar peduncle.
 Presents a basilar sulcus in the midline which lodges
basilar artery
 In the groove between Pons and the medulla oblongata,
there emerge, from medial to lateral, abducent, facial and
vestibulocochlear nerves.

22. Posterior SurfacePosterior Surface
 Posterior surface
contains median sulcus
which is bounded by
madial eminence on
both sides.
 Inferior end of medial
eminence is slightly
expanded to form facialfacial
colliculuscolliculus, which is
produced by facial nerve
root.
The upper end of sulcus
limitans presents a bluish-
gray coloration called
substantia ferruginosasubstantia ferruginosa..
Area vestibule liesArea vestibule lies

23. Structure of PonsStructure of Pons
Posterior part-
Tegmentum
Anterior part-
Basis pontis
traversed by
running fibers
of Trapezoid
body.

24. Transverse Section Through theTransverse Section Through the
Cranial PartCranial Part
Motor nucleus of trigeminal n.
Sensory nucleus of trigeminal n.
Pontine nuclei
Trapezoid nuclei

25. TractsTracts
MotorMotor
Corticospinal
Corticonuclear
Transverse
pontine fibers
Medial
longitudinal
fasciculas
SensorySensory
Lateral
Spinal
Medial
lemnisci

27. TransverseTransverse section through thesection through the
CaudalCaudal partpart
Facial nucleus
Abducent nucleus
Medial vestibular nucleus
Spinal nucleus of trigeminal nerve
Pontine nuclei
Trapezoid nuclei

28. TractsTracts
MotorMotor
Corticospinal
Corticonuclear
Transverse pontine
fibers
Medial
longitudinal
fasciculas
SensorySensory
Spinal tract of
trigemial nerve
Lateral
Medial lemnisci

30. Blood SupplyBlood Supply

31. Thank
You