The pons is part of the brainstem located inferior to the midbrain and superior to the medulla oblongata. It has anterior and posterior surfaces. Notable features on the anterior surface include the emergence of the trigeminal nerve and the abducent, facial, and vestibulocochlear nerves between the pons and medulla. The internal structure of the pons contains basal and tegmental parts, which can be seen on transverse sections passing through the caudal and cranial parts. Key structures visible in these sections include cranial nerve nuclei, fiber tracts such as the medial lemniscus, and pontine nuclei.

1. Pons
The pons is part of the brainstem, and in humans it lies inferior to
the midbrain, superior to the medulla oblongata and anterior to
the cerebellu

2. Gross Features of Pons
Anterior Surface
1. Its is convex from side to side and
shows many transvers fibers that
converge in the center forming middle
cerebellar peduncle.
2. There is shallow groove in the midline
known as the Basilar groove
3. On the anterolateral surface the
Trigeminal nerve emerges . Its has two
parts a smaller and medial motor part
and a large and lateral sensory part .
4. In the groove between pons and m.o
from lateral to medial , the abducent
,facial and vestibulocochlear nerve
appear.

3. 1. Its hidden by the cerebellum
2. It forms upper half of the floor of the fourth ventricle
3. It is limited laterally by superior cerebellar peduncles
.
4. It is divided into symmetrical halves by median sulcus
.
5. Lateral to this sulcus is an elevation known as medial
eminence , which is bound laterally by sulcus
limitans .
6. Thw inferior end is expanded to form the facial
colliculus .
7. The floor of the superior part of sulcus limitans is
bluish gray in color and is called substantia
ferruginea
8. Lateral to the S.L is the vestibuli produced by
underlying vestibular nuclei
Posterior surface

4. Internal structure of pons
• The pons is commonly divided into
1. Anterior basal part
2. Posterior tegmental part
• The structure of pons is studied at two levels
1. Transverse section through caudal part passing the facial colliculus .
2. Transverse section through the cranial part passing the trigeminal nuclei .

5. Transverse section through the caudal part

6. Important points regarding caudal T.S
The following are some important structures visible at caudal level of t.s (tegmental part)
• Medial lemniscus
• Facial nucleus
• Medial longitudinal fasciculus
• Medial vestibular nucleus
• Spinal nucleus of trigeminal nerve
• Trapezoid body
Basilar part of the pons contain the following structures
• Small mass of nerve cells known as pontine nuclei (corticopontine fibers of crus cerebri terminate here)
The axons of these cells give origin to transverse fibers which cross the midline.

7. Transverse section through the cranial part

8. Important points regarding cranial T.S
It is similar to the cranial part of the pons except for the following
structures
• Motor nucleus of the trigeminal nerve
• Principal sensory nucleus of the trigeminal nerve
• Superior cerebellar peduncle
• The lateral and spinal lemnisci lie at the lateral extremity.