Pons in latin, refers to a “bridge”. Pons varolli is a part of brain-stem, that links thalamus with medulla oblongata. The cross-section of pons is similar to the midbrain as described earlier but few things must be kept in mind:
- The orientation of lemnisci in midbrain is more or less vertical, but in pons it is horizontal.
- Cranial nerve III and IV arises from midbrain and mainly Cranial nerve V, VI, VIII and VIII arises from pons.
- Cerebral aqueduct lies in midbrain and 4th ventricle lies in pons.
Earlier, we imagined transverse section of the midbrain as an inverted striped face of red-eyed demon. Similary, we will use the analogy of an “inverted face of a human” to draw the cross-section of pons.
Now, let’s label the structures shown above:
- Hair = Transverse pontine fibers
- Eye = Corticospinal and Corticonuclear tracts
- Ear = Middle cerebellar peduncle
- Stripes = Lemnisci
- Medially: Medial lemniscus
- Middle: Trigeminal lemniscus medially and Spinal lemniscus laterally
- Lateral: Lateral lemniscus
- Bridge of nose = Raphe nucleii
- Ala of nose = Medial Longitudinal Fasciculus
- Mole = Facial nerve motor nucleus (In caudal pons)
- Moustache = Cranial nerve nucleii
- Medial most = CN VI or Abducens nerve (In caudal pons)
- Middle = CN V or Trigeminal nerve – motor and sensory (In rostral pons)
- Lateral most = CN VIII – Superior vestibular nucleus (In caudal pons)
- Lips = Periventricular gray
- Contains locus coeruleus
- Open mouth = 4th ventricle
- Chin = Superior cerebellar peduncle
Now, let’s look at the real picture:
You can compare with your own face to learn the pons. Wasn’t that easy? Leave comments below 🙂 .