A section through the dorsal part of the mes- and metencephalon junction.
Observe:
1. The rootlets of the trochlear nerve arising from the junction area.
2. The thin roof of the fourth ventricle joining the alar plate of the metencephalon.
Keywords: alar plate(s), junction of mesencephalon and metencephalon, mesocoele (midbrain ventricle), metencephalon, middle cerebral plexus, rhombencoel (fourth ventricle), roof of rhombencoel (fourth ventricle), tectum of mesencephalon (midbrain), trochlear nerve rootlets (CN IV)
Source: Atlas of Human Embryos.