![](/drem/stage22/labels2/S205L.gif)
![alar plate of mesencephalon, alar plate of metencephalon (cerebellum), cerebral aqueduct (mesocoele), commissure of superior colliculus, intermediate zone, isthmus of rhombencephalon, marginal zone, rhombencoel (fourth ventricle), roof plate, trochlear nerve decussation, ventricular zone](/drem/stage22/Z0/S205N.jpg)
![](/drem/rulerbg.png)
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Boyd Embryo #H983 | Location: 18-1-1
Keywords: alar plate of mesencephalon, alar plate of metencephalon (cerebellum), cerebral aqueduct (mesocoele), commissure of superior colliculus, intermediate zone, isthmus of rhombencephalon, marginal zone, rhombencoel (fourth ventricle), roof plate, trochlear nerve decussation, ventricular zone
Source: The Virtual Human Embryo.