[2] The floor (i.e. the anterior edge) of the fourth ventricle constitutes the rhomboid fossa, and comprises a number of general features.

The medulla oblongata is located behind the inferior portion of the floor (and continues caudally of the ventricle).

Medullary striae emerge via the median sulcus and run transversely across the floor to become part of the inferior cerebellar peduncle.

The ventricular system including the fourth ventricle, develops from the central canal of the neural tube.

Specifically, the fourth ventricle originates from the portion of the tube that is present in the developing rhombencephalon.

[3] During the first trimester of pregnancy the central canal expands into the lateral, third and fourth ventricles, connected by thinner channels.