abnormal motile primary cilium physiology absent nodal flow absence of the leftward movement of extra-embryonic fluid at the ventral node; nodal flow is autonomously generated by the rotation of cilia that are tilted toward the posterior on cells of the ventral node and is the central process in symmetry breaking on the left-right axis; when nodal cilia are immotile or absent, nodal flow does not occur MPheno.ontology csmith MP:0012093 2013-09-23T11:05:41Z