has part has part has_part characteristic of part of has modifier abnormal medulla oblongata morphology abnormal retrotrapezoid nucleus morphology MP:0011406 2011-10-31T04:13:24Z any structural anomaly in the loose collection of neurons that reside in the rostral medulla close to the medullary surface, ventral and immediately caudal of nVII, that are crucial for CO2 sensing in the brain MPheno.ontology csmith morphology abnormal retrotrapezoid nucleus