In the vertebrate embryo, a rhombomere is a segment of the developing rhombencephalon. The rhombomeres appear as a series of swellings. The mature rhombencephalon is composed of the pons, cerebellum and medulla.

Cells from each rhombomere can mix with each other but can't mix with cells from other rhombomeres. Neural crest cells from each rhombomere give rise to different ganglia, or clusters of neurons. The fate of a rhombomere is affected by differential expression of Hox genes.

Embryology