part of open tracheal system development regulation of tube size regulation of tube size, open tracheal system Ensuring that an epithelial tube in an open tracheal system is of the correct length and diameter. Tracheal tubes undergo highly regulated tube-size increases during development, expanding up to 40 times their initial size by the end of larval life. Tube size appears to be controlled by regulation of apical membrane expansion and secretion, rather than by changes in cell number, size or shape. regulation of tracheal tube size biological_process GO:0035151 regulation of tube architecture, open tracheal system