The body of the cockroach is divided into three sinuses. Pericardial on the dorsal side, perineural on the ventral side and perivisceral in the center. Two diaphragms separate these three sinuses. The ventral diaphragm is between perivisceral and perineural sinuses and the dorsal diaphragm is between pericardial and perivisceral sinuses. There is ostia present, which acts as communication between these sinuses.