Describe the process of blood circulation in Periplaneta .

Explanation

The blood flows forward in the heart by the contractions of its chambers . At the anterior end of the heart , the blood flows into the aorta and from there it enters the sinus of the head From the head sinus , the blood flows into the perivisceral and sternal sinuses . On contraction of the alary muscles the pericardial septum is pulled down . This increases the volume of the pericadial sinus . Hence blood flows from the perivisceral sinus into pericardial sinus through the appertures of the pericardial septum . On relaxation of the alary muscles , the pericardial septum moves upwards to its original position . This forces the blood , to enter the chambers of the heart through the ostia from the pericardial sinus .