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normal circulation the blood is pumped forwards through the heart at systole, passing out of the heart via the excurrent ostia and, anteriorly, from the aorta.The dorsal diaphragm is usually convex above so that contraction of the alary muscles tends to flatten it. This flattening increases the volume of the pericardial sinus at the expense of the perivisceral sinus so that this causes a flow of blood up into the pericardial sinus, and then into the heart at diastole through the incurrent ostia.Blood percolates down to the perineural sinus where it is agitated by movements of the ventral diaphragm which assist the blood flow to the nerve cord and possibly produce a backward flow of blood.

normal circulation the blood is pumped forwards through the heart at systole, passing out of the heart via the excurrent ostia and, anteriorly, from the aorta. The blood driven forward by the heart increases the pressure anteriorly in the perivisceral sinus so that in this sinus the blood tends to flow posteriorly along a pressure gradient. Blood percolates down to the perineural sinus where it is agitated by movements of the ventral diaphragm which assist the blood flow to the nerve cord and possibly produce a backward flow of blood. The dorsal diaphragm is usually convex above so that contraction of the alary muscles tends to flatten it. This flattening increases the volume of the pericardial sinus at the expense of the perivisceral sinus so that this causes a flow of blood up into the pericardial sinus, and then into the heart at diastole through the incurrent ostia.
• In general, the flow through the wings is outward through the anterior veins and then inward through the posterior veins. The passage from anterior veins to posterior veins is via the cross veins. The blood flows from the posterior veins back into the body via the axillary cord.
•The pulsatile organs help the flow of blood through the antennae and in the Heteroptera the legs. Most insects have a longitudinal septa dividing the legs into an anterior and a posterior channel. In most insects the blood flows outward through the posterior channel and inward through the anterior channel.