Process of blood circulation

Circulation of blood takes place in two phases due to the action of the alary muscles as well as the muscles of the walls of the heart.

The two phases are

1. Diastole: During which expansion of heart takes place.
2. Systole: Contraction of heart takes place

Diastole:

• Expansion of heart (diastole) occurs due to contraction of tergum.
• It results in increase of volume of heart and decrease in the area of pericardial sinus.
• This creates a pressure on the blood in pericardial sinus forcing the blood to enter into the heart through the incurrent ostia.
• These incurrent ostia allow only the entry of blood from the sinus in to the heart and prevents its backflow from the heart to the sinus.

Systole:

• Contraction of heart (systole), is brought about by the expansion of the alary muscles as well as contraction of the muscles of the heart wall.
• This creates pressure on the blood within the heart leading to its forward movement into the aorta.
• From the aorta, blood enter into the head and flows back bathing the visceral organs in the visceral sinus and neural cord in the perineural sinus.

In between diastole and systole there will be a short period of rest which is known as diastasis. Blood flow to the posterior part of the body and into the pericardial sinus, due to the undulating movements of the dorsal and ventral diaphragms.During the process of circulation throughout the body some part of the blood flows into the accessory pulsatile organ that are present at the base of appendages like legs, wings and antennae.