The circulatory system helps in the transportation of digested food , hormones etc ., form one part to another in the body . Periplaneta has an open type of circulatory system as the blood or heamohymph, flows freely within the body cavity or heamocoel , Blood vessels are poorly developed and open into spaces Visceral organs located in the haemocoel are the heamocoel , heart and blood .
Heamocoel : The heamocoel of cockroach is divided into three sinuses by two muscular , horizontal membranes called dorsal diaphragm or pericardiat septum and ventral diaphragm . Both the diaphragms have pores . There is a series of paired triangular muscles called alary muscles .Every segment has one pair of muscles situated on the lateral sides of the body . These are attached to the pericardial septum by their broad bases and to the terga by their broad bases and to the terga by their pointed ends or apices The three sinuses of the haemocoel are known as pericardial haemocoel or the dorsal sinus, the perivisceral haemocoel or the middle sinus and sternal haemocoel or ventral sinus or perineural sinus. The middle sinus is very large as it contains most of the viscera. The dorsal and ventral sinuscs are small as they have only heart and nerve cod respectively .
Heart : The heart lies in the pericardial haemocoel or dorsal sinus . It is a long muscular , contractile tube found a long the mid dorsal line , beneath the terga of the thorax and abdomen .
lt consists of 13 chambers Every chamber opens into the other present in front of it . Three of the thirteen chambers are situated in the thorax and ten in the abdomen . Its posterior end is closed while the anterior end is continued forward as the anterior aorta . At the posterior side Ostia have valves which allow the blood to pass only into the heart from the dorsal sinus .
Blood : The blood of periplaneta is colourless and is called heamolymph . lt consists of a fluid called plasma and free blood corpuscles or haemocytes , which are phagocytic . The phagocytic , the phagocytes are large in size and can lngest foreign particles such as becteria There is no respiratory pigment in the blood and so it play no major role in respiration .
