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CIRCULATORY SYSTEM OF PERIPLANETA AMERICANA
The circulatory system of periplaneta helps in the transportation of digested food, hormones etc., from one part to another in the body. Periplaneta has an open type of circulatory system as the blood, or haemolymph, flows freely within the body cavity or haemocoel. Blood vessel are poorly developed and open into spaces. Visceral organs located in the haemocoel are bathed in the blood. The three main parts associated with the blood circulatory system of periplaneta are the haemocoel ,
1.The body cavity of cockroach is filled with haemolymh or blood , hence it is called haemocoel.
2. The haemocoel is divided into three sinuses by two muscular, horizontal membranes , called
DORSAL DIAPHRAGM and
3. Both the diaphragms have pores.
4. The three sinuses of the haemocoel are known as
The doral sinus – Pericardial haemocoel ,
The middle sinus – Perivisceral haemocoel ,
The ventral sinus – Perineural haemocoel .
5.The middle sinus is very large as it contains most of the viscera.
6. The dorsal and the ventral sinuses are small as they have only heart and nerve cord , respectively.
7. There is a series of paired triangular muscles , called alary muscles. Every segment has one pair of these muscles situated on the lateral sides of the body.
8. These alary muscles are attached to the pericardial septum by their broad bases and to the terga by their pointed ends or apices.
1. Heart lies in the pericardial haemocoel or dorsal sinus.
2. It is a long, muscular , contractile tube found along the mid dorsal line, beneath the terga of the thorax and abdomen.
3. The heart consists of thirteen chambers .Three of the thirteen chambers are situated in the thorax and ten in the abdomen.
4. Every chamber opens into the other present in front of it.
5. Its posterior end is closed while the anterior end is continued forward as the anterior aorta.
6.At the posterior side of each chamber , except the last , ther is a pair of small apertures called ostis one on each side. Ostea have valves which allow the blood to pass only into the heart from the dorsal sinus.
3. BLOOD :-
1. The blood of periplaneta is colour less and is called haemolymph.
2.It consists of a fluid called plasma ,and free blood carpusclea or haemocytes , which are phagocytic .
3. Phagocytes are large in size and can ingest foreign particles such as bacteria.
4. There is no respiratory pigment in the blood and so it plays no major role in respiration.
The important functions of the blood are ;
1.It absorbs digested food from the alimentary canal and distributes it to the rest of the body.
2. It brings nitrogenous wastes from all parts of the body to the excretory organs for their elimination.
3.It carries defencive phagocytes to the places of infection where they engulf the germsand disintegrating tissue parts.
4. It transports secretions of the ductless glands to the target organs.
CIRCULATION OF BLOOD:-
1.The blood flows forward in the heart by the contractions of its chambers.
2. At the anterior end of the heart , the blood flows into the aorta and form there it enters the sinus of the head.
3. From the head sinus , the blood flows into the perivisceral and sternai sinuses .
4. On contraction of the alary muscles the pericardial septum is pulled down. This increases the volume of the pericardial sinus. Hence blood flows from the perivisceral sinus into the pericardial sinus through the apertures of the pericardial septum.
5. 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.
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