Question

In cockroach the flow of haemolymph is:

• A. Heart $\to$ head haemocoel $\to$ perivisceral sinus $\to$ pericardial sinus $\to$ ostia $\to$ heart
• B. Heart $\to$ pericardial sinus $\to$ head haemocoel $\to$ perivisceral sinus $\to$ ostia $\to$ heart
• C. Heart $\to$ head haemocoel $\to$ perivisceral sinus $\to$ ostia pericardial sinus $\to$ heart
• D. Heart $\to$ ostia $\to$ perivisceral sinus $\to$ pericardial sinus $\to$ head haemocoel $\to$ heart

Answer 1

The correct option is A Heart $\to$ head haemocoel $\to$ perivisceral sinus $\to$ pericardial sinus $\to$ ostia $\to$ heart

• The circulation of haemolymph takes place in cockroach in the following way : The contrac­tion of alary muscles enlarges the pericardial space so that the haemolymph flows into it from the underlying perivisceral sinus. When the alary muscles relax, the haemolymph is forced through the ostia into the heart.
• As the heart relaxes during diastolethe tension of the ligament stretches out the walls of heart so that the haemolymph flows into the organs; anteriorly into the head.
  
• It then passes back from the haemocoel of head into that of the thorax and abdomen and enters the pericardium. In addition to alary muscles, contraction of dorsal diaphragm also helps in rapid circulation of haemo­lymph.
  

So, the correct option is 'Heart → head haemocoel → perivisceral sinus → pericardial sinus → ostia → heart'.