Question

The three sinuses in a cockroach are not equal in size. Why? (U)

Answer 1

There are three sinuses in the cockroach that contain haemolymph. The haemocoel i.e. the body cavity is divided into three sinuses (Dorsal-Pericardial haemocoel, middle- Perivisceral haemocoel and ventral- Perineural haemocoel) by two muscular horizontal membranes; dorsal diaphragm and ventral diaphragm. Dorsal sinus contains heart and ventral sinus contains nerve cord are smaller as compare to the middle larger sinus containing most of the viscera.