Question

where are ostia and sinuses present in cockroach?

Answer 1

Each chamber of heart in the cockroach receives oxygenated blood by a slit-like opening known as ostia. The valve present in ostia prevents the backflow of blood.
The large body cavity or haemocoel is divided by double membranous partitions into three wide and flattened structures known as sinuses.
Pericardial sinus contains heart. Perivisceral sinus containing gut and perineural sinus containing nerve cord.