A student compares the blood system of a cockroach with that of a human…

The blood vascular system of the cockroach is open. The blood, called haemolymph, bathes the organs in the body space. A tubular heart with funnel shaped chambers and ostia pumps it forwards. The respiratory system is a network of tracheae that open through ten pairs of spiracles, two pairs in the thorax and eight in the abdomen. The tracheae branch into tracheoles that carry air to the cells. Malpighian tubules remove nitrogenous waste. The nervous system has a brain in the head and a ventral nerve cord with nine ganglia, three in the thorax and six in the abdomen. The sense organs are the antennae, the compound eyes, the palps and the anal cerci. The time for diffusion over a distance x is x squared divided by two times the diffusion constant.