The lobster's circulatory system is fairly simple compared to most organisms. It consists of a single chambered heart made up of striated muscle and small openings called ostia. The pericardium, or percardinal sinus, suspends the heart directly above the foregut (pyloric stomach). Lobster blood, referred to as hemolymph, begins by entering the pericardium, then enters the ostia where it finally ends up in the heart.To create the flow of blood, ostia valves close building up pressure in the pericardium, which opens the exit valves(cardioarterial valves) so that the heart can empty. The blood is then fed into arteries that feed int the abdomen and to the frontal sensory organs.