Lifeblood flow: The circulatory systems

Abstract

The function of the circulatory system (CS) is transport for supply of nutrients like amino acids, vitamins or electrolytes, gases, hormones, and blood cells; removal of toxic agents and metabolic products; and regulation of body temperature and volume. In some animals like flatworm or jellyfish, the CS is absent. In these animals every cell is able to obtain nutrients/water and oxygen without the need of the transport system.