Porocytes are tubular cells which make up the pores of a sponge. Covering the sponge's a layer of cells, very similar to skin, but it's slightly different. To scientists, these cells are known as pinacocytes. In a sponge, pinacocytes are a thin, elastic layer which keeps water out. Between the pinacocytes, there're the porocytes. These let water into the sponge. Myocytes, little muscular cells, open up the porocytes and close them. Once through the pores, water travels down canals. Using the foo… (More on Porocytes)