Sponges contain an outer wall covered by flat cells called pinacocytes as well as pores surrounded by special cells called porocytes. Their internal wall is filled with choanocytes, flagellate cells specialized in the phagocytosis of food brought to the central cavity. The choanocyte flagella also maintain the water flow inside the sponge.
Between the outer and the inner sections of the body of a poriferan, there are cells with amoeboid movement (via pseudopods) called amoebocytes. Since they are embedded in connective tissue, amoebocytes move and distribute nutrients to other cells as well as produce spicules that fill the tissue and support the body structure like a primitive skeleton. (Some poriferans have an internal skeleton, which is an endoskeleton, made of spicules and organic fibers.)