GENERAL HISTOLOGY

Detailed explanation-1: -How do sponges feed? They draw water into central cavity by collar cells; as it passes through the sponge walls, amoebocytes pick up nutrients from the water. The water then exists through oscula.

Detailed explanation-2: -Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues and organs. Some of them are radially symmetrical, but most are asymmetrical.

Detailed explanation-3: -In addition to the osculum, sponges have multiple pores called ostia on their bodies that allow water to enter the sponge. In some sponges, ostia are formed by porocytes, single tube-shaped cells that act as valves to regulate the flow of water into the spongocoel.

Detailed explanation-4: -Water enters the sponge through a series of incurrent canals and passes through internal pores called prosopyles into the radial canals, which are lined with flagellated collar cells known as choanocytes. It is the action of these choanocytes that keeps water moving through the sponge.