how sponges rely on water moving through their bodies for respiration.

The gel-like consistency of mesohyl acts like an endoskeleton and maintains the tubular morphology of sponges.

Mesohyl is an extracellular matrix consisting of a collagen-like gel with suspended cells that perform various functions. Pinacocytes, which are epithelial-like cells, form the outermost layer of sponges and enclose a jelly-like substance called mesohyl. While sponges (excluding the hexactinellids) do not exhibit tissue-layer organization, they do have different cell types that perform distinct functions. However, sponges exhibit a range of diversity in body forms, including variations in the size of the spongocoel, the number of osculi, and where the cells that filter food from the water are located. Water entering the spongocoel is extruded via a large common opening called the osculum. Water can enter into the spongocoel from numerous pores in the body wall.

The morphology of the simplest sponges takes the shape of a cylinder with a large central cavity, the spongocoel, occupying the inside of the cylinder.

How sponges rely on water moving through their bodies for respiration.