Final answer:
Epithelial-like cells called pinacocytes line the inner chamber of sponges, forming the protective pinacoderm, and include porocytes which regulate water flow into the spongocoel.
Step-by-step explanation:
The type of cell that lines the inner chamber of sponges is epithelial-like cells, specifically called pinacocytes. These cells form the innermost layer, known as the pinacoderm, and play a role similar to our epidermis by serving a protective function. Unlike true epithelial cells that cover the body surfaces of higher animals and line their internal cavities, sponge cells do not form true tissues. However, the pinacoderm serves as a barrier and includes specialized cells such as porocytes, which regulate the flow of water into the sponge's central cavity, the spongocoel. Sponges also contain other cell types, including amoebocytes and sclerocytes, within a jelly-like substance called the mesohyl that acts like an endoskeleton to maintain the sponge's structure.