Final answer:
Tight junctions, also known as occluding junctions or zonula occludens, create a watertight seal between adjacent animal cells by preventing the movement of extracellular fluids between cells. These structures are found in sheets of epithelial cells that line the lumens of organs.
Step-by-step explanation:
Tight junctions, also known as occluding junctions or zonula occludens, are structures found in sheets of epithelial cells that line the lumens of organs. They create a watertight seal between adjacent animal cells, preventing extracellular fluids from crossing between cells. This barrier is formed by tight junction membrane proteins (TJMPs), which hold the cells together and create a waterproof barrier.