The cell to cell communication is a characteristic feature of the multicellular organism which takes place through the special junctions.
The epithelium is a layer of animal cell therefore the junction which allows the passage of small molecules from one cell to another cell is known as Gap junction.
Gap junctions are formed by the arrangement of connexon proteins in the membrane which allows the molecules smaller than the 1000 Da to move between the cells.
you can find the volume of an irregular object by immersing it in water in a beaker (or other container) with volume marks and see how much the level goes up.
