“extra-cellular fluid” is literally just all the water outside the cells. Put a cell in a bowl of water, and the water is the extra-cellular fluid. Suspend the cell in a human-shaped bag of water (which is what a human is) and the extra-cellular fluid is the water that isn’t inside any of the cells.
Cell membranes work in the exact same way the whole oil in water thing does, only where oil forms “solid” bubbles that are oil all the way through, phospholipids form a thin layer that traps some of the water inside it. That trapped water is the cytoplasm.
Latest Answers