Final answer:
Large substances exit capillaries through transcytosis, which involves the engulfing and releasing of substances via vesicles, distinct from other processes like facilitated diffusion.
Step-by-step explanation:
The method by which large substances can cross endothelial cells and exit a capillary is through transcytosis. Transcytosis combines endocytosis, where substances are engulfed by the cell membrane into vesicles, and exocytosis, where substances are released out of the cell. It differs from other forms of membrane transport such as simple diffusion, where small hydrophobic molecules are transported, osmosis, which is specific to water molecules, and facilitated diffusion, which involves transport proteins for larger molecules but does not involve engulfing substances into vesicles.