at one face of the Golgi stack, the convex cis-face (entry or forming
internalize ligands bound to surface receptor molecules and is also
surface). Here, they deliver their contents to the first cisterna in the
termed receptor-mediated endocytosis. Caveolae (little caves) are struc-
series by membrane fusion. From the edges of this cisterna, the protein
turally distinct pinocytotic vesicles most widely used by endothelial and
is transported to the next cisterna by vesicular budding and then
smooth muscle cells, when they are involved in transcytosis, signal
fusion, and this process is repeated across medial cisternae until the
transduction and possibly other functions. In addition to late endo-
final cisterna at the concave trans-face (exit or condensing surface) is
somes, lysosomes can also fuse with phagosomes, autophagosomes
reached. Here, larger vesicles are formed for delivery to other parts of
and plasma membrane patches for membrane repair. Lysosomal hydro-
the cell.
lases process or degrade exogenous materials (phagocytosis or hetero-