Origin and migratory pathways of the eleven epithelial cell types present in the body of the mouse stomach.

The secretions of the mammalian stomach are produced by cells present in invaginations of the epithelium, which in the mouse are straight tubules referred to as "zymogenic units." These units comprise four regions, namely pit, isthmus, neck, and base, in which there are several cell lineages with different phenotypes and migratory pathways. In the isthmus, stem cells designated "undifferentiated granule-free cells" undergo division so as to maintain their own number and produce several differently oriented progenitors: (1) "Pre-pit cell precursors" are characterized by prosecretory Golgi vesicles with a uniform, fine particulate content. They give rise to "pre-pit cells" defined by the presence of few dense mucous granules. These cells migrate outward from the isthmus to the pit, where they become the dense granule-rich "pit cells" which populate the pit region and migrate to the gastric surface where they are lost. (2) "Pre-neck cell precursors" are identified by prosecretory Golgi vesicles containing an irregular dense center and a light rim. They give rise to "pre-neck cells" defined by a few mucous secretory granules with a clear-cut core. These cells migrate inward from the isthmus to the neck where they become "neck cells," which contain many such granules. Even though neck cells are mature mucus-producers, they are not end cells. As they enter the base region, they become "prezymogenic cells" whose phenotype gradually changes from mucous to serous. These cells eventually lose the ability to produce mucus and thus become the typical zymogenic cells that populate the base region. (3) "Pre-parietal cells" are classified into three variants, which probably come from three different sources, that is, pre-pit cell precursors, pre-neck precursors, and the undifferentiated granule-free cells themselves. The preparietal cells mature into parietal cells which migrate either outward to the pit or inward to the neck and base. As a result, parietal cells are scattered in the four regions of the unit. (4) Precursors of "entero-endocrine" and "caveolated" cells give rise in the isthmus to these cells, which may also migrate outward or inward.