The mature stomach. Still pumping out acid?
Feldman
M
M
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005744:Gastric Acid / Q000378:metabolism*; D005757:Gastritis, Atrophic / Q000453:epidemiology*; D006801:Humans