gastric juice: the digestive secretion of the gastric glands of the stomach. glands: cells or groups of cells that secrete materials for special uses in the body. Glands may be exocrine (EKS-oh-crin) glands, secreting their materials “out” (into the digestive tract or onto thesurface of the skin), or endocrine (EN-doe-crin) glands, secreting their materials “in”(into the blood).