Cardiac glands are limited to a narrow region of the stomach (the cardia) that surrounds the esophageal orifice. Their secretion, in combination with that of the esophageal cardiac glands, contributes to the gastric juice and helps protect the esophageal epithelium against gastric reflux. The glands are tubular, somewhat tortuous, and occasionally branched (Fig. 17.14 and Plate 56, page 610). They are composed mainly of mucus-secreting cells, with occasional interspersed enteroendocrine cells. The mucus-secreting cells are similar in appearance to the cells of the esophageal cardiac glands. They have a flattened basal nucleus, and the apical cytoplasm is typically filled with mucin granules. A short duct segment containing columnar cells with elongate nuclei is interposed between the secretory portion of the gland and the shallow pits into which the glands secrete. The duct segment is the site at which the surface mucous cells and the gland cells are produced.
FIGURE 17.13 • Gastrointestinal hormones. This schematic diagram shows the distribution of gastrointestinal peptide hormones produced by enteroendocrine cells in the alimentary canal. CCK, cholecystokinin; VIP, vasoactive intestinal peptide; GIP, gastric inhibitory peptide. (Modified from Johnson LR, ed. Gastrointestinal Physiology. St. Louis: Mosby-Year Book, 1997.)
Pyloric Glands of the Gastric Mucosa
Pyloric gland cells are similar to surface mucous cells and help protect the pyloric mucosa.
Pyloric glands are located in the pyloric antrum (the part of the stomach between the fundus and the pylorus). They are branched, coiled, tubular glands (Plate 58, page 614).
583 TABLE Physiologic Actions of Gastrointestinal Hormones 17.1 Major Action Hormone Site of Synthesis Stimulates Inhibits Gastrin G cells in stomach Gastric acid secretion Ghrelin Gr cells in stomach GH secretion Appetite and perception of hunger Lipid metabolism Fat utilization in adipose tissue Cholecystokinin (CCK) I cells in duodenum and jejunum Gallbladder contraction Pancreatic enzyme secretion Pancreatic bicarbonate ion secretion Pancreatic growth Gastric emptying Secretin S cells in duodenum Pancreatic enzyme secretion Pancreatic bicarbonate ion secretion Pancreatic growth Gastric acid secretion Gastric inhibitory peptide (GIP) K cells in duodenum and jejunum Insulin release Gastric acid secretion Motilin Mo cells in duodenum and jejunum Gastric motility Intestinal motility Modified from Johnson LR, ed. Essential Medical Physiology. Philadelphia: Lippincott-Raven, 1998. GH, growth hormone.