Histological
anatomy of the stomach and duodenum
Stomach
The gastric epithelial cells are mucous
producing and are turned over rapidly. In the pyloric part of the stomach and
also the duodenum mucus-secreting glands are found. Most of the specialised
cells of the stomach (parietal and chief cells) are found in the gastric crypts
(Fig. 51.3). The stomach is also richly endowed with endocrine cells.
Parietal cells
These are in the body (acid-secreting portion)
of the stomach and line the gastric crypts, more abundant distally. These are
responsible for the production of hydrogen ions to form hydrochloric acid, which
has a pH of around 1. The hydrogen ions are actively pumped by the proton
pump, a hydrogen—potassium APTase (Sachs) which exchanges intraluminal
Chief cells
These lie principally proximally in the
gastric crypts and produce pepsinogen. Two forms of pepsinogen are described:
Endocrine cells
The stomach is richly endowed with endocrine
cells, which are critical to its function. In the gastric antrum the mucosa
contains G cells which produce gastrin. Throughout the body of the stomach
enterochromatin-like (ECL) cells are abundant and produce histamine, a key
factor in gastric acid secretion. In addition, there are large numbers of
somatostatin-producing
D cells throughout the stomach, and somatostatin has a negative regulatory role.
The peptides and neuropeptides produced in the stomach are discussed later.
Duodenum
The duodenum is lined by a mucus-secreting
columnar epithelium. In addition, Brunner’s glands lie beneath the mucosa and
are similar to the pyloric glands in the pyloric part of the stomach. Endocrine
cells in duodenum produce cholecystokinin and secretin.