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Chapter 5 (page 24)
The mucosal folds in the pyloric region can be demonstrated readily in the intact, living
human stomach by radiographic techniques. Swallowing a few mouthfulls of a suitable
barium sulphate suspension on the empty stomach, and applying graduated compression
on the anterior abdominal wall, shows the folds to advantage (Chap. 13). By means of
image intensification and TV monitoring the movements of the mucosal folds may be
studied (Chap. 13).
The size of the folds is determined by the volume of the submucosa (Forssell l923, l934)
and degree of distension of the lumen; increasing luminal distension causes progressive
effacement of the folds. A similar but more pronounced effect is seen when contraction
of the muscularis externa is abolished by the administration of anticholinergic substances,
and simultaneous distension of the lumen obtained by means of air or gas insufflation.
Under these circumstances macroscopic folds may disappear altogether. This principle is
utilized in the upper gastrointestinal double contrast radiographic examination.
The position or direction of the mucosal folds during life depends mainly on the degree
of contraction or relaxation of the muscularis externa. In his epic studies Forssell (l923,
l934, l939) demonstrated "independent but co-ordinated" contractions of the muscularis
externa and mucosa (brought about by contractions of the muscularis mucosae). One of
the best examples of this phenomenon is seen during contraction of the pyloric
sphincteric cylinder. Normally, when the cylinder is relaxed, its mucosal folds are
circular; during contraction the folds change in direction, and with maximal contraction
only longitudinal folds are seen in the fully contracted cylinder (Chap. 13).
When examining the surface of the gastric mucosa with a magnifying lens in the fresh
specimen, it is seen to be divided into a multitude of small, slightly elevated polygonal
areas by numerous linear depressions. These raised areas, which measure from 1.0 to 6.0
mm in diameter, are called the areae gastricae. On the surface of the areae gastricae
numerous small tubular invaginations, the gastric pits or foveolae, are seen. It is into the
bottom of these pits that the gastric glands open. Double contrast radiographic
examination demonstrates the areae gastricae (Chap. 13). They are seldom visible
endoscopically (Mcintosh and Kreel l977).
The mucous membrane of the first part of the duodenum, unlike that of the stomach,
usually appears smooth, but on close inspection is seen to be thrown into rudimentary
folds. Grossly visible crescentic mucosal folds (plicae circulares or valves of Kerckring)
commence 2.5 to 5.0 cm distal to the pylorus, extending half to two-thirds of the way
around the lumen.
Two anatomico-functional divisions of the pyloric part of the stomach are clearly
identifiable. The first, the muscular pyloric sphincteric cylinder, is a tube of thickened
muscularis externa, approximately 3.0 to 5.0 cm in length when fully contracted (in
adults). It is definable in morbid anatomical specimens, in which it is seen to end in an
aboral thickening, the pyloric sphincteric ring (which forms the peripheral part of the
pyloric ring) (Chap. 3, 11). The pyloric sphincteric cylinder is also clearly definable in
radiographic motility studies during life (Chap. 13).
The second anatomico-functional entity in the distal stomach is the pyloric mucosal zone,
containing mucus secreting and neuroendocrine cells. (Radiologically there are no
differentiating features between the various mucosal zones). Unlike the cylinder, the
mucosal zone may vary in extent in pathological conditions.
Anatomically the pyloric mucosal zone differs from the sphincteric cylinder in extent as
well as in shape. In the normal stomach the mucosal zone is longer than the cylinder,
especially on the lesser curvature. While the cylinder is roughly triangular in shape or
fan-shaped, with the apex on the lesser and the base on the greater curvature (when
contracted), the greatest length of the mucosal zone occurs on the lesser curvature (Fig.
The entire sphincteric cylinder is lined by pyloric mucosa. Aborally both the mucosal
zone and the cylinder end at the pyloric ring. At the oral end of the cylinder pyloric
mucosa extends into the more proximal part of the stomach.
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