Go to chapter: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39
Chapter 11 (page 44)
Anatomy of the Pyloric Ring
In fresh specimens a narrow (3.0mm to 4.0 mm) annular thickening, the pyloric ring,
is felt in the wall of the gut at the gastro-duodenal junction. At laparotomy it may be
difficult to palpate (Edwards and Rowlands l968), due to the effects of muscle
relaxants administered during anaesthesia. On radiographs taken during the motor
quiescent phase of the interdigestive myoelectric complex, the ring presents as a deep,
clearcut, annular indentation separating the barium in the lumen of the stomach from
that in the duodenum (Fig 11.1).
|Fig. 11.1. Radiograph of normal
pyloric ring (arrow) in motor quiescent phase of interdigestive myoelectric complex
Edwards (l96l) found the length of the ring, as measured on radiographs, to vary
between 1.0mm and 12.0mm; the mean length was 1.7mm. It was not stated whether
these measurements were taken during motor quiescent or during contraction phases.
(Comment: the term "width" is preferred to "length" as used by Edwards. Normally,
the width of the pyloric ring may vary, depending on the stage of contraction of the
pyloric sphincteric cylinder, as described in Chapter 13).
The width and height of the pyloric ring, and the diameters of the pyloric aperture,
sphincteric cylinder and duodenal bulb, were measured on radiographs of 10 adult
subjects, taken at a time when no visible motor activity was evident, i.e. during the
motor quiescent phase of the interdigestive myoelectric complex (Fig 11.2, Table
11.1). All subjects had been referred for radiographic examination because of vague
upper abdominal symptoms. In none could an organic lesion be demonstrated;
clinically and radiologically the stomach and duodenum were considered to be normal
in all. The mean width of the ring was 4.7mm and the mean height 11.1mm; the
depth was approximately the same on the greater and lesser curvature sides.
|Fig. 11.2. Diagram of
pyloric ring in motor quiescent phase. W, width; H, height; DB, duodenal bulb; PA, pyloric
aperture; PSC, pyloric sphicteric cylinder|
The inner margin of the ring surrounds the pyloric aperture, i.e. the opening by which
the lumen of the stomach communicates with that of the duodenum. In the motor
quiescent phase the diameter of the aperture varied from 5.0 to 13.0mm, with a mean
of 8.7mm. The mean diameter of the sphincteric cylinder was 57.1mm, and the mean
diameter of the duodenal bulb 35.8mm. (Comment: Owing to magnification factors
the real measurements will be approximately four-fifths of the figures given).
Table 11.1 Radiographic measurements during the motor quiescent phase of the
It is concluded that the pyloric ring causes an appreciable constriction of the lumen at
the gastroduodenal junction. Furthermore it is seen that the pyloric aperture is patent
during the motor quiescent phase.
|Case||Width of ring (mm)||Height of ring (mm)||Diameter Aperture
||Diameter sphincteric cylinder (mm)||Diameter duodenal bulb (mm)|
Previous Page | Table of Contents | Next Page
© Copyright PLiG 1998