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Chapter 3 (page 16)
Sphincteric mechanism at pylorus
In view of the muscular build of the distal stomach it appears unlikely that the pyloric
ring as such, constitutes a sphincter in the usually accepted sense of the word. According
to Torgersen (l942) the sphincteric mechanism at the pylorus is more intricate; it
involves the various divisions of the musculature of the sphincteric cylinder as described
above, the fibrous septum separating the circular musculature of the cylinder from that of
the duodenum, and the circular musculature surrounding the commencement of the
duodenum. In other words, it consists of gastric and duodenal divisions.
It seems to us that like the Roman God of the Gates, Janus
(Latin janua: gates), the pyloric sphincteric cylinder acts as a
keeper of entrances and exits. It is orientated backwards (i.e. orally) as well
as forwards (i.e. caudally). It has to receive swallowed liquids and solids,
accomodate and prepare them for as long as necessary, and deliver them into
the duodenum. It appears that it may play an important role, not only in gastric
emptying of solids and liquids, but also in various aspects of gastro-duodenal
The pyloric sphincteric cylinder is the same muscular structure as the canalis egestorius
and the fan-shaped muscle. It is suggested that the terms right and left pyloric loops be
used for right and left canalis loops respectively. For muscle torus the term muscle knot is preferred as the two loops meet in that situation.
Pyloric ring is the fold (consisting of muscular and mucosal/submucosal
components) separating the lumen of the stomach from that of the duodenum.
Pyloric aperture is the opening surrounded by the lips of the pyloric
ring. Its diameter varies, depending mainly on the degree of contraction and
relaxation of the cylinder.
Pyloric canal is the contracted pyloric sphincteric cylinder; it is 2.0 to 3.0 cm in length in adults.
- Cole LG. The living stomach and its motor phenomenon. Acta Rad l928, 9, 533-
- Cunningham DJ. The varying form of the stomach in man and the anthropoid
ape. Trans Roy Soc Edinb l906, 45, 9-47.
- Forssell G. Über die Beziehung der Röntgenbilder des menschlichen Magens zu
seinem anatomischen Bau. Fortschr Geb Röntgenstr l913, Suppl 30, 1-265.
- Horton BT. Pyloric musculature with special reference to pyloric block. Amer J
Anat l928, 41, l97-225.
- Keet AD, Heydenrych JJ. The anatomy and movements of the pyloric sphincteric
cylinder. South Afr Med J l982, 62, 15-18.
- McNaught GHD. Simple pyloric hypertrophy in the adult. J Roy Coll Surg Edin
l957, 3, 35-41.
- Pernkopf E. Die Entwicklung der Form des Magendarmkanals beim Menschen.
Zeitschr gesam Anat l921, 64, 96-275.
- Pernkopf E. Idem. Ibid. l924, 73, 1-144.
- Torgersen J. The muscular build and movements of the stomach and duodenal
bulb. Acta Rad l942, Suppl 45, l-l9l.
- Torgersen J. The developmental anatomy of the pyloric canal and the etiology of
infantile pyloric stenosis. Acta Rad l949, 32, 435-438.
- Welch EH. Development of the musculature of the stomach with special
reference to its condition in the newborn child and the premature infant. Papers from
Mayo Foundation and Medical School Univ Minnesota l921 - l922, 2, 3-23.
- Williams I. Closure of the pylorus. Brit J Rad l962, 35, 653-670.
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