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Chapter 13 (page 55)
In a consideration of motility patterns of the distal 3.0 to 4.0 cm of the stomach, it is
necessary to determine if gastric peristaltic waves normally proceed as far as the pyloric
Golden (l937) stated that each narrow peristaltic wave proceeding down the stomach
terminated in "antral systole", i.e. a segmental or concentric contraction of the entire
canalis egestorius described by Forssell (l913), which corresponds to the pyloric
Other authors differed. During simultaneous cineradiographic and kymographic studies
in man, Smith et al. (l957) found that both Type I and Type II waves invariably
progressed over the antrum toward the pylorus in a peristaltic manner. In some cases the
pylorus failed to relax as barium was driven towards it (which implied that the waves
proceeded as far as the pylorus); in other cases the wave faded just proximal to the
Rhodes et al. (l966) stated that propulsive contractions arose near the incisura angularis
and progressed smoothly towards the pylorus (from which it is concluded that they
reached the pylorus).
Carlson et al. (l966), during simultaneous cineradiograpic, pressure and electrical studies
in dogs, found that Type I waves passed in a continuous, peristaltic manner to the pyloric
ring. Type II waves behaved differently; when such a wave reached a point 3.0 to 4.0
cm from the pyloric ring, the terminal segment of the antrum and the pyloric canal
contracted in a segmental, simultaneous way. The contraction, designated a terminal
antral contraction (TAC), was followed by relaxation. An antral cycle was the time from
completion of one antral contraction wave to completion of the next. The pyloric canal
almost always contracted with the terminal antrum. (Comment: Pyloric
canal was equated with the pyloric aperture). Sometimes the pyloric canal would narrow
early in the cycle but not completely close, so that movement of the contents through it
into the duodenum occurred while the "antrum" was contracting. Simultaneous
contraction of the terminal antrum and pyloric canal had an important effect on luminal
contents; when contraction occurred, most of the contents were forcefully regurgitated
into the proximal antrum (retropulsion) instead of being propelled into the duodenum
(propulsion). Thus Type II contractions had a dual action, viz. propulsion into the
duodenum and retropulsion into the stomach. Each TAC correlated with a sharp increase
in intraluminal pressure. The mean rate of TAC's was 4.8 per minute in dogs.
Carlson et al. (1966) found that over the proximal antrum a definite interval always
occurred between the detection of basal electrical rhythm (BER) at successively distal
electrodes. As the BER complex reached the terminal antrum, its rate of conduction
increased several fold and it was detected simultaneously, or nearly simultaneously, at
successive electrodes, providing the pattern for TAC. The pyloric canal was closed
during TAC and the rest phase following on TAC; it was open during peristalsis before
the onset of TAC.
Edwards and Rowlands (l968) described Type I waves as shallow, annular, moving
constrictions that progressed along the body of the stomach towards the pylorus. Type II
waves were a deeper version of the former. As these constrictions approached the distal
4.0 cm of the stomach, instead of continuing in a sequential manner to the pylorus, they
ended in a simultaneous, concentric contraction of the entire 4.0 cm long segment.
According to Code and Carlson (l968) three patterns of peristaltic activity are to be
observed in this region: (1) some peristaltic contractions diminish in amplitude as they
progress into the terminal antrum, where they simply fade away; (2) some contractions
pass with increasing vigour over the entire antrum to end abruptly at the pylorus; (3)
most peristaltic contractions end with segmental, simultaneous contraction of the terminal
antrum and pyloric canal, closing the pylorus. Cineradiography showed that TAC and
the contraction that closed the pyloric canal started simultaneously, but the pyloric canal
usually closed earlier in the sequence than the rest of the "antrum"; it remained closed
throughout the continuation of the terminal antral contraction. Sometimes the pyloric
canal narrowed early in the cycle, without closing completely, so that intraluminal
contents moved through it into the duodenum while the antrum was contracting.
The maximum rhythmic frequency of TAC's corresponded to the rhythmic frequency of
gastric peristaltic contractions, namely 4 to 5 per minute in dogs and 3 per minute in man.
The frequency of Type I or Type II contractions corresponded to the frequency of the
basic electrical rhythm (BER).
With the exception of Golden (l937) and Edwards and Rowlands (l968), the authors
mentioned above did not base the concentric, segmental, simultaneous contraction of
what they called the terminal antrum (TAC) on any unique characteristic or specialization
of the musculature of the wall of this part of the stomach. Yet Forssell (l913), Cole
(l928) and Torgersen (l942) had stated previously that the forms of movement in this
region depended on the specialized muscular build which had been described by
themselves as well as by Cunningham (l906) (Chap. 3). It comes as some surprise to note
that in investigations of gastric motility in human subjects, the above anatomical findings
have been almost universally ignored. Only Golden (l937) stated that as far as motility
was concerned, the canalis egestorius of Forssell (l913) was the most important part of
the stomach; unfortunately he equated the term "antrum" with "canalis egestorius".
Forssell (1913) had been adamant that "antrum" had no basis in anatomical fact, whereas
canalis egestorius was a well defined anatomical entity.
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