9:00:00 AM
Movements of
the Stomach
Q. What are the movements of the stomach?
A. The cardiac
portion of the stomach is not subject to regular movements during digestion. It
remains quiescent, a fact which permits of the orderly stratification
of the foodstuffs, the last portions eaten
entering the center of the globular mass which is
formed in the cul-de-sac. Peptic digestion goes on at the surface of the mass, while the salivary
digestion proceeds in the center and may continue for two or three hours from the beginning of the meal. As fast as the food is liquefied at the center of the alimentary
mass it goes through the pylorus where it is
mixed with the pyloric secretion containing pepsin,
which begins its work in the stomach and continues in
the intestine.
The movements of the stomach are not confined to the pylorus. Infrequent rhythmical movements
occur in the pre-pyloric portion, but the pyloric portion contracts regularly
every ten seconds during digestion, making
2500 to 3000 contractions during the digestion of a meal. The pyloric
movements begin as soon as the
liquefied portions of the food reach this
part of the stomach. If peptone is
introduced into the stomach, the pylorus
movements begin immediately. Introduction of meat
into the stomach induces no movement. Fear and anger arrest instantly the movements of the stomach when in full activity.
When the stomach is empty,
rhythmical movements occur every two hours,
lasting twenty to thirty minutes. These
movements start in the stomach and extend to
the entire intestine and are accompanied by a slight secretion of
gastric juice, bile, pancreatic and intestinal juices. These movements are absent
during digestion and disappear during long fasts. The stomach is controlled
both by the sympathetic and pneumogastric nerves. In the sympathetic nerves
the inhibitory fibers predominate ; in the pneumogastric nerves the excito-motor
nerves predominate, although the inhibitory nerves are present. In fasting the
excito-motor influence of the pneumogastric diminishes rapidly and disappears
wholly at the end of three days, so that the stomach is wholly under the
influence of the inhibitory functions of the sympathetic and pneumogastric
nerves. This probably accounts for the fact that at the end of the first three
days fasting persons experience much less inconvenience than before this time,
also for the intestinal inactivity which is present when fasting.
There are various measures by which the gastric
movements may be excited to increased activity. Water at a temperature of 100°
to 102° F. stimulates the action of the stomach. This is probably the reason
that water at this temperature encourages vomiting.
Water at a higher or lower temperature lessens gastric activity. Water
at a temperature of 41° F. arrests all movements of the stomach and prevents
the action of other stimulants. This is clearly a good reason for prohibiting
the use of iced drinks and frozen foods of all sorts. Faradic currents cause
contraction of the gastric walls. More efficient contractions
are secured by a slowly alternating sinusoidal
current. Gastric contractions are also produced by the galvanic current but
these contractions occur only at the opening and closing of the circuit.
The most active excitant of the movements of the
stomach are the products of gastric digestion. Peptones,
hydrochloric acid in solution, 1 to 5 parts in 1000, excite no movements
of the fundus of the stomach while exciting the movements of the pylorus.
Sometimes anti-peristaltic movements are set up by extreme acidity, which explains
the eructation of acids.
According to Battelli, strychnia
is entirely without effect upon the motility
of the stomach. In view of this fact, it is
surprising that this drug should be so extensively used as a gastric stimulant,
since it exercises a most unfavorable influence upon
secretion while rendering no service.
An ice bag placed
at the epigastrium causes gastric
contractions. Lavage is also an excellent means of
stimulating gastric contractions, in cases
of gastric inactivity. Insufficiency of the cardiac
orifice gives rise to regurgitation of food-stuffs and merycism. Pyloric insufficiency allows a reflux of bile into the
stomach. Vomiting of bile only takes place when the reflux is intermittent.
Continuous insufficiency of the pylorus gives rise to diarrhea very soon after
eating.