Organ fixed _in situ_ when well filled.
]
The left extremity or fundus is large and rounded; it is the most dorsal
part of the organ, and lies under the dorsal ends of the eleventh and
twelfth ribs.
The pyloric extremity is small and is directed forward and somewhat
upward; it lies usually about an inch or two (ca. 3.5 to 5 cm.) below
the cardia, a little to the right of the median plane. It is related to
the portal fissure of the liver and to the pancreas.
[Illustration:
FIG. 333.—EVERTED STOMACH OF DOG FROM WHICH THE MUCOUS MEMBRANE IS
REMOVED.
_O_, Œsophagus; _D_, duodenum; _b_, circular fibers; _c′_, internal
oblique fibers; _c″_, cardiac loop; _c‴_, transition of internal to
external oblique fibers; _d_, fibers uniting branches of cardiac
loop; _p_, pyloric sphincter; _p′_, antral sphincter.
(Ellenberger-Baum, Anat. d. Haustiere.)
]
[Illustration:
FIG. 334.—DIAGRAM OF ZONES OF MUCOUS MEMBRANE OF STOMACH OF DOG.
]
The cardia is situated about two to three inches (ca. 5 to 7 cm.) from
the left extremity, and is oval; it lies a little to the left of the
median plane, below the tenth or eleventh thoracic vertebra.
When empty, or nearly so, the stomach is separated from the ventral
abdominal wall by the liver and small intestine, and the greater
curvature extends back to the eleventh or twelfth rib. In this state
there is not rarely a marked constriction between the right and left
portions.
The longitudinal muscular fibers are found on the curvatures and on the
pyloric part. The oblique fibers are arranged in two layers: the
external layer is a continuation of the longitudinal fibers of the
œsophagus onto the body and fundus. The circular layer covers the whole
stomach except the fundus, and forms a pyloric sphincter and an antral
sphincter. The internal oblique layer is arranged as in the horse, and
forms a similar loop-like, cardiac sphincter.
Three regions of the mucous membrane exist. Cardiac glands are found in
a very narrow pale zone around the cardiac opening, and also scattered
along the lesser curvature. The fundus gland region has a thick,
reddish-brown mucous membrane, which lines about two-thirds of the
organ. The pyloric mucous membrane is thinner and pale; in the dead
subject it is often stained by regurgitated bile.
[Illustration: