The Digestive System
and duodenum (the ﬁrst part of the small intestine), and parts
of the large intestine, are called
behind). By contrast, digestive organs (like the stomach) that
keep their mesentery and remain in the peritoneal cavity are
is inﬂammation of the peritoneum. It can arise from
a piercing abdominal wound, a perforating ulcer that leaks
stomach juices into the peritoneal cavity, or poor sterile tech-
nique during abdominal surgery. However, most commonly it
results from a burst appendix that sprays bacteria-containing
the digestive viscera; hold organs in place; and store fat. In most
places the mesentery is
and attaches to the posterior ab-
dominal wall, but there are
mesenteries too, such as the
one that extends from the liver to the anterior abdominal wall
(Figure 23.5a). Some digestive organ mesenteries have speciﬁc
names (such as the
), or are called “ligaments” (even
though these peritoneal folds are nothing like the ﬁbrous liga-
ments that connect bones).
Not all alimentary canal organs are suspended by a mesentery.
For example, during development, some regions of the small in-
testine adhere to the dorsal abdominal wall (Figure 23.5b). In so
doing, they lose their mesentery and come to lie posterior to the
peritoneum. Tese organs, which include most of the pancreas
(sight, smell, taste,
thought of food)
Central nervous system
Extrinsic visceral (autonomic)
wall (site of short
Lumen of the
Neural reﬂex pathways initiated by stimuli inside or outside the
(a) Two schematic cross sections of abdominal cavity illustrate
the peritoneums and mesenteries.
(b) Some organs lose their mesentery and move,
becoming retroperitoneal, during development.
Alimentary canal organ in
a retroperitoneal position
The peritoneum and the peritoneal cavity.
Note that the peritoneal cavity is
much smaller than depicted here.