Question

define Re-Entry of the Midgut into the Abdomen

Answer 1

During the 10th week of de­velopment the herniated intestines re­turn to the abdomen. The exact cause of withdrawal of the intestine from the umbilical cord is not well understood. However, it has been proposed that decrease in the relative size of the liver and mesonephric kidneys and enlargement and expansion of the ab­dominal cavity play important role is retraction of the midgut into the abdo­men.
As the midgut loop returns to the abdomen, it rotates counterclockwise through an additional 180 degrees. The small intestine is the first to re-enter the abdominal cavity. In this process the jejunum leads and passes posterior to the superior mesenteric artery to oc­cupy the space in the left half of the abdomen cavity.
The returning coils of small in­testine also push the non-herniated de­scending colon (derived form the hind-gut) to the left side. The jejunum coils are followed by the coils of ileum which gradually settle more and more to the right. The caudal limb of the midgut loop (representing the cecum and proximal colon) is last to leave the um­bilical cord.
As it enters the abdominal cav­ity, its tendency to straighten carries this limb slantingly across to the right
side, thus completing a rotation that becomes retroperitoneal. The rest of totals 270 degrees. Consequently, the the midgut derivatives, ie, jejunum, i cecum comes to occupy a position just eum and transverse colon retain their inferior to the liver. At this stage the mesenteries. Here it may also be men-proximal colon passes obliquely from tioned that the mesentery of the devel-the cecum (which is located quite low oping colon (which is a hindgut deriva-on the right side in a subhepatic posi- tive) is absorbed and (like the ascend-tion) to the descending colon (located ing colon) it also becomes retroperito-in the left side of abdomen) and the as- neal.
cending and transverse colon 'can not The mesentery of jejunum and
be identified. ileum is at first attached at the midline
The ascending colon becomes of the posterior abdominal wall, but recognizable as the posterior abdomi- during the rotation of the midgut loop it nal wall elongates and the liver retreats twists around the origin of the superior in cranial direction due to a decrease in mesenteric artery. When the mesentery its size. At about the same time, the of the ascending colon is absorbed, the right colic (hepatic) flexure also ap- mesentery of the small intestine obtain pears and demarcates the ascending a new line of attachment extending from the transverse colon which from the duodenojejuqal junction passes in front of the duodenum to join obliquely down to the ileocecal junction the descending colon at the left colic in the right iliac fossa, (splenic) flexure. As described earlier, the mesen­ tery of the transverse mesocolon fuses Fixation of the Intestine with the posterior leaf of the greater
As various parts of the intestine omentum.  However,  it  maintains its
settle into their final  positions, their mobility because the greater omentum
mesenteries are pressed against the itself is a freely mobile structure, posterior abdominal wall. Some parts
of the intestine lose their mesenteries MeconJUITI
because their mesenteries fuse with At full term the large intestine is
the parietal  peritoneum and,  conse- fined with a dark green material called
quently, disappear. These parts of the meconium. This material is composed
intestine are then said to be retroperi- mainly of intestinal gland secretions,
toneal. bile, and swallowed amniotic fluid and
It has already been described vernix caseosa. The infant excretes
earlier that the mesentery of the duo- this material for a few days afterbirth, denum is abdsorbed and (except for the initial 2.5 cm) it becomes retroperi­toneal. The mesentery of the ascend­ing colon is also absorbed and it too
side, thus completing a rotation that becomes retroperitoneal. The rest of totals 270 degrees. Consequently, the the midgut derivatives, ie, jejunum, i cecum comes to occupy a position just eum and transverse colon retain their inferior to the liver. At this stage the mesenteries. Here it may also be men-proximal colon passes obliquely from tioned that the mesentery of the devel-the cecum (which is located quite low oping colon (which is a hindgut deriva-on the right side in a subhepatic posi- tive) is absorbed and (like the ascend-tion) to the descending colon (located ing colon) it also becomes retroperito-in the left side of abdomen) and the as- neal.
cending and transverse colon 'can not The mesentery of jejunum and
be identified. ileum is at first attached at the midline
The ascending colon becomes of the posterior abdominal wall, but recognizable as the posterior abdomi- during the rotation of the midgut loop it nal wall elongates and the liver retreats twists around the origin of the superior in cranial direction due to a decrease in mesenteric artery. When the mesentery its size. At about the same time, the of the ascending colon is absorbed, the right colic (hepatic) flexure also ap- mesentery of the small intestine obtain pears and demarcates the ascending a new line of attachment extending from the transverse colon which from the duodenojejuqal junction passes in front of the duodenum to join obliquely down to the ileocecal junction the descending colon at the left colic in the right iliac fossa, (splenic) flexure. As described earlier, the mesen­ tery of the transverse mesocolon fuses Fixation of the Intestine with the posterior leaf of the greater
As various parts of the intestine omentum.  However,  it  maintains its
settle into their final  positions, their mobility because the greater omentum
mesenteries are pressed against the itself is a freely mobile structure, posterior abdominal wall. Some parts
of the intestine lose their mesenteries MeconJUITI
because their mesenteries fuse with At full term the large intestine is
the parietal  peritoneum and,  conse- fined with a dark green material called
quently, disappear. These parts of the meconium. This material is composed
intestine are then said to be retroperi- mainly of intestinal gland secretions,
toneal. bile, and swallowed amniotic fluid and
It has already been described vernix caseosa. The infant excretes
earlier that the mesentery of the duo- this material for a few days afterbirth, denum is abdsorbed and (except for the initial 2.5 cm) it becomes retroperi­toneal. The mesentery of the ascend­ing colon is also absorbed and it too