Download GIT development Tube development Stomach Before intestinal

Tube development
• primitive gut
– in 4th week folding of embryo cause partial
incorporation of yolk sac into the embryo
GIT development
– foregut – buccopharyngeal membrane, lung bud,
ventral and dorsal mesentery
– midgut – from liver bud, communication with yolk
sac → vitelline duct (ductus
omphalomesentericus), only dorsal mesentery
– hindgut – cloacal membrane, ventral and dorsal
mesentery
Tube rotations
Pancreas development
Liver development
Stomach
• tilting of stomach
– around an axis located in the midpoint of
lesser curvature → forming of duodenal loop
Before intestinal rotation
• gut is too long, loop formation
• two loops
– duodenal loop – foregut and midgut
• rotation of stomach
• apex – liver bud, two pancreatid buds
– 90° CW around its longitudinal axis
– umbilical loop – midgut and hindgut
• left → anterior, right → dorsal
• apex – ductus omphalomesentericus
– also on distal part of esophagus
• fusing of duodenal loop with dorsal wall
Duodenal loop
• during stomach rotation touch the dorsal
wall and fuse with it
• → duodenum and pancreas are secondary
retroperitoneal organs
Umbilical loop
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axis – superior mesentery art.
is outside of body – physiological hernia
180° CCW around the axis outside
next 90° CCW during reposition
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Definitive position
• caecum grows
caudally and form
colon ascendens
Anomalies and malformations
• pylorostenosis – hypertrophy of sphincter
• omphalocoele – disorder of reposition
• covered only by amnion
• inborn umbilical hernia
• reposition OK, later herniated
• covered at least by peritoneum and amnion
• malrotation
– incomplete rotation
– reverse rotation
Hindgut
• cloaca division
Pancreas development
• 4th week
• caudal part of foregut
• 2 pancreatic buds
(11):
– dorsal (bigger)
– ventral
• stenosis and atresias
• anal imperforations × rectal atresias
• ductus vitellinus can persist as
– diverticulum Meckeli
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Pancreas development
– dorsal bud (7) grows to dorsal mesentery
– ventral bud (5) to ventral mesentery
– forms future uncinate process and part of caput
pancreatis
– migration of ventral pancreas cause fusing
of buds
Pancreas development
• insulin secretion starts in about 10th
week
• abnormalities of pancreas
– annular pancreas
• surrounds the duodenal wall, duodenal
stenosis
Liver development
– caudal part of foregut → liver bud (4th week)
– grows to ventral mesentery
Liver development
• liver bud division
– 1) cranial bud (larger)
• future liver
• bud grows through veins leading to heart to
septum transversum
– 2) caudal part
• origin of gallbladder
• forming of ductus cysticus
Liver development
– endodermal cells – hepatocytes
– septum transversum – hematopoetic cells,
Kupffer cells
– umbilical and vitelline veins – sinusoids
Liver development
– hematopoesis since 6th week
– last 2 month of intrauterine development
abates
– ventral mesogastrium:
• mesohepaticum → lig. falciforme hepatis
• omentum minus
– liver covered by peritoneum, only area nuda is
free
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