Development of GI system
Terms in this set (60)
Yolk sac endoderm gives rise to
gut epithelium and glands.
Connective tissue and muscle of the gut is derived from
artery that supplies foregut
exceptions to the celiac artery supplying to foregut
pharynx, respiratory tract and the intra-thoracic esophagus
artery that supplies midgut
superior mesenteric artery
artery that supplies hindgut
inferior mesenteric artery
Parasympathetic innervation of gut
Vagus nerve innervates foregut and midgut, while pelvic splanchnic nerves (S2-4) supply the hindgut.
The adult derivatives of the foregut include:
Pharynx and its derivatives
Lower respiratory system
Esophagus and Stomach
Duodenum -superior half, distal to the opening of common bile duct
Liver, biliary system and pancreas
SKIPPED ESOPHAGUS CAUSE REVIEW
development of the stomach
During week 4, the caudal foregut develops a dilation that gives rise to the stomach
the greater and lesser curvatures of the stomach
the dorsal side grows faster than the ventral side creating these two curvatures.
the stomach rotates 90 degrees. The original left side becomes the ventral surface; original right side becomes dorsal surface. The mesenteries create a greater sac and a lesser sac after rotation.
Left vagus nerve supplies the ventral wall; right vagus nerve supplies dorsal wall.
also called stomach mesogastrium. Has a dorsal one and a ventral one.
Dorsal Mesogastrium becomes
the greater omentum, as well as the gastrosplenic and splenorenal ligaments in the adult.
the ventral mesogastrium becomes
the lesser omentum. It connects the lesser curvature of the stomach to the liver and duodenum. It also makes the falciform ligament which connects the liver to the abdominal wall.
spleen is derived from
mesenchymal cells between the layers of the dorsal mesogastrium.
foramen through which the lesser sac (omental bursa) communicates with the rest of the peritoneal cavity.
Hypertrophic pyloric stenosis
narrowing of the pylorus obstructing the passage of food. Newborns will projectile vomit and have a small knot at the right costal margin.
What antibiotic when given to infants causes increased instances of hypertrophic pyloric stenosis?
The duodenum is derived from
the caudal foregut and cranial midgut.
What divides the foregut and the midgut?
the attachment of the bile duct
this is the term for an organ which was peritoneal in the embryo (was held in place by the peritoneum or ligaments) and due to folding changed position becomes retroperitoneal.
How stomach folding effects the duodenum
Rotation of the stomach rotates the duodenal loop to the right. Both the pancreas and the duodenum are pushed into a secondarily retroperitoneal position.
duodenal epithelium proliferation
occludes the lumen, and then it is recannalized by weeks 8-9.
Clinical condition occurs when the lumen is narrowed as a result of failed recanalization.
Results when the lumen is occluded as a result of failed recanalization. Often associated with POLYHYDRAMNIOS due to low intestinal reabsorption of amniotic fluid.
Seen on pre-natal u/s. The first bubble corresponds to the stomach and the second to the post-pyloric and pre-stenotic dilated duodenal loop. Sign of duodenal atresia or stenosis.
Because the duodenum is derived from two sources it has two blood supplies, name them:
the part of the duodenum from the foregut is supplied by the celiac, the part from the midgut is supplied by the superior mesenteric artery.
dorsal and ventral pancreatic buds
grow out of the foregut endoderm between the dorsal and ventral mesentery. Duodenal rotation carries the ventral bud to meet the dorsal and they fuse making the pancreas.
Ventral pancreatic bud forms
part of the pancreatic head, uncinate process and most of main pancreatic duct; dorsal bud forms the rest of pancreas.
occurs when the ventral pancreatic bud splits to fuse with the dorsal bud both ventrally and dorsally, forming a ring of pancreatic tissue around the duodenum. Clinical signs include duodenal obstruction shortly after birth.
made of foregut endoderm. Becomes the liver and gallbladder.
The hepatic diverticulum divides into:
Cranial portion, and caudal portion
forms the liver. This portion grows rapidly during weeks 5-10, filling most of the abdomen. Hematopoiesis begins in week 6; bile production begins in week 12.
gallbladder & cystic duct. The gall bladder's endodermal lining proliferates & occludes the lumen; later, recanalization occurs.
the bile duct is formed by
Common stalk connecting the hepatic and cystic ducts to the duodenum.
Extrahepatic biliary atresia
usually presents as obliteration of the bile ducts, resulting in jaundice soon after birth.
The midgut forms:
o Most of small intestine (except proximal duodenum via foregut) o Cecum and vermiform appendix
o Ascending colon
o Right half of transverse colon.
yolk stalk (vitellineduct)
the midgut has an open communication with the yolk sac through this. It gets smaller and smaller till its gone.
has a caudal limb and a cranial limb. Loop around the superior mesenteric artery.
physiological umbilical herniation
the midgut loop herniates out into the extra embryonic ceolom because of lack of space. Goes back in by week 10.
cranial limb of the midgut loop develops into
the jejunum and upper ileum.
caudal limb of the midgut develops into
The lower ileum, ascending colon and proximal 1⁄2 of transverse colon.
rotates 90 degrees, moving the cranial limb (small intestine) to the right and the caudal limb (large intestine) to the left.
reduction of the midgut hernia
what they call it when the midgut returns to the abdomen. It returns cranial limb, then caudal, then cecum, and it folds intricately placing the intestines in the basic position they will be in the adult. It affects the mesenteries of the intestine, and pushes the duodenum and pancreas secondarily retroparitoneal.
Malrotations of the midgut
present with intestinal obstruction shortly after birth. They predispose the infant to volvulus, where there is twisting of intestines around a short mesentery, often interfering with intestinal blood supply.
is the persistence of midgut herniation in the umbilical cord. The herniated intestine fails to return to the abdominal cavity. The herniated gut is enclosed by the epithelium of the umbilical cord.
occur when the midgut hernia reduces normally, but herniates again through an imperfectly closed umbilicus either pre or postnatally. In this case, the herniated bowel is covered by subcutaneous tissue and skin.
results from a defect in the ventral abdominal wall. Abdominal viscera extrude through a split in the abdominal wall without umbilical cord involvement. This condition results from incomplete embryonic folding.
Ileal (Meckel's) diverticulum
involves the persistence of the proximal yolk stalk and is one of the most common anomalies of the GI tract. May be asymptomatic, or It may become inflamed and present like appendicitis. Sometimes contains portions of gastric mucosa in its walls, producing ulceration and bleeding.
the cranial end of the hindgut develops into
the distal 1⁄2 of transverse colon, descending and sigmoid colon.
The terminal end of the hind gut is
an endoderm lined pouch called the cloaca, which develops into the rectum and superior anal canal.
the cloaca divides into
an anterior portion (urinary) and a posterior portion (digestive).
the cloacal membrane lies at the base of
the anal pit known also as the proctodeum.
the urorectal septum
is a mass of mesodermal cells that grows down to divide the cloaca. This divides the cloaca into the urorectal membrane, and the anal membrane.
the anal canal comes from two sources
the hindgut growing down makes the endoderm portion, the distal portion is made of ectoderm. the junction between these is the pectinate line. These two sections have different blood supply, different innervation which makes it relevant.
Congenital megacolon (Hirschsprung's disease)
is a neurological dysfunction that affects the colon. An abnormality in autonomic ganglia causes failure of peristalsis in the aganglionic segment. Intestinal contents accumulate proximal to this point, enlarging the colon.
is a condition in which the rectum ends too far superior, either blindly or with a fistula to the bladder
types of fistula
between rectum and vagina, between rectum and urinary tract
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