GI-Embryology Flashcards
What part of the GI is derived from the foregut?
the pharynx to the duodenum
What part of the GI is derived from the midgut?
duodenum to the proximal 2/3 of the transverse colon
What part of the GI is derived from the hindgut?
distal 1/3 of transverse colon to the anal canal above the pectinate line
Failure of the rostral fold closure in the anterior abdominal wall during development can lead to what?
sternal defects
Failure of the lateral fold closure in the anterior abdominal wall during development can lead to what?
omphalocele (below), gastrochisis
NOTE: Gastrochises is extrusion of abdominal contents NOT covered by peritoneum, while omphalocele is herniation of GI contents into the umbilical, which IS sealed by peritoneum
Failure of the caudal fold closure in the anterior abdominal wall during development can lead to what?
bladder extrophy
Extrophy of the bladder is also associated with what?
epispadiasis
What is Duodenal atresia?
also known as duodenojejunal atresia, this is the congenital absence or complete closure of a portion of the lumen of the duodenum.
Duodenal atresia is most commonly associated with what?
Down syndrome- trisomy 21
How would duodenal atresia be identified on a CXR?
Radiography shows a distended stomach and distended duodenum, which are separated by the pyloric valve, a finding described as the double-bubble sign.
How does duodenal atresia affect pregnancy?
During pregnancy, duodenal atresia is associated with polyhydramnios, due to the inability of the fetus to swallow the amniotic fluid and absorb it in their digestive tract.
How does duodenal atresia present at birth?
After birth, duodenal atresia may cause abdominal distension, especially of the upper abdomen. Bilious vomiting commonly occurs within the first day of life. The vomiting is described as “bilious,” because it contains bile acid.
Familial multiple intestinal atresia, an inherited AR disorder, is caused by what?
mutation in the gene TTC7A on short arm of chromosome 2
This is usally fatal
What is the most common cause of non-doudenal atresia?
vascular accident in utero that leads to decreased intestinal perfusion and ischemia of the respective segment of bowel. This leads to narrowing, or in the most severe cases, complete obliteration of the intestinal lumen.
What is the characteristic appearance of a non-duodenal atresia caused by occlusion of the superior mesenteric artery, or another major intestinal artery?
large segments of bowel can be entirely underdeveloped. Classically, the affected area of bowel assumes a spiral configuration and is described to have an “apple peel” like appearance; this is accompanied by lack of a dorsal mesentery. Ileal atresia can also result as a complication of meconium ileus.
Describe development of the midgut
Around the 6th week gestation, the midgut herniates through the umbilical ring and returns to the abdominal cavity around 10 weeks , when it rotatoes around the SMA
Pathology of this process includes possible formation of omphalocele, intestinal atresia, volvulus (below)
Esophageal atresia with distal tracheoesophageal fistula (TEF) is the most common type (85%)
What is the ‘pylorus’?
The pylorus, or pyloric part, connects the stomach to the duodenum. The pylorus is considered as having two parts, the pyloric antrum (opening to the body of the stomach) and the pyloric canal (opening to the duodenum). The pyloric canal ends as the pyloric orifice, which marks the junction between the stomach and the duodenum. The orifice is surrounded by a sphincter, a band of muscle, called the pyloric sphincter.
How would congenital pyloric stenosis be identified?
via a palpable ‘olive shaped’ mass (seen on CXR) in the epigastric region and nonbilious projectile vomit at around 2-6 weeks old
What kinds of babies is congenital pyloric stenosis more common in?
fristborn males
What does congenital pyloric stenosis result in?
hypokalemic, hypochlormeic metabolic alkaosis 2ndary to vomiting of gastric acid
Where does the pancreas derive from?
the foregut
How does the pancreas develop?
the ventral pancreatic buds cpntribute to the uncinate process and main pancreatic duct, and the dorsal pancreatic vue alone becomes the body, tail, isthmus, and accessory pancreatic duct
Both the ventral and dorsal buds contribute to the pancreatic head
What is an ‘annular’ pancreas?
this occurs when the ventral pancreatic bud abnormally encirles the 2nd part of the duodenum forming a ring of pancreatic tissue that may cause duodenal narrowing
What is a pancreas divisum?
this occurs when the ventral and dorsal parts of the pancreas fail to fuse at 8 weeks
