Alimentary and Paraalimentary Tract Embryology Flashcards
The process of embryonic folding of the gut tube will capture a part of the ______ in the formation of the lumen.
yolk sac
The continuity between the lumen of the forming GI tract and the midgut is maintained via the _____ duct which becomes a part of the _____.
vitelline duct –> incorporated into the umbilicus
The gut tube is surround by derivatives of which embryonic layer?
endoderm
The gut tube is suspended in the central body cavity by ______.
mesentery
The coming together of the ______ folds at the ventral midline leads to the separation of the body cavity from the outside world.
lateral
The midgut opening narrows to form the vitelline duct by day ____.
26
How many invaginations of the sac roof are required to form the gut tube?
3: cranila, lateral, caudal invaginations
The _______ membrane marks the future position of the mouth and seals the cranial end of the gut tube.
oro/buccopharyngeal membrane
Another name for the oral cavity.
stomodeum
The _______ membrane marks the future position of the rectum and seals the caudal end of the gut tube.
cloacal membrane
The _______ coelom forms with the completion of embryonic folding and becomes the ______ cavity.
intraembryonic coelom –> peritoneal cavity
At week 5 the endodermal gut tube is hollow/solid/recanalizing?
hollow
At week 6 the endodermal gut tube is hollow/solid/recanalizing?
solid and occluded by endodermal proliferate
At week 7/8 the endodermal gut tube is hollow/solid/recanalizing?
recanalizing
At week 9 the endodermal gut tube is hollow/solid/recanalizing?
definitively hollow gut
3 complications of the gut recanalization process
atresia: blockage of tube
stenosus: narrowing of tube
duplication: blind branch of gut tube exists in parallel to main branch
The thoracic foregut lies above the _______ and consists of what structures?
septum transversum // contains pharynx and respiratory diverticulum
Immediately inferior to the septum transversum lies the _____ and consists of what structures?
abdominal foregut: stomach, superior duodenum, liver, pancreas, gallbladder
The midgut extends from the ______ to the _____.
inferior duodenum to partway through the transverse colon
The hindgut extends from the ______ to the ______.
transverse colon to the rectum
T/F foregut/midgut/hindgut are divided up based on embryological significance.
F –> based on regional bloodsupply/anatomy
The area of the gut supplied by aortic branches is called the:
thoracic foregut
The area of the gut supplied by celiac branches is called the:
abdominal foregut
The area of the gut supplied by SMA is called the:
midgut
The area of the gut supplied by IMA is called the:
hindgut
Foregut/Midgut/Hindgut (F/M/H)? pharynx
F
Foregut/Midgut/Hindgut (F/M/H)? Inferior duodenum
M
Foregut/Midgut/Hindgut (F/M/H)? Jejunum
M
Foregut/Midgut/Hindgut (F/M/H)? Thoracic Esophagus
F
Foregut/Midgut/Hindgut (F/M/H)? Transverse Colon Left 1/3
H
Foregut/Midgut/Hindgut (F/M/H)? Descending colon
H
Foregut/Midgut/Hindgut (F/M/H)? Abdominal esophagus
F
Foregut/Midgut/Hindgut (F/M/H)? Ileum
M
Foregut/Midgut/Hindgut (F/M/H)? Stomach
F
Foregut/Midgut/Hindgut (F/M/H)? Sigmoid Colon
H
Foregut/Midgut/Hindgut (F/M/H)? Rectum
H
Foregut/Midgut/Hindgut (F/M/H)? Transverse Colon Right 2/3s
M
Foregut/Midgut/Hindgut (F/M/H)? Ascending Colon
M
Foregut/Midgut/Hindgut (F/M/H)? Appendix
M
Foregut/Midgut/Hindgut (F/M/H)? Cecum
M
Foregut/Midgut/Hindgut (F/M/H)? Superior dudoenum
F
Foregut/Midgut/Hindgut (F/M/H)? Lungs
F
Foregut/Midgut/Hindgut (F/M/H)? liver/hepatic duct/gallbladder/cystic duct/bile duct/dorsal and ventral pancreatic buds
F
Foregut/Midgut/Hindgut (F/M/H)? Pharyngeal pouch derivatives
F
Foregut/Midgut/Hindgut (F/M/H)? Urogenital sinus
H
The formation of the lung bud begins on day ___
25
Complete blockage or narrowing o the esophagus due to failure of recanalization
esophageal atresia and stenosis
Caudal displacement of the septum between the trachea and esophagugs results in incomplete separation of the respiratory and esophageal tubes, named what?
Tracheoesophageal Fistula
A failure of the esophagus to elongate displaces part of the stomach into the thoracic cavity (short esophagus) leading to a condition called ____.
congenital hiatal hernia
Why does the stomach gain curvature and therefore have a greater/dorsal and lesser/ventral curvature?
the dorsal wall/mesentery grows faster than the ventral wlal
Why does the greater curvature of the stomach end up on the left?
a differential thinning of the dorsal mesentery leads to a 90 degree rotation of the stomach
How is the caudal end of the gut tube suspended?
by the dorsal mesentery whereas the cranial end has both a dorsal and a ventral mesentery
T/F Rotation of the stomach is genetically controlled?
T –> a differential change in cell shape/packing leads to left right asymmetry due to stomach rotation
Duodenal atresia and stenosis
complete blockage or narrowing of the duodenal lumen due to a failure of recanalization and a proximal dilation of the duodenum
How does duodenal atresia present on ultrasound?
double bubble –> appearance of stomach and proximal duodenum are dilated and fluid filled
The ______ expands to form the greater omentum.
dorsal mesentery
The ______ of the stomach is the lesser omentum.
ventral mesentery
The _______ of the peritoneal cavity is located dorsal to the stomach.
lesser sac
The two peritoneal compartments are connected by the _______
epiploic foramen
By what day is the peritoneum divided into two cavities?
36-40 days
On day 22 the _____ forms on the ventral surface of the superior duodenum.
hepatic plate
Proliferation of the hepatic plate forms the ____ which grows into the _________.
hepatic diverticulum –> ventral mesentery
The ventral mesentery connects the liver to the stomach via the lesser omentum and to the ventral body wall via the _____
falciform ligament
The hepatic diverticulum gives rise to what 3 structures?
hepatic cords, hepatic duct, and bile canaliculi
On day 26, the ________ forms on the ventral duodenum caudal to the hepatic diverticulum.
cystic diverticulum
The cystic diverticulum leads to the formation of what strucutres?
gallbladder and cystic duct
Cells at the junction of what two structures proliferate to form the bile duct?
junction of the hepatic and cystic ducts
Splitting of the cystic diverticulum is called _____ and is symptomatic/asymptomatic.
gallbladder duplication –> asymptomatic
Obstruction of the bile duct occurs in 1:10,000 births due to a failure to canalize leading to a condition called what?
extrahepatic biliary atresia
The bile ducts initially form as a hollow/solid tube and then undergo canalization/recanalization.
The bile ducts form as solid cords and are canalized to form hollow tubes (vs. the gut tube which forms as a hollow cord and then becomes solid and then undergoes recanalization)
On day 26, the ________ forms on the dorsal duodenum and grows into the dorsal mesentery. The _______ forms on the ventral duodenum, caudal to the __________ and grows into the ventral mesentery.
dorsal pancreatic bud // ventral pancreatic bud is caudal to the hepatic and cystic diverticuli
During weeks 5-6, the _______ pancreatic bud migrates around the duodenum to fuse with the other bud.
ventral pancreatic bud
The ______ degenerates upon fusion of the two pancreatic buds and the ____ becomes the main pancreatic connection to the duodenum.
The dorsal duct degenerates // the ventral duct becomes the main connection
Anular pancreas
two attached ventral buds rotate in opposite directions to fuse with the dorsal bud, causing duodenal stenosis or atresia.
The process by which the pancreas and the duodenum fuse with the dorsal body wall is called _____
fixation
Structures initially suspended from mesenteries that become attached to the body wall (duodenum, pancreas, colon)
secondarily retroperitoneal (e.g. duodenum, pancreas, colon)
Structures suspended by mesenteries within the peritoneal cavity (stomach, gallbladder, transverse colon)
intraperitoneal (e.g. stomach, gallbladder, transverse colon)
Structures attached to the body wall outside the peritoneal cavity
retroperitoneal (e.g. thoracic esophagus, rectum)
During week 5-6, the ____lengthens more rapidly than the abdominal cavity causing the midgut to fold into the primary intestinal loop.
ileum
The cranial half of the intestinal loop forms what structures?
the ileum
The caudal half of the intestinal loop forms what structures?
ascending and transverse colon.
The ______ end of the intestinal loop is attached to the umbilicus.
Ventral
By week 6, the elongation of the midgut forces the intestinal loop to herniate into the ______.
umbilicus
As the primary intestinal loop herniates into the umbilicus, it rotates 90 degrees so the cranial half moves to the right/left and the caudal half moves to the right/left.
cranial moves right, caudal moves left
During week 10, the intestinal loop retracts into the abdominal cavity and undergoes what movement?
an additional 180 degree rotation
The intestinal loop rotates a total of ____ degrees.
270
By week 11 the _____ is fixed to the dorsal body wall while the ileum and transverse colon remain suspended by mesenteries.
ascending colon
Herniation of the intestines into the umbilical cord due to a failure of the midgut to return to the abdomen at week 10.
congenital omphalocele
A failure of the umbilicus to close completely results in intestinal herniation following appropriate return to the abdomen.
umbilical hernia
Extrusion of midgut structures through the ventral body wall due to incomplete lateral folding during week 4.
Gastroschisis.
A remnant of the yolk stalk persists as an outpouching of the ileum-can contain gastric or pancreatic tissue and cause appendicitis-like symptoms.
ilela/meckel’s diverticulum
Nonrotation
a failure of rotation leading to opposite organ siding
A failure of fixation can lead to ________
midgut volvulus –> can occlude gut canal or cause ischemia
The hindgut forms an expansion called the cloaca that is sealed by the ______.
cloacal membrane
During weeks 4-6, the cloaca is divided into the rectum and urogenital sinus by the ______.
urorectal septum
The urorectal septum fuses with the _____ to form a ____ and a ____ separated by the perineum
fuses with the cloacal membrane to form a urogenital membrane and an anal membrane
Proliferation of the anal membrane forms the _____
anal pit
In week 8 the anal pit invaginates to form the _____
anorectal canal
What is the embryologic origin of the anorectal canal?
top 2/3 = endoderm, bottom 1/3 = ectoderm
The visible junction between the ectoderm and the endoderm of the anorectal canal is called _____
the pectinate line
Dilation of a region of the colon due to a peristalsis defect-caused by a failure of neural crest migration (weeks 5-7) and enteric ganglion formation.
congenital megacolon/hirschsprung’s –> distal aganglionic segment is narrowed, ganglionic proximal segment is distended
Failure of anal perforation during week 8.
membranous atresia
