EX2 Embryology Flashcards
Which germ layer forms the epithelial lining and glands of the GI tract
endoderm
The endoderm that dorms the innermost lining of the gut tube is derived from where
the dorsal portion of the yolk sac
This duct connects the midgut and the yolk sac
vitelline duct
This membrane ruptures at week 4 and provides a continuity between the oral cavity and the foregut
oropharyngeal membrane; allows for swallowing of amniotic fluid
This membrane ruptures at week 7 and allow for urination and defication
cloacal membrane
Which germ layer forms the smooth muscles and the connective tissues of the GI tract
splanchnic mesoderm
This is the serous membrane lining the abdominal cavity and organs
peritoneum
This type of peritoneum lines the abdominal cavity
parietal peritoneum
This type of peritoneum lines the organs
visceral peritoneum
This is a double layer of peritoneum that suspends an organ from the body wall
mesentery
True or False
Mesentery can contain CT, blood vessels, lymphatics, and/or nerves
True
The peritoneum and mesentery are derived from what germ layer
sphanchnic mesoderm
At what level of the GI tract does the ventral mesentery exist
foregut; it is resorbed inferior to it
The ventral mesogastrium is divided into which two segments due to the outgrowth of which organ
falciform ligament
lesser omentum
liver
The lesser omentum (derived from what?) splits into what ligaments
LO is derived from ventral mesogastrium
hepatogastric ligament
hepatouodenal ligament
The dorsal mesogastrium forms what
greater omentum
The dorsal mesentery forms what four structures
dorsal mesogastrium
mesoduodenum
mesentery proper
mesocolon
The neural crest cells migrate into the walls of GI tract to form what
enteric nervous system (intrinsic nervous system)
This section of the GI tract is from the mouth to the first 1/2 of the duodenum
foregut
This section of the GI tract is from the second 1/2 of the duodenum to the first 2/3 of the transverse colon
midgut
This section of the GI tract is from the last 1/3 of the transverse colon to the anus
hindgut
The main blood supply to the GI tract is what
abdominal aorta (and its 3 branches)
The blood supply to the foregut is supplied via which artery
celiac trunk
The blood supply to the midgut is supplied via which artery
superior mesenteric artery
The blood supply to the hindgut is supplied via which artery
inferior mesenteric artery
The blood supply to the pharynx is supplied via which artery
pharyngeal arch
What six main structures are a part of the foregut
pharynx lower respiratory system esophagus stomach proximal 1/2 of duodenum associated organs (pancreas, liver, gall bladder, etc.)
The foregut/midgut divide is typical where
after the entrance of the pancreatic and bile ducts in the duodenum
The esophagus develops as the portion of the foregut immediately (cranial/caudal) to the pharynx
caudal
This appears on the ventral side of the foregut and will become the trachea, respiratory tree, and lungs, during what week
respiratory diverticulum
week 4
This appears from the lateral sides of the foregut, diving the foregut into the lower respiratory tract and esophagus
tracheoesophageal septum
This is the abnormal narrowing of a lumen/orifice (tubular organ or structure)
stenosis
This is a condition in which a body lumen or orifice is abnormally closed or absent
atresia
Causes of stenosis/atresia can include what four things
failure to reanalyze following a temporary epithelial plug
adequate blood supply fails to develop
accidents that compromise blood flow
mechanical obstruction
This is an abnormal passageway between two organs/vessels or between an organ and the external environment
fistula
Esophageal atresia and trachesophageal fistula can lead to what
risk of polyhydraminos (too much amniotic fluid)
During week 4, a portion of the foregut begins to dilate uniformly, this becomes what?
the stomach
As the stomach enlarges, its dorsal side expands faster than the other sides and it will be come the what? and the ventral side becomes this?
greater curvature
lesser curvature
The stomach will undergo a rotation that is which direction (this is caused by uneven distribution of weight)
90° clockwise rotation
During the stomachs 90° clockwise rotation, the ventral side ends up on what side and is supplied by what nerve
right side supplied via the left vagus
the dorsal side (left) is supplied via the right vagus
This is caused by the circular smooth muscles constricting the pyloric lumen preventing passage of the stomach contents to the SI
hypertrophic pyloric stenosis
As the stomach rotates, this is carried to the left
dorsal mesogastrium
As the dorsal mesogastrium is carried to the left by the stomach, it enlarges this into a sizable recess between the stomach and posterior abdominal wall
omental bursa (lesser sac of peritoneum)
This organ forms between two leaves of dorsal mesogastrium during week 5
spleen
This forms as a C-shaped loop distal to the stomach; supplied by both the celiac trunk and SMAl where the pancreatic and common bile ducts empty
duodenum
As the stomach rotates CW, it drags the distal duodenum and pancreas to where they become this; their dorsal mesenteries are lost
retroperitoneal (secondarily)
This is the failure of the lumen to recanalize in the duodenum by week 8; vomit will either contain or not contain bile depending on where the obstruction is located
duodenal stenosis and atresia
This emerges ventrally from endoderm of the distal foregut and grows superiorly toward the septum transvedsum (diaphragm) and gives rise to what three things
hepatic diverticulum
liver, gall bladder, and bile ducts
This organ emerges from distal foregut as two endodermal buds (ventral and dorsal)
pancreas
True or False
The ventral bud of the pancreas does not fuse with the dorsal bud
False; as the duodenum rotates, the ventral bud swings and fuses with the dorsal bud
The ventral bud go the pancreas becomes what two things
uncinate process
inferior portion of head of pancreas
The main pancreatic duct forms from which two ducts buds
distal portion of dorsal bud duct and ventral bud duct
The accessory pancreatic duct forms from what duct bud
proximal dorsal bud duct
This is caused when the ventral bud of the pancreas develops into two portions and they fail to fuse resulting in one wrapping around the duodenum then fusing
annular pancreas
The midgut is composed of these six main structures
distal 1/2 of duodenum jejunum ileum cecum and appendix ascending colon proximal 2/3 of transverse colon
The cranial limb of the midgut U-shaped loop forms which three structures
distal duodenum
jejunum
proximal ileum
The caudal limb of the midgut U-shaped loop forms which four structures
distal ileum
cecum and appendix
ascending colon
proximal 2/3 of transverse colon
This is when there is insufficient room in the abdominal cavity and it leads to temporary herniation of midgut loop into the proximal umbilical cord
physiological umbilical herniation
This is a persisting umbilical herniation; viscera covered by amnion and within proximal umbilical cord
congenital omphalocoele
This is when a hernia is through the body wall and does not involve the umbilical cord; exposure to amniotic fluid can damage the viscera
gastrochisis
During week 6 the midgut undergoes what type of rotation
90° counterclockwise
SMA is axis of rotation
During week 10 the midgut undergoes a second rotation of which is what?
180° counterclockwise which brings the intestines into normal position (270° total rotation)
True or False
The ascending and descending colon are intraperitoneal
False; they become secondarily retroperitoneal; their dorsal mesenteries are lost after fusion with parietal peritoneum of posterior abdominal wall
These five structures are considered intraperitoneal
proximal duodenum jejunum ileum transverse colon sigmoid colon
These five structures are considered retropeitoneal
distal duodenum pancreas ascending colon descending colon kidneys (form retroperitoneal)
This is the result if the caudal limb returns first from the midgut loop
left-sided colon
If there is an 180° clockwise (instead of counterclockwise) it results in a net 90° clockwise rotation which causes this to happen
the duodenum is now ventral to the TVC (doesn’t become retroperitoneal)
This is caused by abnormal rotation which may cause intestinal loop twist around mesenteric attachment site; can result in bowel obstruction/compromised blood flow leading to stenosis, necrosis, etc.
volvulus
The recanalization of the midgut loop occurs during what week
week 8
the epithelial cells occlude at week 6 and dissolve at week 8
This is a remnant of the vitelline duct persisting as a finger-like out-pouching of the ileum about 40-60cm from the ileocecal junction; may contain tissue/gastric mucosa that secretes acid; causing ulcers/bleeding
Meckel’s (ileal) diverticulum
What are the three variations of a persistent vitelline duct
vitelline fistula
vitelline cyst
vitelline ligament
The hindgut is composed of these five structures
distal 1/3 transverse coon descening colon sigmoid colon rectum superior portion of anal canal
These two structures are derived from the posterior portion of the cloaca after it is partitioned by the urorectal septum
rectum
superior portion of anal canal
This grows inferiorly toward the cloacal membrane dividing it into urogenital and anal membranes
urorectal septum
The urorectal septum partitions the cloaca into what two things
urogenital sinus (ventrally) anorectal cana (dorsally)
What two arteries supply the anal canal
superior rectal artery supplies the portion of the anal canal from the hindgut
inferior rectal artery supplies the portion distal to that
This form if the urorectal septum fails to completely separate the hindgut from the urogenital sinus or if the cloaca is too small
hindgut fistula (anal canal not connected to anal pit)
This disease is a result of when neural crest cells fail to migrate to form the enteric nervous system; causing constriction of the aganglionic portion and bowel distending proximal to the constriction
Hirschspring’s disease (aganglionic megacolon)
