Digestive System Embryology Flashcards
establishes the 3 germ layers of the embryo during 3rd week of development; begins with formation of the primitive streak on the surface of the epiblast
gastrulation
all 3 germ layers contribute to the formation of the ____
GI tract
_____ of the neuroectoderm become neurons of the ______
neural crest cells; enteric nervous system
the mesoderm germ layer contributes to the formation of ____, _____, and _____
connective tissue; muscular components; peritoneal components
the endoderm contributes to ____ of GI tract and ____ of glands
epithelium; parenchyma
____ covers the ventral surface of the embryo and forms the roof of the yolk sac
endoderm
as a result of body folding during the 4th week, the endoderm is incorporated into the embryo to form the _____
primitive gut tube
the specific cells of a gland or organ held together by connective tissue called the stroma
parenchyma
the endoderm gives rise to specific cells (parenchyma) of glands, such as ____ and the ____ and ____ cells of the ______
hepatocytes; exocrine; endocrine; pancreas
the stroma of the glands of the GI tract is derived from _____
visceral mesoderm
during cephalocaudal or cranial caudal folding in the ____ direction progresses, the opening of the gut tube into the yolk sac narrows until it forms a small connection called the ____
sagittal; vitelline (yolk sac) duct
the vitelline duct is between the ____ and the ____
midgut; yolk sac
the vitelline (yolk sac) duct is incorporated into the ____, becomes very narrow, and degenerates with the yolk sac around 2nd-3rd months of development
umbilical cord
the foregut extends from the ____ to _____
oropharyngeal membrane; liver outgrowth
the oropharyngeal membrane separates the ____ from the ____
stomodeum (primitive oral cavity, derived from ectoderm); pharynx (a part of the foregut, derived from endoderm)
in the 4th week, the oropharyngeal membrane ruptures, establishing open connection between ____ and ____
oral cavity; primitive gut
the midgut begins _____ and extends to _____
caudal to liver bud; proximal 2/3 of transverse colon
hindgut is from _____ to _____
distal 1/3 of transverse colon; cloacal membrane
the cloacal membrane separates the ____ (derived from endoderm) from the ____, which is formed by an invaginating pit lined by ectoderm
upper part of the anal canal (derived from endoderm);
lower part of anal canal (from ectoderm)
cloacal membrane breaks down in 7th week to create the opening for the ____
anus
double layer of peritoneum that encloses an organ and connects it to the body wall
mesentery
thin serous membrane that lines walls of abdominal cavity
peritoneum
organs which are completely enclosed in mesentery and connected to wall via mesentery
intraperitoneal
organ that lies against posterior body wall and is covered with peritoneum on anterior surface only
retroperitoneal
the dorsal mesentery is formed via ____ meeting and fusing in the midline
visceral mesoderm layers
the _____, ____, and the _____ are suspended from the posterior body wall via dorsal mesentery
caudal part of the foregut; midgut; major part of the hindgut
the dorsal mesentery extends from the _____ to the _____
lower end of the esophagus; cloacal region of the hindgut
divisions of dorsal mesentery
- dorsal mesogastrium (greater omentum): dorsal mesentery in region of the stomach
- mesoduodenum: dorsal mesentery in region of duodenum
- dorsal mesocolon: dorsal mesentery in region of the colon
- mesentery proper: dorsal mesentery of jejunal and ileal loops
ventral mesentery is derived from the ____
septum transversum
septum transversum is mesodermal tissue that gives rise to the ____ and _____
central tendon of diaphragm; connective tissue in the liver
ventral mesentery exists only in region of ____, ____, and _____
terminal esophagus; stomach; upper part of duodenum
liver grows in the ____ of the septum transversum, dividing ventral mesentery into:
mesenchyme; lesser omentum and falciform ligament
lesser omentum extends from _____, ____ and _____ to the _____
lower portion of esophagus; stomach; upper portion of the duodenum; liver
the falciform ligament extends from ___ to ____
liver; ventral body wall
free inferior margin of the falciform ligament; contains obliterated umbilical vein
round ligament of the liver (ligamentum teres hepatis)
free margin of lesser omentum connecting duodenum and liver; contains portal triad
hepatoduodenal ligament
portal triad components
bile duct, portal vein, and hepatic artery
opening that connects omental bursa (lesser sac) with the rest of the peritoneal cavity (greater sac)
epiploic foramen of winslow
each gut region is supplied by one of the 3 major arteries off the _____
abdominal aorta
foregut is supplied by ____, midgut is supplied by ____, and hindgut is supplied by ____
celiac (trunk) artery; superior mesenteric artery; inferior mesenteric artery
foregut derivatives:
- esophagus
- trachea and lung buds
- stomach
- duodenum (proximal to entrance of bile duct)
- liver
- biliary apparatus (hepatic ducts, gallbladder, bile duct)
- pancreas
appears at ventral wall of foregut at about the 4th week; is initially in open communication with foregut
respiratory diverticulum (lung bud)
foregut divides into _____ (ventral) and _____ (dorsal)
respiratory primordium; esophagus
upper 2/3 of esophagus contains:
striated muscle and vagus nerve
lower 1/3 of esophagus contains:
smooth muscle and splanchnic plexus
when the respiratory diverticulum expands caudally, two longitudinal ridges called ______ separate it from the foregut
tracheoesophageal ridges
the tracheoesophageal ridges fuse to form the _____, thereby dividing the foregut into a dorsal portion (_____) and a ventral portion (_____)
tracheoesophageal septum; esophagus; trachea and lung buds
the stomach appears as ____ of _____ (4th week)
fusiform dilation; foregut
stomach rotates along ____ and _____ axis
longitudinal; anteroposterior
stomach rotates _____ around its longitudinal axis
90 degrees clockwise
the original left side will now face _____
anteriorly
the left vagus nerve will innervate the ____ of the stomach
anterior wall
the original right side will now face _____
posteriorly
the right vagus nerve will innervate the _____
posterior wall of the stomach
concurrent with stomach rotation, the original posterior wall grows faster than the original anterior portion, leading to ____ and ____
greater and lesser curvatures
the caudal part of the stomach, or the ____, moves upward and to the right
pylorus
the cephalic part of the stomach or the _____, moves slightly downward and to the left
cardia
the stomach is attached to the dorsal body wall via _____
dorsal mesogastrium
rotation pulls dorsal mesogastrium to the left, creating space behind the stomach called _____
omental bursa (lesser peritoneal sac)
appears as mesodermal proliferation between the two leaves of the dorsal mesogastrium (5th week)
spleen primordium
connected to body wall in the region of the left kidney
lienorenal ligament
connected to stomach
gastrolienal ligament
spleen remains ____
intraperitoneal
as a result of stomach rotation, the _____ bulges down and grows inferiorly
dorsal mesogastrium
the dorsal mesogastrium forms a double-layered sac that extends over the ____ and _____; the layers fuse to form a single sheet that hangs from the greater curvature of the stomach called the _____
transverse colon; small intestine loops; greater omentum
the duodenum is formed from the ____ and _____
terminal part of foregut; cephalic part of midgut
as stomach rotates, duodenum becomes ____ and rotates to the ____
C-shaped loop; right
rotation, together with rapid growth of head of ____, swings duodenum from midline to ___ side of abdomen
pancreas; right
____ and ____ press against dorsal body wall and become fixed in ____ position
duodenum; head of pancreas; retroperitoneal
a small portion of the duodenum, the ____, near pylorus of stomach, retains mesentery and is ____
duodenal cap; intraperitoneal
_____ disappears completely except in region of pylorus of stomach
dorsal mesoduodenum
during 2nd month, ___ of duodenum is ____ due to cell proliferation within its wall (called ____)
lumen; obliterated; “solid stage”
lumen is ____ (becomes patent) shortly after
recanalized
the duodenum is derived from ___ and ____ i.e. its blood supply comes from ____ and _____
foregut; midgut; celiac (trunk) artery; superior mesenteric artery
in the middle of the 3rd week, _____ appears at the ____ as an outgrowth of the endodermal epithelium
liver primordium; distal end of the foregut
this outgrowth, known as the _____ (______), consists of rapidly proliferating cells that penetrate the _____
liver bud (hepatic diverticulum); septum transversum
white hepatic cells invade the septum transversum, the connection between the liver bud and foregut (duodenum) narrows, forming the _____
(common) bile duct
a small ventral outgrowth is formed by the bile duct; this outgrowth gives rise to the ____ and ____
gallbladder; cystic duct
the pancreas is formed by 2 buds:
a dorsal pancreatic bud and a ventral pancreatic bud
the pancreatic buds originate from the ____ lining of the _____
endodermal; duodenum
the ____ is within the _____ and the ____ is close to the ____
dorsal bud; dorsal mesentery; ventral bud; bile duct
when the duodenum rotates to the right, the _____ also rotates to the right, moving _____
ventral pancreatic bud; dorsally
the ventral bud comes to lie immediately ____ and ____ the dorsal bud
below; behind
the ventral bud forms:
uncinate process and the inferior part of the head of the pancreas
dorsal bud forms:
all other parts of the pancreas
formed by distal part of dorsal pancreatic duct and entire ventral pancreatic duct
main pancreatic duct (of Wirsung)
main pancreatic duct, together with ____, enters duodenum at _____
bile duct; major (duodenal) papilla
formed by proximal part of dorsal pancreatic duct
accessory pancreatic duct (of Santorini)
entrance of accessory pancreatic duct
minor (duodenal) papilla
In the 3rd month of fetal life, ______ develop from parenchyma & scatter throughout the pancreas
pancreatic islets (of Langerhans)
_____ begins at about the 5th month
insulin secretion
______ & _____ cells also develop from parenchymal cells
glucagon-secreting; somatostatin-secreting
2 major roles of the pancreas
- enzymatic production and secretion (exocrine)
2. hormonal production and secretion (endocrine)
pancreatic islets (of Langerhans) are regions containing ____/_____
endocrine cells; hormone-producing cells (i.e. alpha cells, beta cells, etc.)
blood supply to midgut
superior mesenteric a.
at ____, midgut communicates with yolk sac via _____
5 weeks; vitelline duct (yolk stalk)
in the adult, the midgut begins just distal to the entrance of the _____ into ____
bile duct; duodenum
in the adult, the midgut terminates at _____ with ____
junction of proximal 2/3 of transverse colon; distal 1/3
rapid elongation of the gut and its mesentery results in formation of the _____
primary intestinal loop
loop remains in contact with yolk sac via _____
vitelline duct (yolk stalk)
cephalic limb becomes:
- distal part of duodenum
- jejunum
- part of the ileum
caudal limb becomes
- lower portion of ileum
- cecum
- appendix
- ascending colon
- proximal 2/3 of transverse colon
Development of primary intestinal loop characterized by ______, particularly of the _____
rapid elongation; cephalic limb
Due to rapid growth & expansion of ____, abdominal cavity temporarily becomes _____ to contain all the _____
liver; too small; intestinal loops
in the ___ week, the intestinal loops enter the extraembryonic cavity in the umbilical cord, known as _____
6th; physiological umbilical herniation
As primary intestinal loop lengthens, it concurrently rotates around an axis formed by the ______
superior mesenteric artery
midgut rotation is a ____
270 degree counterclockwise rotation (when viewed from the front)
first 90 degrees of this rotation occurs during _____
umbilical herniation (about 6th week)
remaining 180 degrees of this rotation occurs during _____ into _____
return of intestinal loops; abdominal cavity (10th week)
Retraction of herniated loops occurs during the 10th week; it is not precisely known what factors are responsible for return of intestinal loops back to the abdominal cavity; however, it is thought that _____, _____, and _____ play important roles
regression of the mesonephric kidney; reduced growth of the liver; expansion of the abdominal cavity
In 2%-4% of individuals, small portion of vitelline duct persists as an outpocketing of the ileum known as ______
Meckel diverticulum (ileal diverticulum)
meckel diverticulum is usually ____, but may contain pancreatic tissue or gastric mucosa , which can cause ____, ____, or ____
ulceration; bleeding; perforation
Both ends of vitelline duct may develop into fibrous cords, with the middle portion forming a large cyst known as a ______
vitelline cyst (enterocystoma)
Intestinal loops may twist around the fibrous strands of the vitelline cyst and become _____, causing _____
obstructed; strangulation
Vitelline duct remain patent over its entire length, leading to direct communication between the umbilicus and the intestinal tract; fecal discharge may be found at the umbilicus
vitelline fistula
When _____ & _____ colons obtain their final positions, their mesenteries press against ____ of posterior abdominal wall
ascending; descending; peritoneum
Via fusion of these layers, the ascending & descending colons are permanently anchored in a _____ position
retroperitoneal (secondarily retroperitoneal)
the ____, lower end of ____, and ____ retain their free mesenteries and are _____
appendix; cecum; sigmoid colon; intraperitoneal
_____ fuses with posterior wall of greater omentum, but maintains its mobility (intraperitoneal)
transverse mesocolon
mesentery of jejunoileal loops
mesentery proper
line of attachment of mesentery proper extends from area where duodenum becomes ____, to the _____
intaperitoneal; ileocecal junction
transverse mesocolon’s line of attachment extends from ____ of ____ to _____ of _____
hepatic flexure; ascending colon; splenic flexure; descending colon
hindgut gives rise to:
- distal 1/3 of the transverse colon
- sigmoid colon
- rectum
- upper part of anal canal
endoderm of the hindgut forms ____ of the ____ and ____
internal lining; bladder; urethra
hindgut supplied by ____
inferior mesenteric artery
endoderm-lined cavity covered at its ventral boundary by surface ectoderm
cloaca
the boundary between the endoderm and ectoderm forms the ____
cloacal membrane
wedge of mesoderm that separates the region between the allantois and hindgut
urorectal septum
the tip of the urorectal septum grows inferiorly toward the ____
cloacal membrane
the tip of the urorectal septum divides the cloacal membrane into ____ and ____ membranes; partitions the cloaca into ____ (ventrally) and _____ (dorsally)
urogenital; anal; urogenital sinus; anorectal canal
at the end of week ____, the cloacal membrane ruptures, creating anal opening for the hindgut and ventral opening for the _____
7; urogenital sinus
superior 2/3 of anal canal derived from ____ of ____
endoderm; hindgut
inferior 1/3 of anal canal derived from invaginating ____ around ____
ectoderm; proctodeum
ectoderm in region of the ____ proliferates and invaginates to create ____
proctodeum; anal pit
the cloacal membrane (now called the ____) degenerates and establishes continuity between upper and lower parts of the _____
anal membrane; anal canal
junction between ____ and ____ regions of the anal canal is delineated by _____
endodermal; ectodermal; pectinate line
epithelium changes from ____ to _____
columnar; stratified squamous epithelium
also known as the “anal pit”; it is an ectodermally-lined pit in the terminal portion of hindgut that invaginates to form the lower 1/3 of the anal canal
proctodeum
proctodeum initially separated from the rest of the anal canal by the _____, which breaks down to permit continuity between the two parts of the canal
anal membrane
