Module 5 - Development of the Digestive System, Heart, & Great Vessels Flashcards
When does the GI tract first appear?
during the process of gastrulation from the endoderm of the trilaminar embryo
How does the ectoderm contribute to the GI tract?
enteric nervous system from neural crest cells
How does the mesoderm contribute to the GI tract?
CT, smooth muscle, blood vessels, mesentery of the GI tract
How does the endoderm contribute to the GI tract?
epithelial lining of the GI tract, liver, gallbladder, pancreas
How is the gut tube formed?
when the embryo folds ventrally, endoderm sheet forms a closed tube surrounded by mesoderm
What are the 3 regions in the gut tube?
foregut, midgut, hindgut
What portion of the GI tract is the foregut and what blood vessels supplies it?
oral cavity to the duodenum is supplied by the celiac artery
What portion of the GI tract is the midgut and what blood vessels supplies it?
mid-duodenum to the first 2/3 of the transverse colon is supplied by the superior mesenteric artery
What portion of the GI tract is the hindgut and what blood vessels supplies it?
last 1/3 of the transverse colon to the anus is supplied by the inferior mesenteric artery
What is a mesentery?
double layer membrane formed from splanchnic mesoderm that suspends the gut tube and its derivatives from the dorsal and ventral body wall
What composes the dorsal mesentary?
greater omentum, mesoduodenum, mesentery proper, mesocolon
What composes the ventral mesentary?
falciform, triangular, and coronary ligament of the liver, lesser omentum, peritoneal coverings of the liver
What are the steps to esophagus development?
elongation - responsible for the repositioning of the stomach in the abdomen
occlusion - proliferation of the endoderm (week 5)
recanalization - reforms a hollow tube (week 9)
What 4 regions is the stomach made up of?
cardia, fundus, body, pylorus
How does the stomach appear in week 4 of development?
gastric dilation in the foregut
How does the stomach rotate during development?
longitudinal rotation - rotates 90*
anteroposterior rotation - rotates so that the pylorus moves cranially and the cardia moves caudally
Why are the greater and lesser curvatures of the stomach formed?
because differential growth, one border of the dilation elongates quicker than the other
What happens to the dorsal mesentery during rotation of the stomach?
pulls the greater omentum to the left and creates the gastrosplenic and splenorenal ligaments
What do the liver and gallbladder arise from?
the hepatic diverticulum
What are the steps to liver and gallbladder development?
formation of the hepatic diverticulum - grows from the distal end of the foregut and penetrates the diaphragm
division of the hepatic diverticulum - divides into the parenchyma (functional liver) and the gallbladder and cystic duct
hepatic duct formation - connection between diverticulum and foregut grows forming the hepatic duct
overgrowth of the hepatic duct - gives rise to the gallbladder and the cystic duct
liver cords differentiate - form the lining of the biliary ducts
liver stroma forms - CT capsule of the liver is derived from the diaphragm
How does the pancreas develop?
from 2 outgrowths of the gut tube endoderm
What are the 2 outgrowths that form the pancreas?
dorsal and ventral pancreatic bud
Where does the dorsal pancreatic bud develop from?
the duodenum
Where does the ventral pancreatic bud develop from?
bile buct
What happens to the ventral and dorsal pancreatic buds?
- ventral bud migrates dorsally towards the dorsal bus
- ventral bud fuses with the dorsal bud
- ducts also fuse; main pancreatic duct and bile duct fuse
After fusion, what does the ventral pancreatic bud become?
the uncinate process
After fusion, what does the dorsal pancreatic bud become?
main body of the pancreas
What is the midgut comprised of?
distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, 2/3 of the transverse colon
What are the steps to midgut development?
elongation - forms the primary intestinal loop (week 5)
herniation - primary loop continues to loop and grow and herniates become the abdomen is too small
rotation - intestinal loop rotates 90*
retraction - intestinal loop returns to the abdominal cavity and will complete another 180* rotation
How does the top of the intestinal loop and the yolk sac communicate?
via the vitelline duct
What artery does the intestinal loop complete its first 90* rotation around?
the superior mesenteric artery
What is the hindgut comprised of?
the distal 1/3 of the transverse colon, the descending colon, rectum, superior anal canal
What 4 major structures development the hindgut?
cloaca - shared end of the hindgut and urogenital tract
urorectal septum - migrates to the cloacal membrane and separates the the hindgut and urinary system
perineal body - cloacal membrane divides into the urogenital and anal membranes leaving the perineal body between them
anal pit - ectoderm invaginates the anal membrane to establish continuity between the anal canal and rectum
What is the proximal 2/3 of the anal canal derived from?
endoderm
What is the distal 1/3 of the anal canal derived from?
ectoderm
What are the 2 ganglion neuron networks in the enteric nervous system?
myenteric and submucosal plexus
Where is the myenteric plexus situated?
between the inner circular and outer longitudinal muscle layers of the intestines
Where is the submucosal plexus situated?
in the submucosa layer of the intestines
What is the enteric nervous system a derivative of?
the autonomic nervous system
Where do enteric nervous system neurons come from?
neural crest cells
What is the role of the enteric nervous system?
functions with the smooth muscle and intestinal villi to control absorption and secretion in the GI tract
When does heart tube formation begin?
middle of week 3 with the appearance of cardiac progenitor cells
What are progenitor cells derived from?
intraembryonic mesoderm and the cranial/3 of the primitive streak
How do the progenitor cells migrate to form the heart tube?
- migrate in a craniolateral direction within the lateral plate mesoderm and form localized groups that sit to the right and left of the primitive streak (heart fields)
- form a U shaped tube around the developing notochord
How does embryonic folding change the heart tube?
longitudinally - positions the tube in the thorax
laterally - allow for endocardial tubes to fuse
What is the bulbus cordis divided into?
truncus arteriosus, conus cordis, primitive ventricle, primitive atrium
What is the truncus arteriosus?
outflow tracts of the aorta and pulmonary arteries
What is the conus cordis?
outflow tracts of the right and left ventricles
What is the primitive ventricle?
walls of the ventricles
What is the primitive atrium?
divide into the left and right atria
What is the sinus venosus connected to?
the venous system
What happens to the heart as it continues growing?
restricted by the diaphragm and the pericardium so it must bend to continue growing
What happens to the heart structures throughout development?
primitive atria move posteriorly and the bulbus cordis come to lie between the primitive right and left atria
What separates the right and left atria in the adult heart?
interatrial septum
What separates the right and left ventricles in the adult heart?
interventricular septum
What are the 3 stages of development of the interatrial septum?
septum primum - proliferating cells from the atria roof flow caudally towards the endocardial cushion
ostium primum - opening between the endocardial cushion and septum primum
ostium secundum - another opening in the septum primum after fusion with the endocardial cushion
septum secundum - another proliferating septum from the atria roof grows caudally to cover the ostium secundum
What is the foramen ovale?
oval shaped window that allows blood to pass between the atria covered by a thin flap of the septum primum
How does the foramen ovale allow for the shunting of blood?
allows the oxygenated blood coming from the placenta pass through to the left ventricle to bypass pulmonary circulation
What happens to the foramen ovale at birth?
septum primum and secundum fuse and close off the foramen
What will the aortic sac develop into?
the future aorta
What is the ventral aorta?
the right and left branches of the aortic sac
What are the aortic arches?
6 arteries that branch off each ventral aorta
What do the aortic arches wrap around and follow the structure of?
the pharyngeal arches
What is the dorsal aorta?
connect to the aortic arches and connect back to the aortic sac
What do the aortic arches supply blood to?
their associated pharyngeal arch
What happens to aortic arch 1, 2, and 5?
they disappear
What happens to aortic arch 3?
become the internal carotid arteries and common carotid arteries (dorsal aorta), external carotid arteries (ventral aorta)
What happens to aortic arch 4?
right subclavian (right ventral) and aortic arch (left ventral)
What happens to aortic arch 6?
right and left pulmonary arteries and ductus arteriosus
What does the sinus venosus receive blood from?
vitelline, umbilical, and cardinal veins
What do the vitelline veins drain?
the yolk sac
What do the umbilical veins do?
carry oxygenated blood to the embryo
What do the cardinal veins drain?
body of the embryo
What having to the embryonic veins?
veins on the left tend to regress and veins of the right enlarge and give rise to the great veins
