GI Development Flashcards
Label the GI system
Label the Embryo (mid 3rd week)
Label the embryo in early 4th week
Label the image (embryo in early 4th week with the amniotic sac removed)
Label the embryo at 4 weeks
- Entrance to yolk sac is squished into ________
Entrance to yolk sac is squished into vitelline duct
Label the diagram
What does the blue region become?
Blue region becomes the respiratory system
_______ coats the endodermal tube
splanchnic mesoderm coats the endodermal tube
label the layers of the primitive gut tube
The pink region is _____ and becomes _______
The yellow region is _____ and becomes _______
The pink region is splanchnic mesoderm and becomes everything except for epithelium (Smooth muscle, connective tissue)
The yellow region is endoderm and becomes epithelium of intestines (mucosa)
Label the mature gut
Which signalling molecules are present in the gut during development?
Shh → (+)Bmp4 | (-)Smap
Bmp4 → + Shh
Smap → smooth muscle genes
Label the image:
Numbers 2-6 represent aortic arches
label the image of blood supply to gut
What are the three arterial branches to the abdominal gut?
- Celiac artery
- Superior mesenteric artery
- inferior mesenteric arter
The _______, arising from the edge of teh neural plate gives rise to the entire peripheral nervous system, including the enteric nervous system
The neural crest cells gives rise to the entire peripheral nervous system, including the enteric nervous system
The neural crest cells, arising from the ________ gives rise to the ________
The neural crest cells, arising from the edge of teh neural plate gives rise to the entire peripheral nervous system, including the enteric nervous system
The enteric nervous system originates at the ________ and migrates/differentiates along the primitive gut tube
The enteric nervous system originates at the vagal neural crest and migrates/differentiates along the primitive gut tube
The foregut includes (5)
- Pharynx
- Esophagus
- Stomach
- Superior half of duodenum (to Ampulla of Vater)
- Celiac Trunk (abdominal foregut)
The formation of _____ separates developing respiratory system from developing esophagus
The formation of tracheoesophageal septum separates developing respiratory system from developing esophagus
Label the image (embryonic stomach)
Why does the stomach develop curvatures?
Because the left side grows more (patterning cues) → more proliferation
The gut is anchored to the dorsal body wall by a double-layer of _______ derived from the _________
The gut is anchored to the dorsal body wall by a double-layer of mesothelium (mesentery) derived from the splanchnic mesoderm
Functions of the mesenteries?
Anchoring and organization
Conduit for vasculature/lymphatics/nerves
Difference between the Ventral and Dorsal mesenteries?
- Ventral mesentery
- _____ only
- Chunk of _______ associated with heart tissue (________) that gave rise to the _______ (over which the diaphragm formed)
- Dorsal Mesentery
- _________
- Ventral mesentery
- Foregut only
- Chunk of splanchnic mesoderm associated with heart tissue (cardiogenic mesoderm) that gave rise to the septum transversum (over which the diaphragm formed)
- Dorsal Mesentery
- Runs length of gut (Abdomen to rectum)
How is the Omental bursa/Lesser sac formed?
- An invagination of coelomic epithelium in the mesoderm on the right side gives rise to a recess that expands to the left and posterior/dorsal to the stomach
As the omental bursa grows, the ________ also grows
As the omental bursa grows, the mesoderm associated with the greater curvature also grows = greater omentum
What is the omental bursa/lesser sac?
The omental bursa or lesser sac is a hollow space that is formed by the greater and lesser omentum and its adjacent organs
the lesser sac/omental bursa communicates with the greater sac via the ________
the lesser sac/omental bursa communicates with the greater sac via the epiploic foramen of winslow,
The expanding mesoderm that grows with the bursa creates the _______
The expanding mesoderm that grows with the bursa creates the greater omentum (apron)
Function of greater omentum?
“Policeman of Abdomen” → walls off infection, forms adhesions and locks spread
Conduit for immune cells
The Midgut includes: (8)
Vasculature?
- Inferior half of duodenum
- Jejunum
- Ileum
- Cecum
- Appendix
- Ascending colon
- Right ⅔rds of transverse colon
Superior mesenteric artery
The _______ occurs at the base of the umbilical cord where body folding converges
The midgut herniation occurs at the base of the umbilical cord where body folding converges
At the base of the umbilical cord where body folding converges there is a ______ coated by ______
At the base of the umbilical cord where body folding converges there is a connecting stalk coated by membrane of amnion
Label the image:
What development happens during midgut herniation?
The small intestine increases 20x in length
Large intestine increases 8x
As it grows, bending/folding/coiling => loops
Label the current model of midgut movement (during herniation)
How is the midgut returned to the abdomen?
Label the image:
At approximately 10-11 weeks the abdomen enlarges and the intestines return to the abdominal cavity. The midgut then rotates an additional 180 degrees counter-clockwise, fixing to the posterior retroperitoneum
What happens with the obliteration of the vitelline duct?
Yolk sac is released into the amniotic cavity
Which organs are secondarily retroperitoneal viscera (stuck on posterior body wall)?
- Duodenum
- Pancreas
- Ascending colon
- Descending colon
Which organs are retroperitoneal viscera (outside the peritoneum)?
- Thoracic esophagus
- Rectum
How do the duodenum, pancreas, ascending colon and descending colon (which all start as intraperitoneal) move to a secondarily retroperitoneal viscera position?
- Started intraperitoneal then squished to posterior layer of somatic mesoderm → gives rise to parietal peritoneum → grows over → stuck to wall → anchor points
Which organs are intraperitoneal viscera?
- Abdominal esophagus
- Liver
- Gallbladder and bile duct
- Stomach
- Transverse colon
- jejunum and ileum
- Cecum
- Appendix
- Sigmoid colon
How does the anterior body wall change with return of herniation (from 6 weeks to 9 weeks)?
- The abdominal gap (diastasis) is closed because the rest of the body grows making the gap appear smaller
What are the organs of the hindgut and what artery supplies them?
- Left ⅓ of transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Superior portion of anal canal
Supplied by Inferior Mesenteric Artery
What divides the cloaca at about 28-32 days?
The Urorectal septum
Divides into the anterior urogenital sinus and posterior rectum
What is on the anterior side of the urorectal sinus? The Posterior?
- Anterior → Urogenital sinus and allantois (finger of endoderm protruding into the umbilical cord)
- Posterior → Rectum
By 7 weeks, the _____ has grown into the cloacal membrane and completely divided the anterior and posterior portions of the cloaca.
At that point, what happens?
By 7 weeks, the urorectal septum has grown into the cloacal membrane and completely divided the anterior and posterior portions of the cloaca.
At that point, what happens?
- The membrane ruptures opening the lower GI and urinary tracts to the amniotic cavity (septum breaks down the cloacal membrane)
What happens at the anal canal after the cloacal membrane bursts (following urorectal growth)?
- The ectoderm around the opening to the anus proliferates, creating a temporary plug (center cells)
- The central cells of the plug undergo apoptosis creating a new opening
- Therefore, the lower part of the anal canal is derived from ectoderm not endoderm
The lower part of the anal canal is derived from _______, why?
The lower part of the anal canal is derived from ectoderm (not endoderm), why?f
because the ectoderm around the opening to the anus proliferates, creating a temporary plug, the central cells of this plug undergo apoptosis creating a new opening
What divides the ectoderm (inferior) and endoderm-derived (superior) portions of the anal canal?
The ectoderm and endoderm-derived portions of the anal canal are divided by the pectinate line (tooth-like appearance)
What is the importance of the pectinate line in terms of hemorrhoids classification?
- Internal hemorrhoids
- Above pectinate line (endoderm-derived)
- Not painful
- External hemorrhoids
- Below pectinate line (ectoderm derived)
- Painful
Label the chart
Label the chart
All digestive glands (______, ______, _______) all start as ______
All digestive glands (liver, pancreas, gall bladder) all start as evaginations of the primitive gut tube
Liver starts as an ______ that grows ______ just below the ______
Liver starts as an evagination that grows ventrally (into ventral mesentery4) just below the stomach
The liver and gall bladder start as _______ surrounded by ______
The liver and gall bladder start as pockets of endoderm surrounded by splanchnic mesoderm
What makes the function regions of the liver and gall bladder?
Endoderm
What are the three phases of liver development?
- Liver diverticulum
- Liver bud initiation
- Liver bud hepatic hematopoiesis
What gives rise to blood vessels during liver development?
Endothelial cells
What are the liver progenitor cells?
Hepatoblasts
The Hepatic progenitors, _______, are derived from ______ and make the ________
The Hepatic progenitors, hepatoblasts, are derived from endoderm and make the functional cells (hepatocytes and cholangiocytes)
Splanchnic mesoderm makes ______ (liver)
Splanchnic mesoderm makes stroma/smooth muscle
How does the pancreas develop?
- Starts as _____ which are pockets off primitive gut tube on ventral and dorsal side
- Grow off the _____ into ______ and off _____ side into the _____
- Pushed together during development onto ______ side of gut tube
How does the pancreas develop?
- Starts as pancreatic buds which are pockets off primitive gut tube on ventral and dorsal side
- Grow off the ventral side into ventral mesentery and off dorsal side into the dorsal mesentery
- Pushed together during development onto left side of gut tube
Where is the head of the pancreas located?
Head of pancreas tucked into the bend of the duodenum (C-shape pushed against posterior wall)
Connection for pancreas join at ______
Connection for pancreas join at bile ducts
Pancreas develops with ______ inside and _____ outside
Pancreas develops with endoderm inside and splanchnic mesoderm outside
Endoderm → functional cells and ducts
Splanchnic mesoderm → CT/ smooth muscle/stroma
