Glossary of 3-Development of GI Tract
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- What helps in forming the primitive gut tube?
- longitudinal and lateral folding
- What are the three parts of the developing GI? What do members of each part share?
- foregut, midgut, hindgut
similar vascular supply, innervation, and lymph vessels, similar referred pain
- What is the consequence of lateral folding?
- endodermal ling of the upper part of the Yolk Sac is incorporated into the embryo and forms the lining of the primitive gut
- The cephalic part of the gut is called what? caudal?
- What attaches the primitive gut to the body wall? Is it fixed of suspended?
- dorsal mesentery
- As folding of the gut occurs what happens to the splanchnic mesoderm? Why is this important?
- right and left sides of splanchnic mesoderm fold toward each other
these lateral folds merge in the midline and form dorsal and ventral mesentery
- What differs between dorsal and ventral mesentery?
- the ventral mesentery only forms to the foregut segment
the dorsal mesentery goes to all parts
- Why are mesenteries referred to as being 'two-layered' thick of 'bilayered'?
- b/c they have origins from both the right and left splanchnopleure
- How are nevers and vessels able to reach the developing GI?
- What are the derivatives of the primitive dorsal mesentery? Where does each go to?
- dorsal mesogastnum-to stomach
the mesentery-small intestine (jejunum & ileum)
transverse mesocolon-transverse colon
sigmoid mesocoln-sigmoid colon
- Anatomically and clinically, what are mesenteries known as?
- bilayered visceral peritoneum or visceral peritoneal folds
- What is the layer of splanchnopleure enclosing an organ called?
- visceral peritoneal covering
- What is the mesoderm lining the body wall called? What is the wall called?
- parietal peritoneum
- What are the EARLY derivatives of the foregut?
- stomach, liver and gall bladder
- What does the liver form between?
- the two 'layers' of the ventral mesentery
- What artery supplies the foregut? midgut? hingut?
M-Superior mesenteric A
H-Inferior mesenteric A
- The stomach is initally attached to the ventral wall by the ventral mesentery (as well as to the dorsal wall by dorsal mesentery). What is this ventral mesentery later called?
- lesser omentum
- Which side of the stomach is faster growing? What does this create?
- dorsal surface, creates Greater Curvature
- Why is a long mesenteric fold hanging freely from the stomach in some adults?
- the original dorsal mesogastrium grows much more than its adjacent dorsal mesentery
- Why does the Lesser Curvature form? What side is this located on?
- the ventral surface does not match the growth pace of the dorsal surface
- Which way does the stomach rotate? What does this do to the original dorsal and ventral sides?
- rotates 90 to the right
dorsal swept to left, ventral moves toward right
- What creates a bulge near the junction of the stomach and esophagus? What is this called?
- differential growth in the cranial end of the stomach tube
called the fundus
- What is the notch that is between the fundus and the esophagus?
- cardiac incisure
- What is the name of the region of the stomach located distally?
- pyloric region
- What does the ventral mesentery become partitioned by?
- What is the proximal part of the ventral mesentery between? What is this called?
- between stomach and liver
called lesser omentum
- Which way does the lesser omentum move when the stomach rotates?
- What are the two parts of the lesser omentum?
- hepatogastric ligament
- Which ligament of the lesser omentum is more inferior? Which is smaller?
- hepatoduodenal ligament for both
- What is the distal part of the ventral mesentery between? What is it called?
- between liver and ventral body wall
- What is the narrowing of the pyloric of the stomach called?
- hypertrophic pyloric stenosis
- What is the cause of hypertrophic pyloric stenosis?
- thickening of the circular muscle in the wall of the stomach
- What creates the 'blind pouch' posterior to the stomach? What is this called?
- rotation of the stomach dragging along its attached mesenteries
- What does the omental bursa come off of?
- peritoneal cavity
- What is another name for the omental bursa?
- lesser peritoneal sac
- What binds the lesser peritoneal sac?
- lesser omentum, stomach, dorsal mesogastrium and posterior body wall
- What is the entry point to the lesser peritoneal sac called? Where is this opening located?
- omental foramen
caudal to the inferior edge of the lesser omentum
- What is the clinical importance of the lesser peritoneal sac?
- it's an important entry point for the spread of pathology into the bursa
- What is the spleen derived from?
- mesoderm (not endoderm)
- The spleen begins as mesenchymal condensations within what?
- dorsal mesogastrium
- What is the result of the 'clumps' that make the spleen?
- a notched border on the spleen is seen in adults
- What does the spleen deveop between?
- R&L layers of the dorsal mesentery
- Which side of the body is the spleen on? What causes it to move in this direction?
due to repositiong of the mesentery w/ the rotation of the stomach
- What does the spleen subdivide? What are the divisions named?
splenorenal (lienorenal) ligament and gastrosplenic (gastrolienal) ligament
- What forms the left boundary of the lesser peritoneal sac?
- splenorenal and gastrosplenic ligaments
- What forms the hepatic diverticulum? What part of the gut does this bud from?
- hepatic plate of tissue from duodenal/gastric area
- What keeps the hepatic diverticulum connected to the foregut?
- hepatic duct (stalk)
- What do the liver cords eventrually become?
- What do the spaces in the mesodermal core between the liver cords become?
- hepatic sinusoids
- What bud does the hepatic duct give rise to? What will this go on to form?
- cystic diverticulum
will develop gall bladder
- What will the proximal hepatic duct be called?
- common bile duct
- Where does the common bile duct empty its contents?
- What is the biliary duct system composed of?
- cystic duct attached to hepatic duct, the proximal part of hepatic duct is called the common bile duct
- What causes the liver to be in the RUQ?
- the liver grows rapidly, neighboring organs grow slower and stomach rotates
- How much weight does the liver account for at birth?
- What is the ventral mesentery partitioned by?
- What is the proximal part of the ventral mesentery called? distal?
- lesser omentum
- Which region of the gut is the ventral mesentery found?
- What is the remnant of the umbilical vein called?
- ligamentum teres hepatis
- Where does the umbilical vein run?
- along the inferior free margin of the ventral mesentery
- What makes up the portal triad?
- hepatic artery & (portal) vein, and bile duct
- What ist he reflection of peritoneum from the liver's surface tot he inferior surface of the diaphragm called?
- coronary ligament
- Does the bare area of the liver have a peritoneal or non-peritoneal surface?
- What is the duodenum derived from?
- distal end of foregut and proximal end of midgut
- What is the vascular supply of the duodenum?
- celiac trunk and SMA
- What are the four parts of the duodenum?
- 1-duodenal bulb (cap)
- At what part of the duodenum is the entry point for the duct system from the liver
- descending segment
- What is reduction in the size of the duodenum w/ abnormal narrowing of the gut segment? At what part of the duodenum does this normally occur?
- duodenal stenosis
3 or 4
- What is canalization? How does this relate to duodenal stenosis?
- normally, duodenal lumen fills w/ cells, but lumen is re-opened by the process of canalization, in duodenal stenosis there is incomplete recanalization
- What is duodenal atresia?
- abnormal degeneration of the duodenum
- Which type of duodenal anomality has bile in the vomit? Duodenal atresia or dudenal stenosis?
- both do
- What is the ventral bud of the pancreas associated with?
- hepatic duct
- What will the ventral bud of the pancreas become? dorsal bud?
- uncinate process (fishhook shaped)
neck, body and tail
- What does the duct of the ventral bud become?
- main pancreatic duct
- The main pancreatic duct and bile duct combine to form what?
- hepatopancreatic duct
- The hepatopancreatic duct expands to form what?
- ampulla of Vater
- What part of the duodenum does the ampulla of vater enter?
- 2nd part
- What is the major duodenal pailla?
- the raised mucosal tissue present on the duodenum where the hepatopancreatic duct enters
- What is the old attachment of the duct from the original dorsal bud of the pancreas called?
- minor papilla
- What does the tail of the pancreas grow between?
- dorsal mesogastrium , toward the spleen
eventually within the splenorenal ligament
- Which type of pancreatic cells produce digestive enzymes? What do these cells differentiate from?
- exocrine cells, from pancreatic bud endoderm
- Which type of pancreatic cells are in the islets of Langerhans? What are 2 things they have been suggested to come from?
- endocrine cells, from neural crest cells or gut endoderm
- What is Annular Pancreas? What can this cause?
- bilobed ventral pancreatic bud
the two ends migrate around the duodenum causing strangulation (duodenal atresia or stenosis)
- What part of the small intestine is midgut derived?
- distal half of duodenum, all of jejunum and illeum
- What part of the large intestine is midgut derived?
- cecum, appendix, ascending colon and proximal 2/3 of transverse colon
- What are the three phases of midgut development?
- elongation & herniation
return of the loop to abdominal cavity
fixation of mesenteries
- Which phase of midgut development is responsible for forming the primary intestinal loop?
- elongation & herniation (phase I)
- What is the apex of the primary intestinal loop attached to?
- yolk sac
- The proximal limb of the primary intestinal loop will form what?
- distal half of the duodenum and the jejunum and ileum
- The distal limb of the primary intestinal loop will form what?
- cecum, ascending colon and 2/3 of transverse colon
- Which limb (proximal/distal) grows faster for the primary intestinal loop?
- During phase 1 which way does the midgut loop rotate? What ist he axis that defines this rotation?
- to the right
- Where do you find blood vessels leading to and draining the gut?
- within the mesentery
- Where is the transverse colon located with respect to the duodenum?
- anterior and transverse to
- What is a subhepatic cecum? Where is the cecum normally located?
- when the cecum fails to descend to the RLQ and remains just under the liver
Normally in RLQ
- What is the SMA between?
- posterior to transverse colon and anterior to 3rd part of duodenum
- Which quadrant is the jejunum located? ileum?
- What forms a diverticulum or bud off the cecum?
- Which limb of the primary intestinal loop forms coils? Which limb retruns first?
- proximal for both
- What is malrotation of the gut? What is there an increased risk of?
- gut didn't rotate normally
chance of necrosis
- Which mesentery is fixed during fixation of the mesenteries?
- What causes the mesenteries to be 2-layered?
- during embryonic folding the right and left side layers of splanchnic mesothelium come together
- Which layer of the mesentery is swept toward the body wall? Is this layer visceral or peritoneal peritoneum?
- right side
- The visceral and peritoneal peritoneums interact to become what?
- fusion fascia
- What is retroperitoneal?
- when an organ is covered on 3 sides or less by visceral peritoneum
- What is a secondarily retroperitoneal organ?
- when an organ starts as intraperitoneal and becomes retroperitoneal
- Name two organs that develop from the start retroperitoneal?
- rectum and kidneys
- What provides a plane for surgical dissection that would avoid invasion of the peritoneal cavity?
- fusion fascia
- Is the pancreas retroperitoneal or intraperitoneal? duodenum?
- both become retroperitoneal
- Which layer of the mesentery (right/left) fuses w/ the peritoneum of the dorsal body wall and fuses the pancreas? Which part of the pancreas is fused?
- left layer
tail of the pancreas
- What replaces the fused peritoneal lyers of the pancreas posteriorly?
- fusion fascia
- When the right layer of the dorsal mesentery fuses with the parietal peritoneum on the dorsal wall which part of the pancreas is fused? Which other organ is at this level?
- head of pancreas
- What is the definitive mesentery to the jejunum and ileum called? Where does it attach in the adult?
- The Mesentery
diagonally along the posterior abdominal wall from the 4th part of duodenum down to R sacroiliac joint
- What is the attachment line of The Mesentery called?
- The SMA travels in the root of the mesentery and between its 2 layers where it arrives at what?
- mesenteric surface (line of attachment) of the jejunum and ileum
- What forms the paracolic gutters? What is their significance?
- fixation causes the depressions in the peritoneum on each side of the ascending and descending colons
the gutters act as conduits for movement of fluid through the peritoneal cavity
- What does the greater omentum fuse to?
- itself and part of the mesentery to the transverse colon
- The resultant mesentery that attaches to the stomach and to the transverse colon is also called what?
- gastrocolic ligament
- What creates the transverse mesocolon?
- fusion of the transverse colon's mesentery proximally to peritoneum overlying the pancreas and duodenum and tot he posterior aspect of the greater omentum
- Is the transverse colon retroperitoneal or intraperitoneal?
- What attaches the transverse colon to the posterior wall?
- hepatic flexure and splenic flexure
- What are the derivatives of the hindgut?
- distal 1/3 of transverse colon, descending and sigmoid colons, rectum and superior part of anal canal
- What is the non-fixed, mobile mesentery of the sigmoid colon called? Is the sigmoid retroperitoneal or intraperitoneal?
- sigmoid mesocolon
- Discuss the peritoneum of the rectum?
- upper 1/3 is covered on 3 sides
middle 1/3 only has peritoneum anteriorly
distal 1/3 has no peritoneum
- What is the vascularture of the large intestine?
- SMA and IMA
- What are the 3 folds of the mesoderm? What do they partition?
separate distal hindgut, or urogenital sinus from the anorectal canal
- What is the dilated junction of the allantois and hindgut?
- What is the cranial-to-caudal migrating mesoderm? This fold will join inferiorly with which other fold?
- Tourneux fold
- What are Rathke folds?
- infolding mesoderm from the left and right sides
- What are the 3 folds of the mesoderm collectively called?
- urorectal septum
- The fusion of uorectal septum with the cloacal membrane divides what two things?
- urogenital membrane and anal membrane
- Proliferation of mesenchyme around the anal membrane and deep to the superficial ectoderm creates what?
- ectodermal proctodeum or anal pit
- The lower 1/3 of the anal canl is lined by what? upper 2/3?
- What is the anatomic junctional zone between the 2 different linings of the anal canal?
- pectinate line
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