Midgut and Hindgut Flashcards
What artery supplies the midgut? What organs are part of the midgut?
Superior mesenteric artery
3rd, 4th parts of the duodenum, jejunum, ileum, part of the pancreas, cecum, appendix, ascending colon and proximal 2/3 of the transverse colon
What artery supplies the hindgut? What organs are part of the hindgut?
Inferior mesenteric artery
Distal 1/3 of the transverse colon, descending colon, sigmoid colon, rectum.
What is the duodenum shaped like? Where is the division between the foregut and midgut located?
Shaped like a G. The division is located roughly in the middle of the 2nd, vertical portion of the G.
Describe the blood supply to the pancreas.
The splenic artery (off the celiac trunk) traverses the superior part of the pancreas and sends out branches to supply the body and tail.
The head is supplied by the anterior and posterior superior pancreatico-duodenal arteries (branches of the gastroduodenal a.), which anastomose with the anterior and posterior branches of the inferior pancreatico-duodenal arteries (off the superior mesenteric a.).
If the superior mesenteric artery were occluded, how would the pancreas get blood?
From the posterior and anterior superior pacreatico-duodenal arteries (from the gastroduodenal a.)
The duodenum is a ________ structure and the rest of the small intestine is __________. The junction between them (duodenojejeunal junction) is
marked by the ligament of ______, which connects the ________ _______ to the _______ ______.
the duodenum is a retroperitoneal structure and the rest of the small intestine is intraperitoneal.
The ligament of Treitz marks the junction between the duodenum and jejunum and connects the small intestine to the right crus
What are the mucosal folds in the lumen of the small intestine called?
Plicae circulares
What is different about the vasa recta and arcades that supply the jejunum vs the vasa recta and arcades that supply the ileum?
Vasa recta are longer in the proximal small intestine, and distally the arcades become more complex and vasa recta get shorter.
The superior mesenteric artery descends and crosses anteriorly to the third part of the _________ (a potential place for intestinal constriction - SMA syndrome). Describe the arteries that branch off the SMA to supply the small intestine.
SMA crosses the 3rd part of the duodenum.
Arteries shoot off the SMA, arcades connect those together, and vasa recta shoot off the arcades to supply the small intestine.
What is superior mesenteric artery syndrome? What are the clinical signs and symptoms?
Compression of the 3rd part of the duodenum by the SMA (aneurysm or congenital defect). Causes BILIOUS vomiting, dilation of the 1st and 2nd parts of the duodenum. It may also compress the renal vein.
What is pyloric stenosis and what are the clinical features (6)?
Stenosis of the pyloric sphincter (separates stomach from duodenum). Causes abdominal pain, stomach distension, dehydration, electrolyte imbalance, failure to gain weight, and NON-BILIOUS projectile vomiting.
Why is the right vagus nerve found posteriorly on the stomach and the left found anteriorly?
As the stomach developed, it rotated anteriorly and to the right.
LARP
Describe how the spleen develops within the dorsal mesentery (greater omentum) and how the ligaments that connect the spleen to the kidney and stomach come to be.
As the stomach rotates anteriorly and to the right, the dorsal mesentery stretches out. The spleen develops in the middle of this mesentery. Once developed, the mesentery that remains on either side of the spleen forms ligaments.
The mesentery coming off the anterior spleen is still connected to the stomach - called the gastrolienal ligament.
The mesentery coming off the posterior fuses with the left kidney - called the lienorenal ligament.
As the greater omentum (dorsal mesogastrium) grows downwards, it fuses with the mesentery of the ________ _______.
transverse colon
How does the pancreas develop?
From two buds near the major duodenal papilla (of Vater). One bud starts in the ventral mesogastrium where the liver first started developing. This rotates behind and around the duodenum to form the main pancreatic duct, uncinate process and part of the pancreatic head.
The other bud starts in the dorsal mesogastrium and forms the accessory pancreatic duct, body, tail, and part of the head.
Islets of Langerhans form from pancreatic parenchyma in the third month, which is derived from _______. Insulin secretion begins in the 5th month. Pancreatic CT is derived from _______ _______.
Islets are derived from endoderm.
CT is derived from splanchnic mesoderm
Is the pancreas fused to the posterior abdominal wall? What is that called?
Yeah, it fuses after it develops from the dorsal and ventral mesogastrium - called secondarily retroperitoneal.
What is an annular pancreas? What are the clinical features?
When the developing pancreatic buds grow and rotate in opposite directions to engulf the duodenum –> constriction. Symptoms are feeding intolerance, BILIOUS vomiting, and abdominal distension.
Name the disease(s) that cause bilious vomiting and the disease(s) that cause non-bilious vomiting.
Bilious: annular pancreas and superior mesenteric artery syndrome
Non-bilious: congenital hypertrophic pyloric stenosis
What is the vitelline duct connected to during development?
The apex of the primary intestinal loop.
What is physiological umbilical herniation? What does the cephalic limb go on to form? what about the caudal limb?
It is when the primary intestinal loop herniates into the extraembryonic cavity so it can develop. The cephalic limb becomes the rest of the duodenum, jejunum, and part of the ileum. The caudal limb becomes the rest of the ileum, cecum, appendix, ascending colon, and proximal 2/3 of the transverse colon.
How does a subhepatic appendix develop?
The cecum is the last part of the developing midgut to return back from the extraembryonic cavity, at which point it lies directly below the liver. Failure to descend after this point –> suphepatic appendix.
What is Meckel’s diverticulum?
An ileal diverticulum formed from failure of the vitelline duct (yolk stalk) to regress completely once the midgut retracts back into the abdomen during development.
