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Questions and Answers
The duodenum is initially located in a retroperitoneal position.
The duodenum is initially located in a retroperitoneal position.
False (B)
The celiac trunk supplies blood to the caudal part of the duodenum.
The celiac trunk supplies blood to the caudal part of the duodenum.
True (A)
Duodenal stenosis is a complete occlusion of the lumen.
Duodenal stenosis is a complete occlusion of the lumen.
False (B)
The liver bud develops from the cranial part of the foregut.
The liver bud develops from the cranial part of the foregut.
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The double bubble sign is a characteristic feature of duodenal stenosis.
The double bubble sign is a characteristic feature of duodenal stenosis.
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The liver comprises about 5% of total body weight by the 9th week.
The liver comprises about 5% of total body weight by the 9th week.
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Hematopoiesis in the liver begins during the 8th week.
Hematopoiesis in the liver begins during the 8th week.
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The gall bladder develops from the dorsal bud of the hepatic diverticulum.
The gall bladder develops from the dorsal bud of the hepatic diverticulum.
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Insulin production in the pancreas begins by the 10th week of development.
Insulin production in the pancreas begins by the 10th week of development.
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The spleen develops from the mesoderm within the dorsal mesogastrium.
The spleen develops from the mesoderm within the dorsal mesogastrium.
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Study Notes
Duodenum Development
- The duodenum starts developing early in the 4th week.
- It forms from the caudal part of the foregut and the cranial part of the midgut.
- It rapidly grows into a C-shaped loop projecting ventrally.
- It has a dual arterial supply.
Duodenum Structure
- The duodenum has dual origins, coming from the caudal part of the foregut and cranial part of the midgut.
- It receives a dual blood supply from the coeliac trunk and superior mesenteric artery.
- The opening of the bile duct separates the two parts derived from the foregut and midgut.
- It rapidly grows into a C-shaped loop.
Duodenum Position and Development
- The stomach rotates, moving the duodenum to the right and bringing it into a retroperitoneal position during weeks 5-6.
- The luminal opening during this process closes as the epithelial cells proliferate.
- Recanalization of the duodenum is complete by the end of the embryonic period.
- The ventral mesentery of the duodenum disappears.
Duodenal Defects
- Incomplete recanalization can cause stenosis (narrowing) of the 3rd and 4th parts of the duodenum.
- Complete occlusion of the lumen in the 2nd and 3rd parts of the duodenum can lead to atresia.
- Infants with these defects typically exhibit bile-containing vomiting.
- An X-ray or ultrasound might show a "double bubble" sign.
Canalization Process
- During development, the lumen of the duodenum is initially blocked by an epithelial plug.
- This plug is gradually broken down allowing for canalization.
Liver Development
- The liver appears in the 4th week as a ventral hepatic diverticulum arising from the caudal foregut.
Liver Growth and Size
- The liver rapidly grows during weeks 5-10, occupying much of the abdominal cavity.
- By the 9th week, the liver accounts for about 10% of the total body weight.
- The right and left hepatic lobes are initially of similar size, but the right lobe usually becomes larger later during development.
Liver Cell Development
- Proliferating endodermal cells form hepatic cords, which then anastomose around endothelium-lined spaces called hepatic sinusoids.
Liver Structure and Derivatives
- Hepatic cords and the epithelial lining of the intrahepatic bile system derive from endoderm.
- The fibrous tissue, hematopoietic tissue, and Kupffer cells originate from mesenchyme of the septum transversum.
- Hepatic sinusoids arise from vitelline veins.
- Blood cell formation (hematopoiesis) typically initiates in the liver during the 6th week of development.
- Bile formation begins in the 12th week.
Biliary Apparatus
- The small caudal part of the hepatic diverticulum evolves into the gallbladder.
- The stalk of the diverticulum becomes the cystic duct.
- The stalk connecting the hepatic and cystic ducts forms the bile duct, opening into the duodenum.
Biliary Process
- Bile duct opening is initially obstructed but canalizes later.
- Bile formation starts around the 12th week.
- Bile staining the intestinal contents (meconium) is usually noticeable by the 13th week.
Pancreas Development
- The pancreas develops as two buds (dorsal and ventral) from the caudal foregut.
- The dorsal bud is typically larger and develops first, anterior to the ventral pancreas.
Pancreas Position and Fusion
- During rotation, the ventral and the bile duct moves the ventral bud dorsally.
- The ventral bud is situated posterior to the dorsal bud and eventually fuses with the dorsal bud.
- Their ducts merge to form the main pancreatic duct, which typically empties into the duodenum.
Pancreas Duct Development
- The proximal part of the dorsal duct can persist as a separate accessory pancreatic duct emptying into the duodenum via the minor duodenal papilla.
- The pancreas is retroperitoneal in final position.
Insulin and Glucagon Secretion
- Insulin production begins around the 10th week.
- Glucagon production begins around the 15th week.
Spleen Development
- The spleen develops from mesenchyme within the dorsal mesogastrium and appears in the fifth week of development.
- It develops lobes early in fetal life.
- These lobes normally disappear by birth.
- The spleen plays a critical role in hematopoiesis (blood cell formation) up until late in fetal life, and this ability is maintained through adulthood.
Mesentery Derivatives
- The mesenteries that connect organs to the body wall are important for understanding their development and anatomy.
- The dorsal mesoesophagus becomes the crura of the diaphragm.
- The ventral mesoesophagus disappears.
- The dorsal mesogastrium becomes the greater omentum, lienorenal ligament, and gastrosplenic ligament.
- The ventral mesogastrium becomes the lesser omentum, the visceral peritoneum of the liver, and the falciform ligament.
Anomalies
- Variations in hepatic ducts, cystic ducts, and bile ducts are common but typically not clinically significant.
- Extrahepatic biliary atresia (a blockage of the bile ducts outside the liver) is a serious congenital anomaly that can be life-threatening.
- Accessory or ectopic pancreatic tissue and annular pancreas are other possible congenital abnormalities.
Duodenal/Pancreatic Mesenteries
- The dorsal mesentery of the duodenum persists in the proximal part as the hepatoduodenal ligament.
- The ventral mesentery of the duodenum mostly disappears.
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Description
This quiz covers the development, structure, and position of the duodenum during the embryonic period. Explore its origins, blood supply, and the changes it undergoes as the stomach rotates. Test your knowledge on this crucial aspect of human anatomy.
