Development of Duodenum (Dr Dosumu) PDF

# Development of the Duodenum - Duodenum begins to develop early in the 4th week, from the caudal part of the foregut and the cranial part of the midgut. - It grows rapidly, forms a C-shaped loop that projects ventrally. - The duodenum has dual arterial supply. - Caudal part of the foregut. -...

# Development of the Duodenum - Duodenum begins to develop early in the 4th week, from the caudal part of the foregut and the cranial part of the midgut. - It grows rapidly, forms a C-shaped loop that projects ventrally. - The duodenum has dual arterial supply. - Caudal part of the foregut. - Cranial part of the midgut. - The duodenum has dual blood supply from the celiac trunk and superior mesenteric artery. - The opening of the bile duct separates the two parts derived from the foregut and the midgut. - The duodenum grows rapidly to form a C-shaped loop. - Rotation of the stomach pulls it to the right, bringing it to a retroperitoneal position. - During the 5th-6th weeks, its lumen obliterates due to the proliferation of epithelial cells. - Recanalization is complete by the end of the embryonic period. - Most of the ventral mesentery disappears by this time. - Initially ventral, it then rotates to the right during the rotation of the stomach. - The duodenum loses its dorsal mesentery, becoming retroperitoneal. - During the 5th-6th week the lumen is obliterated. - During the 8th week the lumen is recanalized. - The ventral mesentery disappears. ## Development of Duodenum Diagram The diagram shows the development of the duodenum and pancreas: 1. The duodenum is shown as a loop with a dorsal and ventral pancreas. 2. The duodenum rotates to the right, bringing it to a retroperitoneal position. 3. The dorsal and ventral pancreas fuse together. # Congenital Abnormalities - **Duodenal stenosis**: incomplete recanalization involves the 3rd and 4th parts of the duodenum. - **Duodenal atresia**: complete occlusion of the lumen involves the 2nd and 3rd parts of the duodenum. - Clinical presentation is bilous vomiting in infants. - The "double bubble" sign on X-ray or USS. ## Process of Canalization Diagram The diagram shows the process of canalization: 1. A solid epithelial plug is present in the duodenum at the level of section C1 2. Vacuoles appear in the epithelial plug at the level of section D1. 3. Recanalization occurs at the level of D1. 4. The lumen is normal at the level of section D3 The diagram also shows an ultrasound image of a "double bubble" sign, which is a characteristic feature of duodenal atresia. # Development of the Liver - The liver appears in the 4th week as a ventral bud called the hepatic diverticulum, from the caudal part of the foregut. - The liver grows rapidly and in 5-10th weeks fills a large part of the abdominal cavity. - The liver forms about 10% of total body weight by the 9th week. - The right and left lobes of the liver are initially the same size but later the right lobe grows larger. - The proliferating endodermal cells give rise to hepatic cords which anastomose around endothelium lined spaces - hepatic sinusoids. - The hepatic cords and the epithelial lining of the intrahepatic portion of the biliary system is derived from the endoderm, while the fibrous tissue, hematopoietic tissue and kupffer cells are derived from the mesenchyme of the septum transversum. - The hepatic sinusoids are derived from vitelline veins. - Hematopoiesis begins during the 6th week, giving a dark color to the liver. - Hepatic cells begin to form bile during the 12th week. # Development of the Biliary Apparatus - The small caudal part of the hepatic diverticulum becomes the gall bladder and the stalk of the diverticulum forms the cystic duct. - The stalk connecting the hepatic & cystic ducts to the duodenum becomes the bile duct and opens on the ventral aspect of the duodenum. - Later due to rotation of the duodenum, the opening of the bile duct comes to lie dorsally. - The ducts become occluded initially but are later canalized. - Bile formation commences about the 12th week. - After the 13th week, bile entering the duodenum gives a dark green color to the intestinal content (meconium). # Development of the Pancreas - The pancreas begins to appear as two buds, dorsal and ventral, from the caudal part of the foregut. - The dorsal bud is larger, appears first, and lies cranial to the smaller ventral bud. - The rotation of the stomach and duodenum carry the ventral bud dorsally along with the bile duct. - The ventral bud comes to lie post to the dorsal bud and their ducts anastomose. - The duct of the ventral bud and the distal part of the duct of the dorsal bud form the main pancreatic duct that opens on the major duodenal papilla. - The proximal part of the duct of the dorsal bud often persists as the accessory pancreatic duct that opens separately on the minor duodenal papilla. - The dorsal bud forms most of the pancreas. - The ventral bud gives rise to the uncinate process and part of the head of the pancreas. - The pancreas comes to lie horizontally along the posterior abdominal wall in a retroperitoneal position. - Insulin production begins in the 10th week. - Glucagon production begins in the 15th week. # Spleen Development - The spleen develops from the mesenchyme within the dorsal mesogastrium. - It begins to develop in the 5th week and attains its shape early in fetal life. - The spleen is lobulated initially, but the lobules normally disappear before birth. - The spleen functions as a hematopoietic organ until late fetal life, but retains its potential for blood cell formation even in adult life. # Derivatives of the Mesenteries of the Foregut - **Dorsal Mesoesophagus**: crura of the diaphragm - **Ventral Mesoesophagus**: disappears completely - **Dorsal Mesogastrium**: - Greater omentum - Lienorenal ligament - Gastrosplenic ligament - **Ventral Mesogastrium**: - Lesser omentum - Visceral peritoneum of the liver. - Falciform ligament of the liver - **Dorsal mesentery of the duodenum**: persists in the proximal part (one inch) as hepatoduodenal ligament. - **Ventral mesentery of the duodenum**: disappears almost completely. # Anomalies Related to the Development of the Liver & Gall Bladder - Anomalies of the liver are rare. - Variations in hepatic ducts, cystic and bile ducts are common and clinically significant. - **Extrahepatic biliary atresia**: the most common serious anomaly. Jaundice develops soon after birth. If uncorrected surgically leads to death. # Anomalies Related to the Development of the Pancreas - **Accessory/Ectopic pancreatic tissue** - **Annular pancreas tissue** ## Congenital Anomalies of Pancreas Diagram The diagram shows three types of pancreatic anomalies: 1. "Bifid ventral pancreatic bud" - The ventral pancreatic bud is split into two, with one part passing dorsal to the duodenum and pancreas. 2. "Annular pancreas" - The ventral pancreatic bud forms a ring around the duodenum, potentially causing obstruction.