Gastrointestinal System Embryology Quiz

Liver: Embryology

• The liver, gallbladder, and biliary duct system arise from the hepatic diverticulum, which develops from embryonic endoderm in the 4th week.
• The hepatic diverticulum extends into the septum transversum, a mass of LP splanchnic mesoderm between the developing heart and midgut, forming the ventral mesentery.
• The liver grows rapidly from the 5th to 10th weeks, filling a large part of the upper abdominal cavity.
• The quantity of oxygenated blood from the umbilical vein determines the development and functional segmentation of the liver.

Development of Liver

• Hematopoiesis begins during the 6th week.
• By the 9th week, the liver accounts for ~ 10% of the total weight of the fetus.
• Bile formation by hepatic cells begins during the 12th week.
• Bile entering the duodenum through the bile duct after the 13th week gives meconium a dark green color.

Clinical Correlates

• Minor variations of liver lobulation are common.
• Congenital anomalies of the liver are rare.
• Variations of the hepatic ducts, bile duct, and cystic duct are common, clinically significant, and may include accessory hepatic ducts.

Gastrointestinal System: Embryology

• The primordial gut at the beginning of the 4th week is closed at the cranial end by the oropharyngeal membrane and at the caudal end by the cloacal membrane.
• The embryonic layers of the primordial gut give rise to epithelia and glands from endoderm and stroma from LP splanchnic mesoderm.
• The primordial gut is divided into three regions: foregut, midgut, and hindgut, each with distinct vascularization.

Foregut Derivatives

• Derivatives of the foregut include the primordial pharynx, oral cavity, teeth, pharynx, tongue, tonsils, salivary glands, upper respiratory system, lower respiratory system, esophagus, stomach, duodenum, liver, and extrahepatic biliary system.

Stomach: Embryology

• Congenital hypertrophic pyloric stenosis is an anomaly of the stomach that affects 1:150 males and 1:750 females.
• The disorder is characterized by a marked thickening of the pyloric sphincter, resulting in severe stenosis of the pyloric canal and obstruction to the passage of food.

Oral Cavity

• The pharyngeal apparatus consists of pharyngeal arches, membranes, pouches, and the omental bursa.
• The omental bursa communicates with the peritoneal cavity through the omental (epiploic) foramen of Winslow.