2. note provides a detailed summary of the development and formation of the gut system in embryonic development.
Here are the key points discussed:
1. Divisions of the Gut: The gut system is divided into four regions: the Pharyngeal gut, foregut, midgut, and hindgut.
Each region gives rise to specific structures and organs.
2. Derivatives: The endoderm gives rise to the epithelial lining of the digestive tract and glandular structures, while
the visceral mesoderm contributes to connective tissue, muscular components, and peritoneal components of the
gut.
3. Molecular Regulation of Gut Development: The regional specification of the gut tube is influenced by interactions
between the gut endoderm and the surrounding mesoderm. Retinoic acid and HOX genes play important roles in the
differentiation and organization of the gut and its derivatives.
4. Mesentery: The gut is supported by the mesentery, which is a double layer of peritoneum. The dorsal mesentery
extends from the esophagus to the rectum, providing a pathway for blood vessels, lymphatics, and nerves. The
ventral mesentery, including the lesser omentum and falciform ligament, is derived from the septum transversum
and is continuous with the dorsal mesentery.
5. Development of Specific Organs:
- Oesophagus: The oesophagus develops from the foregut and consists of striated and smooth muscles.
- Stomach: The stomach forms as a dilatation near the respiratory diverticulum and undergoes rotational growth,
resulting in the formation of greater and lesser curvatures.
- Liver and Gallbladder: The liver develops as an outgrowth from the foregut, and the gallbladder forms as a
3. 3. Molecular Regulation of Gut Development: The regional specification of the gut tube is influenced by interactions
between the gut endoderm and the surrounding mesoderm. Retinoic acid and HOX genes play important roles in the
differentiation and organization of the gut and its derivatives.
4. Mesentery: The gut is supported by the mesentery, which is a double layer of peritoneum. The dorsal mesentery extends
from the esophagus to the rectum, providing a pathway for blood vessels, lymphatics, and nerves. The ventral mesentery,
including the lesser omentum and falciform ligament, is derived from the septum transversum and is continuous with the
dorsal mesentery.
5. Development of Specific Organs:
- Oesophagus: The oesophagus develops from the foregut and consists of striated and smooth muscles.
- Stomach: The stomach forms as a dilatation near the respiratory diverticulum and undergoes rotational growth, resulting
in the formation of greater and lesser curvatures.
- Liver and Gallbladder: The liver develops as an outgrowth from the foregut, and the gallbladder forms as a ventral
outgrowth of the bile duct. The hepatic cells differentiate within the septum transversum.
- Pancreas: The pancreas develops from ventral and dorsal buds originating from the endodermal lining of the duodenum.
The buds fuse to form the pancreas, which produces insulin and digestive enzymes.
- Midgut: The midgut extends from the duodenum to the proximal 2/3 of the transverse colon and undergoes herniation
and rotation during development.
- Hindgut: The hindgut extends from the distal 1/3 of the transverse colon to the cloacal membrane and gives rise to the
lower part of the gastrointestinal tract.
