Development of the gastrointestinal system

Summary

This detailed transcript explores the early stages of human embryonic development, focusing on the formation of the three germ layers: endoderm, mesoderm, and ectoderm. It describes the development of the digestive system, including the formation of the primitive gut tube, which evolves into the stomach, intestines, liver, and pancreas. The video further explains the processes of organ rotation, the formation of digestive structures like the gallbladder and the spleen, and the development of the intestines within the umbilical cord before returning to the abdominal cavity. It concludes with the development of the anus and the urogenital system, offering an in-depth look at early human anatomy.

Takeaways

• 😀 The embryo starts as a flat disc with three germ layers: endoderm, mesoderm, and ectoderm.
• 😀 The yolk sac forms from the endoderm and helps in the development of the digestive system.
• 😀 The primitive gut tube is formed as the embryo folds, separating into three sections: foregut, midgut, and hindgut.
• 😀 The foregut gives rise to the upper digestive tract, including the esophagus, liver, pancreas, and lungs.
• 😀 The midgut develops into parts of the small intestine and large intestine, including the appendix, ascending colon, and part of the transverse colon.
• 😀 The hindgut develops into the descending colon, sigmoid colon, and upper anal canal.
• 😀 The stomach undergoes a 90° clockwise rotation during its development, creating the greater and lesser curvatures.
• 😀 The liver, gallbladder, and pancreas all develop from the foregut endoderm, with the pancreas starting to secrete insulin by week 10.
• 😀 The midgut herniates into the umbilical cord around week 6, completing its rotation and returning to the abdominal cavity by week 10.
• 😀 The hindgut and midgut are separated by the urorectal septum, forming the urogenital sinus and anal canal, with the anal canal opening by week 7.

Q & A

What are the three germ layers of the embryo during week three?

The three germ layers of the embryo during week three are the endoderm, mesoderm, and ectoderm.

What is the yolk sac, and what role does it play during embryonic development?

The yolk sac is a fluid-filled bubble that forms from the endoderm (belly side) of the embryo. It grows alongside the developing embryo and plays a role in the early development of the digestive system.

What is the primitive gut tube, and how does it form?

The primitive gut tube forms when the embryo folds along its vertical and horizontal axes. This folding creates a tubular organism, which pinches the yolk sac and incorporates part of it inside, eventually forming the primitive gut tube.

What are the three parts of the primitive gut, and what arteries supply them?

The three parts of the primitive gut are the foregut, midgut, and hindgut. The foregut is nourished by the celiac artery, the midgut by the superior mesenteric artery, and the hindgut by the inferior mesenteric artery.

How does the stomach rotate during embryonic development, and what does this affect?

The stomach undergoes a 90° clockwise rotation along its length during development. This rotation moves the greater curvature to the left side of the body and the lesser curvature to the right side, giving the stomach an anterior and posterior face.

What are the roles of the dorsal and ventral mesogastrium in stomach development?

The dorsal mesogastrium anchors the stomach to the posterior body wall, forming the greater curvature. The ventral mesogastrium anchors the stomach to the anterior body wall, forming the lesser curvature and eventually developing into the lesser omentum.

What is the role of the hepatic diverticulum in liver development?

The hepatic diverticulum, also known as the liver bud, forms inside the ventral mesogastrium and extends into the septum transversum. It gives rise to the liver, gallbladder, and biliary duct system.

How does the pancreas develop during embryogenesis?

The pancreas develops from two buds: the ventral bud and the dorsal bud. These buds eventually unite to form the pancreas, with the dorsal bud forming the body, tail, and most of the pancreatic head, while the ventral bud contributes to the rest of the pancreatic head.

What is physiological gut herniation, and when does it occur?

Physiological gut herniation is when the primary intestinal loop herniates through the vitelline duct and develops inside the umbilical cord. This occurs around week 6 and lasts until week 10, as the embryo's abdominal cavity becomes too small to hold the growing intestines.

What is the significance of the urorectal septum during development?

The urorectal septum forms during week four and separates the cloaca into an anterior urogenital sinus and a posterior anal canal. This division is crucial for proper separation of the urinary, genital, and digestive systems, and the separation is completed by week seven.