Digestive System Development Lecture 1

Questions and Answers

What forms the gut tube during the 3rd and 4th weeks of embryonic development?

Neural plate forming

Endoderm rolling down (correct)

Mesoderm rolling down

Ectoderm rolling down

Which layers make up the trilaminar embryonic disc?

Ectoderm, endoderm, and visceral layer

Ectoderm, endoderm, and mesoderm (correct)

Endoderm, mesoderm, and parietal layer

Ectoderm, telectoderm, and endoderm

What type of organ possesses mesenteries?

Retroperitoneal organs

Intraperitoneal organs (correct)

Parietal organs

Somatic organs

What do the cephalocaudal and lateral folding of the embryo form?

Primitive gut tube Signup and view all the answers

Which layer of the embryonic disc is responsible for forming the brain and spinal cord?

Ectoderm Signup and view all the answers

What is the space between the visceral and somatic layers of lateral plate mesoderm called?

Primitive body cavity Signup and view all the answers

What are the blind-ending tubes formed at the cephalic and caudal parts of the embryo called?

Foregut and hindgut Signup and view all the answers

What is the fate of the embryonic dorsal mesenteries?

They become part of the abdominal wall Signup and view all the answers

What connects the midgut to the yolk sac during development?

Vitelline duct Signup and view all the answers

Which process is involved in the division of the gut tube?

Transverse folding Signup and view all the answers

Which type of organs are covered by peritoneum on their anterior surface only?

Retroperitoneal organs Signup and view all the answers

What is the function of mesenteries and ligaments in the abdominal cavity?

To supply pathways for vessels, nerves, and lymphatics Signup and view all the answers

What is the dorsal mesentery divided into?

Dorsal mesogastrium, dorsal mesoduodenum, dorsal mesocolon, and mesentery proper Signup and view all the answers

Where does the ventral mesentery primarily exist?

In the region of the foregut and upper part of the duodenum Signup and view all the answers

What develops at the ventral wall of the foregut?

Respiratory diverticulum (lung bud) Signup and view all the answers

What structure gradually partitions the respiratory diverticulum from the dorsal part of the foregut?

Tracheoesophageal septum Signup and view all the answers

What does the mesoderm of the septum transversum primarily form?

Hematopoietic cells Signup and view all the answers

Which structure does NOT cover the surface of the liver?

Central tendon of the diaphragm Signup and view all the answers

What is the likelihood of surviving extrahepatic biliary atresia without a liver transplant?

80% to 85% Signup and view all the answers

Which of the following structures is formed from the mesoderm on the surface of the liver?

Visceral peritoneum Signup and view all the answers

What is the rare abnormality associated with intrahepatic biliary duct atresia?

Fetal infections Signup and view all the answers

Which statement is true regarding the source of both the respiratory and digestive systems?

Both systems develop from the endoderm. Signup and view all the answers

What characterizes the muscular coat of the esophagus?

It is striated in its upper two-thirds and smooth in the lower third. Signup and view all the answers

What causes congenital hiatal hernia?

Insufficient lengthening of the esophagus. Signup and view all the answers

During what week does the stomach appear as a fusiform expansion of the foregut?

4th week. Signup and view all the answers

What occurs during the stomach's rotation around its longitudinal axis?

The stomach rotates 90° clockwise. Signup and view all the answers

What is the position of the pyloric part of the stomach after rotation?

Moves to the right and upward. Signup and view all the answers

What effect does the disproportionate growth of the stomach have on the mesenteries?

It alters the positions of dorsal and ventral mesogastrium. Signup and view all the answers

Which nerve innervates the anterior wall of the stomach?

Left vagus nerve. Signup and view all the answers

What connects the spleen to the stomach?

Gastrolienal ligament Signup and view all the answers

What is the likely cause of pyloric stenosis in infants?

Hypertrophy of the longitudinal musculature in the stomach Signup and view all the answers

Which artery supplies the foregut?

Celiac artery Signup and view all the answers

At what stage does the liver primordium first appear?

Middle of the third week of development Signup and view all the answers

What significant change occurs in the duodenum as the stomach rotates?

It takes on a C-shaped loop formation Signup and view all the answers

Which of the following is NOT a typical abnormality of the stomach?

Herniation Signup and view all the answers

What is the fate of the posterior leaf of the dorsal mesogastrium during spleen development?

It degenerates Signup and view all the answers

What structure differentiates into the lining of the biliary ducts and gall bladder in the liver?

The hepatic cords Signup and view all the answers

Study Notes

Learning Outcomes

Understand embryonic folding processes that create the primitive gut and abdominal wall during the 3rd and 4th week.
Describe the development of pregut derivatives.
Explain the development of the coelomic and peritoneal cavities.
Discuss the fates of embryonic dorsal and ventral mesenteries.
Recognize why some abdominal organs have mesenteries while others are retroperitoneal.
Understand the positioning of the viscera and developmental causes of congenital gastrointestinal defects.

Embryonic Folding

During the 3rd and 4th weeks, ectoderm forms the neural plate, which rolls into the neural tube via neurulation.
The endoderm rolls down to form the gut tube, resulting in a tube-on-a-tube structure: neural tube dorsally and gut tube ventrally.
Mesoderm holds the two tubes together and splits into visceral and somatic layers, forming the lateral body wall.

Gut Tube Formation

Cephalocaudal and lateral folding create the primitive gut tube.
The primitive gut divides into foregut (cephalic), midgut (connected to yolk sac), and hindgut (caudal).

Mesenteries and Organ Suspension

Mesenteries (peritoneum) suspend some gut portions from the dorsal and ventral body wall.
Intraperitoneal organs are enclosed by double layers of peritoneum, connecting them to the body wall.
Retroperitoneal organs, such as kidneys, lie against the posterior wall with peritoneum only on the anterior surface.

Dorsal and Ventral Mesentery Development

The dorsal mesentery extends from the lower end of the esophagus to the cloacal region.
Dorsal mesogastrium forms the greater omentum; dorsal mesoduodenum and dorsal mesocolon also develop from the dorsal mesentery.
Ventral mesentery originates from the septum transversum and gives rise to the lesser omentum and falciform ligament.

Foregut Development

The respiratory diverticulum appears at the foregut's ventral wall, with the tracheoesophageal septum separating it from the dorsal foregut.
The esophagus rapidly lengthens, with varying muscular innervation: striated upper 2/3 by the vagus and smooth lower third by the splanchnic plexus.

Clinical Correlates: Esophageal Abnormalities

Esophageal atresia/tracheoesophageal fistula develops from anomalies during septum formation.
Esophageal stenosis primarily occurs in the lower third, linked to incomplete recanalization or vascular abnormalities.
Congenital hiatal hernia results from insufficient esophageal lengthening, pulling the stomach into the diaphragm.

Stomach Development

The stomach appears as a fusiform expansion of the foregut by the 4th week.
It undergoes 90° clockwise rotation around its longitudinal axis, altering the positions of its anterior and posterior walls.
Stomach rotation creates the omental bursa and affects mesogastrium position; the dorsal mesogastrium lengthens while the ventral moves right.

Stomach Abnormalities

Pyloric stenosis arises from hypertrophy of the pyloric musculature, causing severe food passage obstruction in infants.
Other rare stomach malformations include duplications and prepyloric septums.

Duodenum Development

Formed from the terminal foregut and cephalic midgut, the duodenum rotates into a C-shape during stomach development, becoming retroperitoneal.

Liver Development

The liver primordium appears in the 3rd week as an outgrowth from the endoderm at the foregut's distal end.
Liver cords differentiate into functional liver cells and structures for the biliary system, mixing with vitelline and umbilical veins.

Septum Transversum Contributions

Mesoderm of the septum transversum forms hepatocytes, Kupffer cells, connective tissues, peritoneum of the liver, falciform ligament, lesser omentum, and central tendon of the diaphragm.

Bare Area of the Liver

The liver's cranial surface remains uncovered by peritoneum, termed the bare area, while the rest is enveloped in visceral peritoneum.

Clinical Correlates: Biliary Atresia

Extrahepatic biliary atresia has low correctable defect rates, with most untreated cases leading to mortality without transplants.
Intrahepatic biliary duct atresia is a rare condition possibly linked to fetal infections, occurring in about 1 in 100,000 live births.

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Description

This quiz covers the development of the digestive system during embryonic stages, focusing on the formation of the primitive gut and abdominal wall. Understand key processes that occur in the 3rd and 4th week of embryogenesis, as well as the development of coelomic and peritoneal cavities.