Embryology: Allantois and Cloaca Formation

Questions and Answers

What significant structure does the allantois contribute to in embryonic development?

Development of the umbilical cord

Formation of the respiratory diverticulum

Development of the pharyngeal gut

Formation of the cloaca (correct)

At what point in embryonic development is the respiratory diverticulum first visible?

Six weeks

Five weeks

Four weeks (correct)

Three weeks

Which structure is primarily responsible for the partitioning of the foregut?

Connecting stalk

Somatic mesoderm

Tracheoesophageal septum (correct)

Allantois

The foregut includes which of the following derivatives?

Liver and pancreas Signup and view all the answers

Which embryonic layer does the hindgut primarily derive from?

Endoderm Signup and view all the answers

Which embryonic structure is formed at the caudal end of the gastrointestinal tract?

Proctodeum Signup and view all the answers

What occurs by Day 35 in the context of the connecting stalk in embryonic development?

It fuses with the yolk sac stalk to form the umbilical cord Signup and view all the answers

Which structure is NOT a derivative of the foregut?

Proximal large intestine Signup and view all the answers

What structure partitions the cephalic foregut, including the esophagus?

Tracheoesophageal septum Signup and view all the answers

Which statement accurately describes the muscular composition of the upper two-thirds of the esophagus?

It is striated muscle formed from surrounding visceral mesenchyme. Signup and view all the answers

What consequence results from the faster growth of the dorsal wall of the stomach compared to the ventral wall?

Development of greater and lesser curvature Signup and view all the answers

During the rotation of the stomach, which direction does the ventral surface rotate?

To the right Signup and view all the answers

What happens to the left side of the stomach during its development?

It becomes the ventral surface. Signup and view all the answers

At what stage of embryonic development does the tracheoesophageal septum initially begin to partition the foregut?

4 weeks Signup and view all the answers

What is the approximate frequency of the most common type of esophageal atresia?

90% Signup and view all the answers

In the context of gastric development, what is indicated by the caudal region moving superiorly and to the right?

Transverse positioning of the stomach Signup and view all the answers

Which expression is known to upregulate factors in the mesoderm that contribute to the differentiation of the gut tube structures?

SHH Signup and view all the answers

What is the percentage associated with congenital cardiac anomalies in cases of omphalocele?

50% Signup and view all the answers

What is the consequence of the midgut loop failing to return to the abdominal cavity by week 11 of development?

Omphalocele Signup and view all the answers

What is the incidence rate of omphalocele at birth?

2.5/10,000 births Signup and view all the answers

Which structure is formed as a continuous serous membrane lining the inner surface of the abdominal cavity?

Peritoneum Signup and view all the answers

Which of the following factors is NOT associated with an increased risk of omphalocele?

Pancreatitis Signup and view all the answers

During which week of embryonic development does the midgut loop typically herniate through the primitive umbilical ring?

Week 6 Signup and view all the answers

What type of gastrointestinal defect can result in obstruction due to twisting of intestinal loops?

Gut rotation defects Signup and view all the answers

Which condition is characterized by a defect in the abdominal wall resulting in protrusion of abdominal contents?

Gastroschisis Signup and view all the answers

Which of the following statements about gut rotation in normal anatomy is correct?

It rotates 270° counterclockwise. Signup and view all the answers

Which of the following factors is primarily involved in determining the structure that forms from the gut tube?

HOX Signup and view all the answers

What potential consequence may occur due to malrotation of intestinal loops?

Twisting of the intestine Signup and view all the answers

What developmental issue may arise if intestinal loops fail to return by a specific week during embryogenesis?

Gastroschisis Signup and view all the answers

Which of the following conditions is not directly associated with developmental defects of the gastrointestinal tract in embryonic development?

Cleft lip Signup and view all the answers

Which abnormality can occur due to an umbilical fistula?

Fecal discharge at the umbilicus Signup and view all the answers

What defines gastroschisis?

Protrusion of abdominal contents through the body wall directly into the amniotic cavity Signup and view all the answers

What anatomical structure results from the obliteration of the bile duct?

Distention of the gallbladder and hepatic ducts Signup and view all the answers

Which factors are involved in the molecular regulation of pancreas development?

FGF2 and Activin Signup and view all the answers

What gene is upregulated as a result of repression of SHH in the endoderm?

PDX Signup and view all the answers

Which pancreatic structure is primarily derived from the dorsal pancreatic bud?

Rest of the gland Signup and view all the answers

What does the ventral pancreatic bud develop to form?

Uncinate process and inferior pancreatic head Signup and view all the answers

What role do the paired homeobox genes PAX4 and PAX6 play in pancreas development?

They specify the endocrine cell lineage. Signup and view all the answers

How is the main pancreatic duct formed?

From the merging of dorsal and ventral pancreatic ducts Signup and view all the answers

What happens to the proximal part of the dorsal pancreatic duct during development?

It is obliterated or may persist as a small channel. Signup and view all the answers

Study Notes

Allantois and Umbilical Cord Formation

Allantois develops into the cloaca.
By four weeks, the connecting stalk and yolk sac stalk fuse, forming the umbilical cord.
The distal allantois remains in the connecting stalk, originating at the foregut's ventral wall.

Primitive Gut Structure

Stomodeum (ectoderm) located at the cranial end of the gut.
Foregut, midgut, and hindgut consist of endoderm and splanchnic mesoderm.
Proctodeum (anal pit) is at the caudal end, composed of ectoderm.

Derivatives of the Foregut

Forms important structures: pharynx, esophagus, stomach, duodenum (proximal to bile duct), liver, biliary system, and pancreas.
The partitioning of the foregut begins at four weeks with the tracheoesophageal septum.

Esophagus Development

Initially short, lengthens as the heart and lungs descend.
Upper two-thirds of the esophagus is striated muscle, formed by surrounding visceral mesenchyme, influenced by the vagus nerve.

Stomach Development

Dorsal wall grows faster than the ventral wall, creating the greater and lesser curvature.
Stomach rotation involves moving the ventral surface to the right and the dorsal border to the left, changing the long axis to near transverse orientation.

Pancreas Formation

Develops from two pancreatic buds: the dorsal bud in the dorsal mesentery and the ventral bud near the bile duct.
FGF2 and Activin from the notochord regulate pancreas development.
The ventral bud relocates dorsally during the rotation of the duodenum.

Midgut Development

Midgut is suspended by the vitelline duct, which transforms into fibrous cords during Week 5.
Omphalocele and gastroschisis are associated with abnormal midgut development.

Gut Rotation Defects

Malrotation can lead to volvulus, compromising blood supply.
Normal rotation of the primary intestinal loop is 270° counterclockwise.

Associated Anomalies

Omphalocele and gastroschisis are defects involving abdominal contents.
Risk factors for omphalocele include alcohol, tobacco, SSRI use, and obesity.

Peritoneum

Continuous serous membrane lining the abdominal cavity, reflected onto the viscera.

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Description

Explore the development of the allantois and its role in forming the cloaca during embryonic stages. This quiz discusses the connecting stalk's fusion and the respiratory diverticulum. Test your knowledge on crucial embryological concepts and their timelines.