Embryology L7: Gut Tube and Body Cavities

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Questions and Answers

What do the pleuroperitoneal membranes fuse with during diaphragm development?

Pectoral muscles

Esophageal muscles

Mesentery of the esophagus (correct)

Phrenic nerves

From which cervical segments do the muscle cells of the diaphragm originate?

C2—C4

C4—C6

C3—C5 (correct)

C1—C3

What is the primary function of the phrenic nerves in relation to the diaphragm?

Control digestion

Support spinal column stability

Provide blood supply

Innervate diaphragm for motor and sensory functions (correct)

What is the main consequence of differential growth during the sixth week of embryo development?

The diaphragm moves ventrally and caudally (C) Signup and view all the answers

Which structure is NOT directly involved in the formation of the diaphragm?

Pulmonary arteries (C) Signup and view all the answers

What is the primary origin of the septum transversum?

Visceral mesoderm (D) Signup and view all the answers

What do the pericardioperitoneal canals become as lung buds grow?

Pleural cavities (A) Signup and view all the answers

Which structures fuse to form the fibrous pericardium in adults?

Pleuropericardial membranes (D) Signup and view all the answers

How does the thoracic cavity divide into definitive compartments?

Via the separation of pleural and pericardial cavities (D) Signup and view all the answers

What is the role of the pleuroperitoneal folds during development?

To close the pericardioperitoneal canals (A) Signup and view all the answers

What tissue gives rise to the definitive wall of the thorax?

Somatic mesoderm (A) Signup and view all the answers

What embryological change causes the enlargement of the pleuropericardial folds?

Lung expansion (A) Signup and view all the answers

What do the pleuropericardial membranes contain?

Phrenic nerves and common cardinal veins (D) Signup and view all the answers

What does the ectoderm layer form during the third and fourth weeks of embryonic development?

Neural tube (A) Signup and view all the answers

Which layer of the embryonic disc is primarily responsible for forming the gut tube?

Endoderm (C) Signup and view all the answers

What is the term for the space between the visceral and parietal layers of lateral plate mesoderm?

Primitive body cavity (C) Signup and view all the answers

At the end of the third week of embryonic development, what does the lateral plate mesoderm differentiate into?

Paraxial, intermediate, and lateral plate mesoderm (A) Signup and view all the answers

Which structure forms the somatopleure?

Parietal layer of mesoderm and overlying ectoderm (C) Signup and view all the answers

What occurs to the lateral plate mesoderm during the formation of the body cavity?

Clefts appear and coalesce, splitting it into two layers (C) Signup and view all the answers

Which layer is intimately connected to the gut tube?

Visceral mesoderm (A) Signup and view all the answers

What is the role of the intermediate mesoderm during embryonic development?

Contribution to the urogenital system (B) Signup and view all the answers

What structures begin to form the lateral body wall folds in the embryo during the fourth week?

Parietal layer of lateral plate mesoderm (B) Signup and view all the answers

Which region does not undergo closure of the ventral body wall?

Connecting stalk (C) Signup and view all the answers

What structure is formed from the endoderm layer folding ventrally during the fourth week?

Gut tube (D) Signup and view all the answers

What happens to the Vitelline duct between the second and third months of gestation?

It degenerates with the yolk sac (A) Signup and view all the answers

What do the cells of the parietal layer of lateral plate mesoderm develop into?

Mesothelial cells forming parietal serous membranes (A) Signup and view all the answers

Where is the dorsal mesentery located in relation to the gut tube?

Extends from the foregut to the hindgut (C) Signup and view all the answers

What is the role of the ventral mesentery?

To provide structural support for the diaphragm (D) Signup and view all the answers

Which of the following statements about visceral and parietal layers of mesoderm is NOT true?

Parietal layers are only found on the exterior of the body cavity. (D) Signup and view all the answers

Study Notes

Embryology L7: The Gut Tube and Body Cavities

The gut tube forms during the third and fourth weeks of development.
The neural tube forms simultaneously, creating a tube-on-a-tube structure for the embryo.
The mesoderm layer holds the neural tube and gut tube together with its visceral (splanchnic) and parietal (somatic) components.
The visceral layer is connected to the gut tube.
The parietal layer forms the lateral body wall folds.
The space between the visceral and parietal layers is the primitive body cavity, which is initially continuous.
The primitive body cavity eventually develops into the pericardial, pleural, and abdomino-pelvic regions.

Formation of the Body Cavity

At the end of the third week, intraembryonic mesoderm differentiates into paraxial, intermediate, and lateral plate mesoderm.
Paraxial mesoderm forms somitomeres and somites crucial for the skull and vertebrae.
Intermediate mesoderm contributes to the urogenital system.
Lateral plate mesoderm forms the body cavity.
Initially, the lateral plate mesoderm is a solid sheet that splits into two layers; parietal and visceral.
The parietal layer, adjacent to the surface ectoderm, is continuous with the extraembryonic parietal layer.
The visceral layer is adjacent to the endoderm forming the gut tube.
Together, the parietal and visceral layers form the somatopleure and splanchnopleure, respectively.

Serous Membranes

Some parietal layer cells form the parietal layer of the serous membranes (peritoneal, pleural, pericardial).
Visceral layer cells form the visceral layer of the serous membranes.
Visceral and parietal layers connect as the dorsal mesentery, suspending the gut tube from the posterior body wall.
The dorsal mesentery extends continuously from the foregut to the hindgut.
The ventral mesentery connects the caudal foregut to the duodenum.
It results from the thinning of the mesoderm of the septum transversum, a structure important for liver and diaphragm formation.

Diaphragm and Thoracic Cavity

The septum transversum is a mesodermal plate between the thoracic and abdominal cavities.
It is initially continuous with the visceral mesoderm surrounding the heart.
As the lungs expand, the pericardioperitoneal canals become smaller.
Pleuropericardial folds grow, fusing with each other and forming the pleuroperitoneal membranes.
Mesodermal folds migrate to fuse, forming the pleuroperitoneal membranes and fully closing the thoracic cavity.
The pleuropericardial membranes create the fibrous pericardium in the adult.

Formation of the Diaphragm

The diaphragm forms from pleuroperitoneal membranes, the muscular components from cervical segments three to five, and the mesentery of the esophagus.
Phrenic nerves innervate the diaphragm, originating in the ventral primary rami of C3 to C5.
The cervical origin is due to early development of the diaphragm in the fourth week.
The diaphragm's descent and final location occur due to differential growth in the embryo.

Clinical Correlates: Ventral Body Wall Defects

Defects in the ventral body wall can lead to the protrusion of abdominal organs outside the body, such as hernias.

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Description

Explore the intricate development of the gut tube and body cavities in this embryology quiz. Understand the formation of the neural tube, mesoderm layers, and how these structures lead to the formation of the primitive body cavity. Test your knowledge on the key concepts of embryonic development.