3. Embroyolgy - Development Of The Peritoneal Cavity And Forgut

Question 1

What is the primitive gut tube lined with? What is it covered with?

Answer 1

Lined with endoderm.

Covered with splanchnic mesoderm.

Question 2

What do the foregut, midgut and hindgut begin as before embryonic folding completes?

Answer 2

Foregut and hindgut are blind diverticula.

Midgut is continuous with the yolk sac and so has an opening.

Question 3

What structures are derived from the foregut?

Answer 3

Oesophagus.
Stomach.
Pancreas, liver, gall bladder.
Duodenum proximal to sphincter of Oddi.

Question 4

What structures are derived from the midgut?

Answer 4

Duodenum distal to the sphincter of Oddi.
Jejunum.
Ileum.
Caecum.
Ascending colon.
Proximal 2/3 of transverse colon.

Question 5

What structures are derived from the hindgut?

Answer 5

Distal 1/3 transverse colon.
Descending colon.
Sigmoid colon.
Rectum.
Upper anal canal.
Internal lining of bladder and urethra.

Question 6

What 3 branches of the aorta does GI blood supply come from? What part does each go to, the foregut, midgut, or hindgut?

Answer 6

Celiac trunk - foregut.
Superior mesenteric artery - midgut.
Inferior mesenteric artery - hindgut.

Question 7

What structure in an exception of the rule in terms of GI blood supply? Why?

Answer 7

Pancreas.

Derived from foregut, but the head is supplied by both the celiac trunk and the superior mesenteric artery.

Question 8

What is the intraembryonic coelom?

Answer 8

A large cavity formed as the embryo folds.

Question 9

What is subdivided into the abdominal and thoracic cavities by the further diaphragm?

Answer 9

Intraembryonic coelom.

Question 10

What does the membrane lining the intraembryonic coelom specialise into as the cavity specialises?

Answer 10

Pericardium, pleural membrane, peritoneum, peritoneal cavity.

Question 11

What is the mesentry formed from?

Answer 11

A condensation of splanchnic mesoderm.

Question 12

What mesentery suspends the entire gut tube (foregut, midgut and hindgut) from the dorsal body wall?

Answer 12

Dorsal mesentery.

Question 13

What mesentery suspends just the foregut from the ventral wall?

Answer 13

Ventral mesentery.

Question 14

What divides the peritoneal cavity into the left and right sacs?

Answer 14

Dorsal and ventral mesenteries.

Question 15

What do the left and right sacs become?

Answer 15

Left sac - greater sac.

Right sac - lesser sac.

Question 16

What is the greater omentum formed from?

Answer 16

Dorsal mesentery.

Question 17

What is the lesser omentum formed from?

Answer 17

Ventral mesentery.

Question 18

What does the free edge of the lesser omentum conduct?

Answer 18

Portal triad - herpatic artery, portal vein, common bile duct.

Question 19

What influences the position of the greater and lesser sacs?

Answer 19

Rotation of the stomach around its long axis during development.

Question 20

What is a peritoneal reflection?

Answer 20

Any point there is a change in direction of the peritoneum eg from parietal peritoneum to mesentery.

Question 21

What are retroperitoneal structures?

Answer 21

Structures that are not suspended within the abdominal cavity. Were never in the cavity and never had a mesentery eg kidneys.

Question 22

What are secondarily retroperitoneal structures?

Answer 22

Structures that began development invested by peritoneum and had a mesentery, but with successive growth and development, the mesentery lost is lost through fusion at the posterior abdominal wall eg pancreas and duodenum.

Question 23

Where does the foregut extend from in an early embryo during folding?

Answer 23

Lung bud to liver bud.

Question 24

What forms in the 4th week of development, which leads to the separation of the developing GI and respiratory tracts?

Answer 24

A respiratory diverticulum forms in the ventral wall of the foregut, at the junction with the pharyngeal gut. This forms the respiratory primordium ventrally and the oesophagus forms dorsally, by the formation of the tracheoesophageal septum.

Question 25

What abnormalities can occur due to abnormal positioning of the tracheoesophageal septum?

Answer 25

Different combinations of a proximal blind-ending oesophagus and transoesophageal fistula.

Question 26

Development of what structures within the peritoneum leads to the development of the ventral mesentery?

Answer 26

Liver and biliary system

Question 27

What structure develops in the the dorsal and ventral mesentery?

Answer 27

Pancreas.

Question 28

What is the shape of the duodenum determined by?

Answer 28

Rotation of the stomach

Question 29

What is fusion fascia?

Answer 29

Fascia left at the point where the mesentery is lost in secondarily retroperitoneal structures.