Development of the Peritoneal Cavity and the Foregut

Question 1

How do we get an anterior body wall?

Answer 1

Folding of the embryo

Lateral folding = creates ventral body wall

Question 2

What does folding in the 4th week of the embryo achieve?

Answer 2

Laterally = ventral body wall, primitive gut becomes tubular

Craniocaudally = cranial + caudal pockets from yolk sac endoderm

Question 3

What is the primative gut?

Answer 3

Lined by endoderm – devel into the lining and glands

Runs from stomatodeum (future mouth) rostrally to proctodeum (future anus) caudally

Blind pouches at the head and tail end

Opening at umbilicus

Splanchnic mesoderm covering

Question 4

How does the primitive gut form?

Answer 4

Craniocaudally folding = cranial + caudal pockets from yolk sac endoderm (begining of primative gut tube formation

Lateral folding = primative gut becomes tubular

Question 5

What is somatic mesoderm vs splanchnic mesoderm?

Answer 5

Somatic = relating to the body, lining body wall

Splanchnic = relating to the viscera

Question 6

What are the 3 divisions of the primitive gut tube?

Answer 6

Foregut

Midgut

Hindgut

Question 7

What does the embryonic foregut turn into?

Answer 7

Oesophagus

Stomach

Pancreas, liver, gall bladder

Duodenum (proximal to bile duct entrance)

Question 8

What does the embryonic midgut turn into?

Answer 8

Duodenum (distal to bile duct entrance)

Jejunum

Ileum

Cecum

Ascending colon

Proximal 2/3 transverse colon

Question 9

What does the embryonic hindgut turn into?

Answer 9

Distal 1/3 transverse colon

Descending colon

Sigmoid colon

Rectum

Upper anal canal

Internal lining of bladder, urethra

Question 10

How is the primitive gut tube related to the blood supply of the GI tract?

Answer 10

Each section of the primitive gut tube receives a distinct branch from the abdo aorta

Foregut = celiac trunk

Midgut = superior mesenteric artery

Hindgut = inferior mesenteric artery

Structures close to junctions receives a mixed blood supply

Question 11

What is the intraembryonic coelom?

Answer 11

Cavity, divided by diaphragm that will give rise to the thoracic and abdo cavities

Formed as the embryo folds

Begins as one large cavity from top to bottom of the embryo

Question 12

Define mesentery

Answer 12

Double layer of peritoneum suspending the gut tube from the abdo wall

Allows conduit or blood and nerve supply

Allows mobility where needed

Question 13

How does the mesentery form?

Answer 13

Primitive gut tube drops down into the intraembryonic coelom

Splanchnic mesoderm is dragged down = forms mesentery

Question 14

Where is mesentery found?

Answer 14

Dorsal mesentery = suspends entire gut tube from dorsal body wall

Ventral mesentery = only in the region of the foregut

Question 15

What is the greater sac of the abdo?

Answer 15

Sac inside the abdo but outside the lesser sac

Question 16

What is the lesser sac of the abdo?

Answer 16

Through the epiploic foramen, behind the stomach

Question 17

What is the omenta?

Answer 17

Specialised regions of peritoneum

Question 18

What is the greater omentum?

Answer 18

Formed from the dorsal mesentery

Hangs down from the stomach, doubles back to the transverse colon before reaching the posterior abdo wall

First structure seen in abdo cavity

Question 19

What is the lesser omentum?

Answer 19

Formed from ventral mesentery

Runs from stomach to liver, free edge conducts portal triad

Smaller, short

Question 20

What influences the position of the great and lesser omentum?

Answer 20

Rotation of the stomach around the long axis during devel

Question 21

What is secondary retroperitoneal?

Answer 21

Began devel invested by peritoneum, has a mesentery but with devel the mesentery is lost through fusion at posterior abdo wall, due to massive expansion of the GI tract

Question 22

What separates the devel GI and resp tracts?

Answer 22

Tracheoesophageal septum

Question 23

What structures have mesenteries?

Answer 23

Jejunum

Ileum

Stomach

Uterus

Transverse colon

Question 24

What structures are retroperitoneal?

Answer 24

Pancreas

Kidneys

aorta

Question 25

What structures are secondary retroperitoneal?

Answer 25

Pancreas

Duodenum

Descending colon

Question 26

What is fusion fascia?

Answer 26

The point at which the mesentery is lost and fuses with the membrane