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Question 1

When does the embryo begin to fold?

Answer 1

4th week

Question 2

What direction does the embryo fold?

Answer 2

Lateral and craniocaudal

Question 3

What is created by lateral folding of the embryo?

Answer 3

Ventral Body wall and tubular primitive gut tube

Question 4

What is created by craniocaudel folding of the embryo?

Answer 4

Creates cranio and caudel pockets from yolk sac endoderm (beginning primitive gut development)

Question 5

What is the Primitive Gut Tube lined by?

Answer 5

Endoderm

Question 6

What can the Primitive Gut Tube be divided into?

Answer 6

Foregut, Midgut and Hindgut

Question 7

Describe the formation of the PGT

Answer 7

Pinches off from yolk sac cavity in 3rd week.
Runs from stomatodeum to proctodeum
Opening at the umbilicus = Vitelline Duct

Question 8

What is the external lining of the PGT?

Answer 8

Splanchnic mesoderm

Question 9

How and where is the PGT suspended?

Answer 9

Intraembryonic Coelom by double layer of splanchnic mesoderm

Question 10

Describe the midgut innervation

Answer 10

Parasympathetic: Vagus Nerve
Sympathetic: Superior Mesenteric Ganglion & Plexus

Question 11

Describe the hindgut innervation

Answer 11

Parasympathetic: Pelvic Nerve (S2,3,4)
Sympathetic: Inferior Mesenteric Ganglion & Plexus

Question 12

What is the mesoderm surrounding the gut slit into?

Answer 12

Layers

Question 13

What are the the layers surrounding the gut split into? What do they develop into?

Answer 13

Somatic: Develops into muscles and fasciae of abdominal wall
Splanchnic: Develops into smooth muscles of gut wall

Question 14

What is the space that is created by the split called?

Answer 14

Coelamic Cavity (forerunner of the pleural and partitioner cavity, primitive gut is therefore surrounded by Coelomic Cavity)

Question 15

What happens as Lateral Folding progresses?

Answer 15

Two sides of abdominal wall meet and form the lineal alba

Question 16

What do the muscles and fascia of the abdominal wall develop from?

Answer 16

Somatic Mesoderm

Question 17

Describe the formation of the Coelomic Cavity and its future

Answer 17

The mesoderm surrounding the gut splits into the somatic and splanchnic and the space between them forms the Coelomic Cavity. Will eventually be divided by the diaphragm

Question 18

Where is the developing gut attached to? How?

Answer 18

Roof of the abdominal cavity by a fold of mesoderm known as the dorsal mesoderm

Question 19

What attaches the foregut and where?

Answer 19

Ventral Mesentary and to the floor

Question 20

Describe the formation of the right and left spaces and what they will go on to contribute towards

Answer 20

Dorsal mesentary in the region of the foregut creates the right and left spaces
Left space will contribute towards the greater peritoneal sac
Right space will contribute towards the less peritoneal sac

Question 21

Where is the greater and lesser omentum formed?

Answer 21

Greater formed from the dorsal mesentary of the stomach
Lesser formed from the ventral mesentary of the stomach
Formed by stomach rotation

Question 22

Describe the rotation of the stomach

Answer 22

Stomach widest part of the foregut and starts symmetrically. However, it begins to expand towards the left and this faster growth of the dorsal border creates the greater curvature

Question 23

What axis does the stomach rotate around?

Answer 23

Longitudinal and anteroposterior

Question 24

What are the results of the stomach rotation?

Answer 24

Right becomes anterior and left becomes posterior
Vagus nerves lie anterior/posterior instead of left/right
Shifts the cardia and the pylorus from the midline, pushing greater curve inferiorly
Moves the lesser sac behind the stomach
Creates the greater omentum

Question 25

Describe some secondary retro peritoneal structures

Answer 25

Ascending and descending colon | Duodenum

Question 26

Describe how the duodenum is secondary retro peritoneal

Answer 26

Mesentary pushed against the posterior abdominal wall due to rotation and liver size. It then gets grown over which forms an avascular fusion fascia

Question 27

Describe the formation of the Respiratory Primordium

Answer 27

Respiratory Diverticulum forms in the ventral wall of the foregut at the junction with the pharyngeal gut This becomes the respiratory primordium ventrally and the oesophagus dorsally Divided by the tracheosophageal septum

Question 28

Describe some foregut derived glands formed in the ventral mesentary

Answer 28

Liver Biliary System Greater head of the pancreas

Question 29

Describe the foregut derived gland formed in the forsal mesentary

Answer 29

The rest of the pancreas

Question 30

Where does the liver develop?

Answer 30

From hepatic bud within ventral mesentary

Question 31

Describe what happens to the duodeum in the 5th and 6th weeks

Answer 31

Loses its lumen due to fast growing lining | Recanalised later on