Development

Question 1

Foregut area

Answer 1

Anything in the digestive tract before the middle of the duodenum

Question 2

Midgut area

Answer 2

Distal 1/2 of duodenum to last 1/3 of transverse colon

Question 3

Hindgut area

Answer 3

Distal 1/3 of transverse colon to last 1/3 of anal canal

Question 4

Lateral folding of the embryo

Answer 4

2D structure of 3 layers (ectoderm, mesoderm and endoderm) forms a cylinder
The ectoderm and mesoderm fold laterally and ventrally which closes off the endoderm forming a separated gut tube structure
The endoderm forms the epithelial lining of the tube
The mesoderm gives rise to the supporting structures and smooth muscle
The outer mesenchymal ayer gives rise to the outer tissue layer
The space in between the mesoderm is the body cavity

Question 5

Longitudinal folding

Answer 5

3D structure bends over to form the foetal position
At about 17 days the opening of the gut tube closes like a purse string, dividing into foregut and hindgut. The midgut remains open to the yolk sac
Further folding causes communication with yolk sac to get smaller and the 3 gut regions become more refined

Question 6

2 membranes closing off the tube

Answer 6

Oropharyngeal membrane at the cranial end

Anal membrane at the caudal end

Question 7

Key embryonic event at week 4

Answer 7

Oropharyngeal membrane ruptures

Question 8

Key embryonic event at week 8

Answer 8

Anal membrane ruptures

Question 9

Lumen of the gut tube

Answer 9

Initially the gut tube is patent. As epithelium proliferates the lumen of the gut tube is plugged up. During week 8, recanalisation occurs

Question 10

The foregut receives blood from:

Answer 10

The coeliac trunk

Question 11

The midgut receives blood from:

Answer 11

The superior mesenteric artery

Question 12

The hindgut receives blood from:

Answer 12

The inferior mesenteric artery

Question 13

Tracheoesophageal fistula/atresia

Answer 13

Fistula: connection
Atresia: blockage
Both occur as a result of incomplete partitioning

Question 14

Congenital hiatal hernia

Answer 14

Short oesophagus

Displaces stomach cranially and herniates into thorax through oesophageal hiatus

Question 15

Dilation and rotation of stomach

Answer 15

Gut tube starts to dilate and continues through the rotations
Rotation of tube on long axis 90° clockwise. Anterior mesogastrium moves to the right and posterior mesogastrium moves to the left.
Then, rotation of tube on coronal axis 90° clockwise. Right boundary becomes superior (lesser curvature) and left boundary becomes inferior (greater curvature)

Question 16

Formation of greater omentum

Answer 16

As dorsal mesogastrium is dragged round by rotation of stomach it hangs down under the weight of gravity. Both sides of the hanging fold fuse together making a 4 layered peritoneal structure, the greater omentum.

Question 17

Congenital hypertrophic pyloric stenosis

Answer 17

Marked thickening of the muscular wall of the pylorus, blocking exit of the stomach into the duodenum

Question 18

Hepatic diverticulum

Answer 18

Outgrowth of the duodenum at week 4 of development forming the liver and biliary apparatus

Question 19

Pancreas development

Answer 19

Develops between both layers of mesogastrium

Ventral and dorsal bud: eventually anastamose forming a pancreatic duct

Question 20

Midgut herniation

Answer 20

Normal process where loop migrates through into umbilical cord. Eventually this herniation retracts and the loop returns to the abdominal cavity

Question 21

Abnormal midgut rotations

Answer 21

Non-rotation
Twisting
Reversed rotation
Sub-hepatic caecum and appendix (failure to descend)
Internal hernia
Midgut volvulus (obstructs duodenum)

Question 22

Umbilical herniation or fistula

Answer 22

Failure of umbilical cord to close properly. Gut herniates through weak region in the body wall

Question 23

Meckels diverticulum

Answer 23

Ileal diverticulum

Remnant of the vitelline duct

Question 24

Cloaca

Answer 24

Expanded distal part of hindgut divided into dorsal and ventral parts

Question 25

Mesenchymal urorectal septum

Answer 25

As septum grows it separates rectum from urogenital sinus

Question 26

Rectum/anal canal

Answer 26

Boundary between outer ectoderm and inner endoderm

Inferior mesenteric artery supplies upper 2/3

Question 27

Anocutaneous line

Answer 27

Portion of the anal canal where the lymphatics change. Below this line superficial inguinal nodes are found

Question 28

Hirschsprungs disease

Answer 28

Segment of colon is dilated due to absence of ANS ganglion cells in distal gut wall
Peristalsis failure in aganglionic part means the colon can’t relax which prevents movement of intestinal contents

Question 29

Imperforated anus

Answer 29

Failure of anal membrane to perforate

Question 30

Rectal atresia

Answer 30

Anal canal and rectum are separated

Fistulas may present which can connect intestine to urethra, bladder or vagina