2&4: Embryology

Question 0

What is the Vitilline tract?

Answer 0

A narrow tube that joins the yolk sac & the midgut

Generally obliterates during 7th week of fertilisation

Question 1

The external lining of the primitive gut tube is covered with splanchnic mesoderm. What will this develop into?

Answer 1

Smooth muscle of the viscera & blood vessels

Visceral peritoneum

Question 2

What is the result of the Vitilline tract persisting throughout development?

Answer 2

Meckels’ Diverticulum

Question 3

Foregut:
Where does it start?
Where does it terminate?
What is it’s blood supply?

Answer 3

Oesophagus

duodenum (proximal to bile duct)

Coeliac trunk

Question 4

Midgut:
Where does it start?
Where does it terminate?
What is it’s blood supply?

Answer 4

duodenum (distal to bile duct)

Proximal 2/3 transverse colon

Superior mesenteric artery

Question 5

Hindgut:
Where does it start?
Where does it terminate?
What is it’s blood supply?

Answer 5

Distal 1/3 transverse colon

Upper anal canal

Inferior mesenteric artery

Question 6

What are mesenteries?

Answer 6

Double layers of peritoneum which suspend the gut tube from the abdominal wall

Question 7

How does the developing foregut differ from the mid & hind gut in terms of mesenteries?

Answer 7

Foregut: both dorsal & ventral mesentery

Midgut & Hindgut: only dorsal mesentery

Question 8

What structure develops in the ventral mesentery of the foregut?

Answer 8

Liver

Question 9

In the 4th week of development, respiratory diverticulum develops in the ventral wall of the foregut.
What congenital problem can arise from abnormal development of the septum that divides these structures?

Answer 9

Tracheo-oesophageal fistula

Question 10

Which of the following does NOT result as a consequence of
rotation of the stomach?
A. Ventral border of the stomach rotates to lie to the right
B. Dorsal border of the stomach rotates to lie to the left
C. Dorsal mesogastrium forms the greater omentum
D. The loop of the duodenum rotates to the right
E. Ventral mesentery carried to the left

Answer 10

E

Question 11

The junction of the hindgut endoderm and the proctodeum 
ectoderm is indicated by: 
A. The pectinate line 
B. Levator ani  
C. External anal sphincter 
D. Anal columns 
E. The white line

Answer 11

A

Question 12

With respect to rotation of the midgut:
A. The midgut loop rotates clockwise
B. The jejunum returns to the abdominal cavity first and to the
right
C. The caecal bud returns to the abdominal cavity first and to the
right
D. The jejunum returns to the abdominal cavity first and to the
left
E. The caecal bud returns to the abdominal cavity first and to the
left

Answer 12

D

Question 13

True/False: The endoderm of the gut tube gives rise to: 
A. Kidney  
B. Liver  
C. Pancreas  
D. Lung  
E. Suprarenal gland

Answer 13

A. False
B. True
C. True
D. True
E. False

Question 14

True/False: With regard to congenital anomalies:
A. An omphalocoele occurs when the midgut loop fails to
undergo physiological herniation
B. Leakage of faeces through the umbilicus after birth results
from peristence of the allantois
C. Subhepatic caecum occurs due to failure of the caecal bud to
descend

Answer 14

A. False
B. False
C. True

Question 15

True/False: The dilated terminal part of the primitive gut tube: 
A. Is the allantois  
B. Is continuous with the allantois  
C. Is the cloaca  
D. Is divided by the urorectal septum  
E. Is the caecum

Answer 15

A. False
B. True
C. True
D. True
E. False

Question 16

Describe 2 mechanisms by which misplacement of the tracheo-oesophageal septum can lead to oesophageal atresia.

Name 2 additional potential causes for oesophageal atresia.

Answer 16

Septum can be posteriorly displaced:
spontaneously or
mechanical pressure on foregut dorsal wall, pressing it anteriorly

Recanalisation failure
Ischaemia secondary to vascular accident

Question 17

What sign may be observed in pre-natal assessment of a pregnancy where the foetus is affected by oesophageal atresia & why?

Answer 17

Accumulation of amniotic fluid (polyhydramnios) because foetus has upper GI obstruction, therefore normal swallowing of amniotic fluid not possible

Question 18

What is the location (attachments) of dorsal & ventral embryonic mesenteries?

Answer 18

Ventral: attached to foregut only
Dorsal: attached to foregut, midgut & hindgut

Question 19

Where does the liver develop?

Answer 19

In the ventral mesentery

Question 20

Where is the portal trial located along the primitive gut tube?

Answer 20

Between the foregut & midgut, along the free edge of the ventral mesentery

Question 21

Describe the normal development of the caecum

Answer 21

Appears as a conical caecal bud: a dilation of the caudal limb of the midgut (primary intestinal loop).
Develops as the primary intestinal loop returns to the abdomen after rotation.
First lies in the RUQ under the R lobe of liver.
Descends to RIF

Question 22

Describe & explain the history of pain described by a patient who has appendicitis

Answer 22

At first: periumbilical pain: appendix midgut derivative

Then: pain localises to RLQ as parietal peritoneum close to inflamed appendix becomes inflamed

Question 23

Which of the following would cause: large intestine on L, caecum & appendix suprapubic, small intestine on R:
A. non-rotation 
B. reversed rotation 
C. midgut volvulus 
D. omphalocoele 
E. gastroschisis 

What additional complication is this patient at risk of?

Answer 23

A

Volvulus leading to strangulation/ischaemia