2&4: Embryology Flashcards
What is the Vitilline tract?
A narrow tube that joins the yolk sac & the midgut
Generally obliterates during 7th week of fertilisation
The external lining of the primitive gut tube is covered with splanchnic mesoderm. What will this develop into?
Smooth muscle of the viscera & blood vessels
Visceral peritoneum
What is the result of the Vitilline tract persisting throughout development?
Meckels’ Diverticulum
Foregut:
Where does it start?
Where does it terminate?
What is it’s blood supply?
Oesophagus
duodenum (proximal to bile duct)
Coeliac trunk
Midgut:
Where does it start?
Where does it terminate?
What is it’s blood supply?
duodenum (distal to bile duct)
Proximal 2/3 transverse colon
Superior mesenteric artery
Hindgut:
Where does it start?
Where does it terminate?
What is it’s blood supply?
Distal 1/3 transverse colon
Upper anal canal
Inferior mesenteric artery
What are mesenteries?
Double layers of peritoneum which suspend the gut tube from the abdominal wall
How does the developing foregut differ from the mid & hind gut in terms of mesenteries?
Foregut: both dorsal & ventral mesentery
Midgut & Hindgut: only dorsal mesentery
What structure develops in the ventral mesentery of the foregut?
Liver
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?
Tracheo-oesophageal fistula
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
E
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
A
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
D
True/False: The endoderm of the gut tube gives rise to: A. Kidney B. Liver C. Pancreas D. Lung E. Suprarenal gland
A. False B. True C. True D. True E. False
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
A. False
B. False
C. True
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
A. False B. True C. True D. True E. False
Describe 2 mechanisms by which misplacement of the tracheo-oesophageal septum can lead to oesophageal atresia.
Name 2 additional potential causes for oesophageal atresia.
Septum can be posteriorly displaced:
spontaneously or
mechanical pressure on foregut dorsal wall, pressing it anteriorly
Recanalisation failure
Ischaemia secondary to vascular accident
What sign may be observed in pre-natal assessment of a pregnancy where the foetus is affected by oesophageal atresia & why?
Accumulation of amniotic fluid (polyhydramnios) because foetus has upper GI obstruction, therefore normal swallowing of amniotic fluid not possible
What is the location (attachments) of dorsal & ventral embryonic mesenteries?
Ventral: attached to foregut only
Dorsal: attached to foregut, midgut & hindgut
Where does the liver develop?
In the ventral mesentery
Where is the portal trial located along the primitive gut tube?
Between the foregut & midgut, along the free edge of the ventral mesentery
Describe the normal development of the caecum
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
Describe & explain the history of pain described by a patient who has appendicitis
At first: periumbilical pain: appendix midgut derivative
Then: pain localises to RLQ as parietal peritoneum close to inflamed appendix becomes inflamed
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?
A
Volvulus leading to strangulation/ischaemia
