Embryology of the foregut Flashcards

1
Q

where does the primitive gut tube extend to

A

fro the orophrngeal membrane to the cloacal membrane

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2
Q

what is the mid gut continuous with

A

the yolk sac at the vitelline duct

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3
Q

what is the epithelial lining derived from

A

endoderm

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4
Q

what is smooth muscle and connective tissue derived from

A

surrounding visceral mesoderm

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5
Q

what is the primitive gut suspended by

A

by the dorsal mesentery from the posterior abdominal wall

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6
Q

what are the borders of the dorsal mesentery

A

from lower oesophagus to cloaca

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7
Q

what ate the borders of the ventral mesentery

A

from lower oesophagus to 1st part of duodenum which forms the lesser momentum and falciform ligament

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8
Q

what do villitine arteries give rise to

A

arteries of the GIT

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9
Q

when does formation of the definitive gut lumen occur and what happens

A

week 6 - proliferation of the endoderm derived from epithelial lining occludes gut tube
apoptosis of epithelium over next 2 week creates vacuoles - recanalisation
vacuoles coalesce to fully recanalise in gut tube by week 9

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10
Q

what are the 3 types fo abnormal recanalistaion

A

duplication

incomplete canalisation - stenosis or blockage (atresia)

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11
Q

which part of the GIt is most common to abnormal recanalisation

A

ileum then duodenum

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12
Q

what are duplication cysts

A

rare but have high incidence of complications eg bowel obstruction or intussusception

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13
Q

how does the foregut initially develop

A

gives rise to respiratory diverticulum

separates from RD by forming a tracheosophageal septum - pharynx and oesophagus

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14
Q

what does displacement of the tracheosophegeal spetum do

A

oesophageal atresia - prevents foetus swelling amniotic fluid and retiring it to the mother through placental circulation
this is polyhydraminos

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15
Q

what does the oesophagus derive from and in what week

A

week 4 caudal to the lung bud
epithelial lining from endoderm
smooth muscle from mesoderm
skeletal muscles from paraxial mesoderm

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16
Q

what is congenital hiatal hernia

A

insufficient elongation of oesophagus during week 4-8 which means stomach is supradiaphragmatic

17
Q

when does the stomach first appear

A

4th week with dilation of the foregut

18
Q

what does differential growth in week 5 form

A

the greater curvature of the stomach

19
Q

what happens to the stomach in week 7-8

A

90 degree clockwise rotation around the craniocaudial axis which moves the lesser curvature into the ventral position

20
Q

what happens to the vagus nerves during stomach rotation

A

initially found on left and right side fo the gut tube but rotated so left vagus trunk is anterior and right becomes dorsal

21
Q

what is the second rotation of the stomach

A

ventrodorsal
grater curvature faces slightly caudally
lesser curvature slightly cranially

22
Q

describe the formation of the lesser peritoneal sac

A

as stomach rotates it creates a space behind it the lesser peritoneal sac (omental bursa)

23
Q

what is the greater sac

A

the remaining peritoneal cavity not behind the stomach after rotation

24
Q

what is the epiploic foramen

A

of winslow

narrowing opening that connects the greater and lesser sacs

25
Q

how does formation of the greater omentum occur

A

dorsal mesentery attached to the greater curvature of the stomach and the posterior abdominal wall continues to grow
creates space between in called omental bursa
ventral and dorsal folds fuse before birth

26
Q

what does the mesentery of the transverse colon fuse with

A

the posterior layer of the greater momentum

27
Q

what is congenital pyloric stenosis

A

narrowing of pyloric sphincter caused by hypertrophy of smooth muscle
1 in 500 births
more common in males 5:1
restricts gastric emptying which leads to dilation of the stomach

28
Q

what are the signs of congenital pyloric stenosis

A

palpable pyloric mass
projectile vomiting
visible peristalsis

29
Q

what is heterotopic gastric tissue

A

abnormal epithelial differentiation which leads to ectopic gastric tissue
inflammation and ulceration in area which can rupture gut wall

30
Q

describe the formation of the duodenum

A

elongates in week 4 resulting in ventral C shape
dragged to the right but stomach rotation
dorsal mesentery attached to the duodenum degenerates so that the duodenum lies against the posterior abdominal wall - secondarily retroperitoneal

31
Q

what are the two origins of the duodenum

A

proximal first half is foregut, distal half is midgut