Embryology of the foregut

Question 1

where does the primitive gut tube extend to

Answer 1

fro the orophrngeal membrane to the cloacal membrane

Question 2

what is the mid gut continuous with

Answer 2

the yolk sac at the vitelline duct

Question 3

what is the epithelial lining derived from

Answer 3

endoderm

Question 4

what is smooth muscle and connective tissue derived from

Answer 4

surrounding visceral mesoderm

Question 5

what is the primitive gut suspended by

Answer 5

by the dorsal mesentery from the posterior abdominal wall

Question 6

what are the borders of the dorsal mesentery

Answer 6

from lower oesophagus to cloaca

Question 7

what ate the borders of the ventral mesentery

Answer 7

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

Question 8

what do villitine arteries give rise to

Answer 8

arteries of the GIT

Question 9

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

Answer 9

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

Question 10

what are the 3 types fo abnormal recanalistaion

Answer 10

duplication

incomplete canalisation - stenosis or blockage (atresia)

Question 11

which part of the GIt is most common to abnormal recanalisation

Answer 11

ileum then duodenum

Question 12

what are duplication cysts

Answer 12

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

Question 13

how does the foregut initially develop

Answer 13

gives rise to respiratory diverticulum

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

Question 14

what does displacement of the tracheosophegeal spetum do

Answer 14

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

Question 15

what does the oesophagus derive from and in what week

Answer 15

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

Question 16

what is congenital hiatal hernia

Answer 16

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

Question 17

when does the stomach first appear

Answer 17

4th week with dilation of the foregut

Question 18

what does differential growth in week 5 form

Answer 18

the greater curvature of the stomach

Question 19

what happens to the stomach in week 7-8

Answer 19

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

Question 20

what happens to the vagus nerves during stomach rotation

Answer 20

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

Question 21

what is the second rotation of the stomach

Answer 21

ventrodorsal
grater curvature faces slightly caudally
lesser curvature slightly cranially

Question 22

describe the formation of the lesser peritoneal sac

Answer 22

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

Question 23

what is the greater sac

Answer 23

the remaining peritoneal cavity not behind the stomach after rotation

Question 24

what is the epiploic foramen

Answer 24

of winslow

narrowing opening that connects the greater and lesser sacs

Question 25

how does formation of the greater omentum occur

Answer 25

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

Question 26

what does the mesentery of the transverse colon fuse with

Answer 26

the posterior layer of the greater momentum

Question 27

what is congenital pyloric stenosis

Answer 27

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

Question 28

what are the signs of congenital pyloric stenosis

Answer 28

palpable pyloric mass
projectile vomiting
visible peristalsis

Question 29

what is heterotopic gastric tissue

Answer 29

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

Question 30

describe the formation of the duodenum

Answer 30

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

Question 31

what are the two origins of the duodenum

Answer 31

proximal first half is foregut, distal half is midgut