GI Embryology

Question 1

What is the cloaca and describe it’s function

Answer 1

It is the enlarged terminal part of the hindgut, lined with endoderm

Question 2

Foregut includes?

Answer 2

Pharynx
LRT
Oesophagous 
Stomach
First part of duo above pancreatic duct 
Hepatic and biliary apparatus and pancreas

Question 3

Midgut?

Answer 3

Distal 2/3 of duo
Jejunem 
Ileum
Caecum
Appendix
Asc colon
Proximal 2/3 trans colon

Question 4

Hindgut?

Answer 4

Distal 1/3 of trans colon
Desc colon
Sigmoid colon
Rectum 
Upper part of anal canal

Question 5

What is most of the primordial gut derived from?

Answer 5

Endoderm

Question 6

What are the cranial and caudal ends both derived from?

Answer 6

Ectoderm forms the epithelial lining of both

Question 7

What is the intraembryonic coloem?

Answer 7

The cavity whicg gives rise to thoracic and abdominal cavities, also separates the mesoderm into 2 layers

Question 8

What is oesophageal atresia and a tracheoesophageal fistula?

Answer 8

Fistula is caused by abnormal deviation of tracheoesophageal septum
Atresia is the failure of recananlisation
Also polyhyramnois caused by atresia is too much amniotic fluid

Question 9

Stomach development

Answer 9

90 degrees longitudinal axis
180 degrees transverse axis
Dorsal mesentry becomes greater curvature
270 rotation in total
Omental bursa sit behind stomach as a result of rotation

Question 10

Development of the pancreas

Answer 10

Dorsal and ventral buds are formed
the ventral bud rotates around posteriorly to join the dorsal bud
the ventral bud forms the head of the pancreas where as the dorsal blood forms the tail

Question 11

Pancreas patho

Answer 11

Of failure of ventral bud to rotate leads to an annular pancreas which may lead to duodenal stenosis

Question 12

what is the spleen derived from?

Answer 12

mesenchyme (mesoderm)

Question 13

formation of midgut loop?

Answer 13

physiological umbilical herniation, rotation of 90 degrees in umbilicus, retraction of intestinal loops and then further rotation counterclockwise 180degrees

Question 14

midgut patho?

Answer 14

failure of retraction leads to omphalocele (covered in amnion or peritoneum) or gastroschisis, same thing however not covered in amnion or peritoneum
also there may be a vitilline duct remnant, it may be a fistula, cyst or ligament

Question 15

what is the allantois?

Answer 15

It later becomes the urachus which functions as the embryonic bladder, getting rid of nitrogenous waste as it joins with the yolk sac 🥚

Question 16

what does the cloacal membrane do?

anus formation?

Answer 16

separates the cloaca and anal pit (ectoderm)
week 7 ectoderm proliferates and closes up caudal end
week 9 it reopens, if not an imperforate anus can be formed

Question 17

hindgut patho

Answer 17

urorectal fistula, rectovaginal fistula, rectoanal atresia and imperforate anus