Gi

Question 0

During which weeks is the primitive gut tube formed?

Answer 0

The primitive gut tube is formed during Week 3 and 4.

Question 1

At what week does the liver form? Where from?

Answer 1

Liver forms at WEEK 3 from a ventral outgrowth of foregut as an out pocketing of the future duodenum. Hepatic diverticulum

Question 2

How is the primitive gut tube formed?

Answer 2

It is formed via craniocaudal and lateral folding of the embryo.

Question 3

The visceral and parietal mesoderm give rise to what?

Answer 3

Gives rise to visceral and parietal peritoneum.

Question 4

How is the primitive gut tube suspended?

Answer 4

Suspended from the anterior abdominal wall by dorsal mesentery.

Question 5

What dies the ventral mesentery form?

Answer 5

Forms lesser omentum and falciform ligament.

Question 6

What do the vitelline arteries give rise to?

Answer 6

Th give rise to the branches of the GI tract

Question 7

At what week does the stomach become first apparent?

Answer 7

Stomach becomes apparent at WEEK 4 as fusiform dilatation of the foregut.

Question 8

During which weeks does the oesphagus lengthen?

Answer 8

Oesophagus lengthens during Weeks 4-7

Question 9

If the endoderm doesn’t proliferate fast enough what can happen?

Answer 9

Oesophageal atresia can occur which prevents the fetus from swallowing amniotic fluid, returning it to the mother (polyhydramnios)

Question 10

During week 5 what happens to the midgut?

Answer 10

The midgut rapidly expands to form the primary intestinal loop and the liver grows.

Question 11

At what week does the pancreas and spleen develop/ form?

Answer 11

The pancreas forms at week 5. The spleen also develops during week 5.

Question 12

During weeks 7-8 what happens to the stomach?

Answer 12

Rotates around 2 axes. 90 degree rotation around craniocaudal axis causes lesser curvature to move from ventral to right.

Greater curvature moves from dorsal to left.

Also slight ventral dorsal movement so greater curvature faces slightly caudally

Question 13

As the stomach rotates what is formed?

Answer 13

A space is left behind it which forms the lesser peritoneal sac.

Question 14

The primary intestinal loop has two limbs, what are they?

Answer 14

Cranial and caudal limbs.

Cranial forms distal duodenum, jejunum, and proximal ileum.

Caudal: distal ileum, caecum, appendix, ascending and proximal 2/3 of transverse colon.

Question 15

How and when does the midgut become herniated?

Answer 15

Week 6 due to rapid growth of the liver

Question 16

During week 6 how does the midgut rotate?

Answer 16

The midgut rotates 90 degrees anti clockwise around the SMA as hernination occurs.

Brings cranial limb right and caudal limb left.

Question 17

When does the small ventral pancreatic bud and larger dorsal pancreatic bud fuse?

Answer 17

During week 6.

Question 18

What does the dorsal bud of pancreas give rise to?

Answer 18

Head, body and tail. Ventral forms uncinate.

Question 19

When does the midgut return to the abdomen after herniation?

Answer 19

In week 10. The midgut returns and rotates a further 180 degrees anticlockwise.

Brings proximal jejunal loops to left and caecum lies inferior to liver.

Question 20

During which week does bile production begin?

Answer 20

Week 12.

Question 21

During which week do gastric cells differentiate?

Answer 21

Week 9.

Question 22

During which week is the veniform appendix formed?

Answer 22

Week 10 as the midgut rotates 180 degrees anti clockwise. Caecum develops a wormlike diverticulum.

Question 23

Which week does the midgut finally completely return to the abdomen?

Answer 23

Week 11 after a 270 degree total rotation anticlockwise.

Question 24

After the midgut has returned, what happens to the caecum?

Answer 24

Caecum descends from below the liver to right iliac fossa.

This pulls the ascending and transverse colon into place.

Question 25

During weeks 4-6 a layer of mesoderm extends caudally. How does this contribute to the formation of the hind gut?

Answer 25

As it extends caudally, it separates the urogenital sinus and anorectal canal to form the urorectal septum.

Question 26

What will the ventral part of cloaca (urogenital sinus) form?

Answer 26

Urogenital sinus will form the bladder, pelvic urethra, penile urethra and caudal part of vagina.

Question 27

When does the cloacal membrane rupture and what does it create?

Answer 27

In week 7 it ruptures to create the anal opening and a ventral opening for the urgent tail sinus.

Question 28

What does the tip of the urorectal septum form?

Answer 28

The urorectal septum lies between anal opening and opening for urogenital sinus to form perineal body.

Question 29

What is the anal canal formed from?

Answer 29

Upper 2/3 - from hindgut. Endoderm

Lower 1/3 - proctodeum (anal pit)

Question 30

Formation of gut lumen. When does the gut tube become occluded?

Answer 30

Week 6 as endoderm derived epithelial lining proliferates.

Apoptosis from week 6-8 create vacuoles.

Question 31

When do the vacuoles in the gut lumen recanalise the gut tube?

Answer 31

By week 9