Development of the GI tract

Question 1

Describe the primitive embyro

Answer 1

Figure of 8, upper inner circle lined by ectoderm
lower inner circle lined by endoderm
Outside layer mesoderm

Question 2

What does the embryonic ectoderm give rise to?

Answer 2

Brain, spinal cord etc.

Question 3

What does the embryonic mesoderm give rise to?

Answer 3

CT, bone, blood, cartilage

Question 4

What does the embryonic endoderm give rise to?

Answer 4

Viscera

Question 5

What is the blood supply of each section of the gut?

Answer 5

Foregut = Aorta, coeliac trunk
Midgut = superior mesenteric artery
Hindgut = inferior mesenteric artery

Question 6

What does the foregut give rise to?

Answer 6

Pharynx + oesophagus
Lower resp. tract
Stomach
Duodenum (proximal to opening of bile duct)
Liver + pancreas
Biliary apparatus

Question 7

How does the lower respiratory tract form in embryo?

Answer 7

Respiratory diverticulum forms off of oesophagus,
splits into two parts at the bottom like an upside-down ‘Y’ as tracheo-oesophageal septum forms.
Lung buds form as trachea separates from oesophageal tube at pharynx

Question 8

What is oesophageal atresia?

Answer 8

Gap in oesophagus, not continuous.

Lower part of oesophagus attached to lung bud at the side

Question 9

What is an oesophageal fistula?

Answer 9

Part of trachea attached to oesophagus (like a bridge)

Question 10

What is oesophageal atresia and fistula

Answer 10

Part of trachea attached to oesophagus (like a bridge) then below the bridge, oesophagus not continuous.
Rest of oesophagus attached to lung bud off of trachea

Question 11

How does the pancreas develop?

Answer 11

At start, there is a dorsal (larger) and a ventral pancreas, the ventral pancreas swings around and joins with dorsal pancreas; pancreatic duct travels through ventral then dorsal pancreas then joins into the duodenum.

Question 12

What does the midgut give rise to?

Answer 12

Duodenum, distal opening of bile duct
Jujenum
Ileum
Caecum + appendix
Ascending colon
proximal 2/3rds of transverse colon

Question 13

What twists are meant to happen in the formation of the midgut?

Answer 13

The small intestine and the large intestine should rotate around each other; firstly a 90 degree anticlockwise, then a 180 degree anticlockwise

Question 14

Omphalocoele

Answer 14

Midgut born outside body within umbilical cord

Question 15

Gastroschisis

Answer 15

Midgut born just laterally to umbillicus through abdominal wall

Question 16

What does the hindgut give rise to?

Answer 16

distal 1/3 of transverse colon
descending colon
sigmoid colon
rectum
superior part of anal canal
Epithelium of the urinary bladder + most of urethra

Question 17

Describe the cloaca

Answer 17

Rectum closed off - urorectal canal not continuous - no need.
Separated by urorectal septum

Question 18

Describe the mesenteries present in different parts of the gut in embryo

Answer 18

Fore gut = dorsal and ventral mesentaries

hind and mid gut = only dorsal

Question 19

What is volvulus

Answer 19

Abnormal twisting of small intestine