Development of the GI tract part 2

Question 1

What does the midgut give rise to?

Answer 1

Small intestine (most of duodenum)

Caecum and appendix

ascending colon

2/3 of transerse colon

Question 2

What is the primary intestinal loop?

Answer 2

Midgut elongates enormously and runs out of space

makes a loop thats connected to the yolk sac by the vitelline duct and has cranial and caudal limbs, sma as axis

Question 3

When is physiological herniation?

Answer 3

6th week

Question 4

What happens in physiological herniation?

Answer 4

primary intestinal loop growth is rapid

liver grows rapidly

abdominal cavity is too small to acommodate both

intestines hernate into umbilical cord

Question 5

What are the steps of midgut rotation?

Answer 5

Question 6

What happens after rotation?

Answer 6

descent of caecal bud

Question 7

What happens if there is incomplete rotation of the midgut?

Answer 7

makes only 1 90 degree rotation- left sided colon

makes on 90 degree rotation clockwise- transverse colon passes posterior to the duodenum

Question 8

What are the risks associated with midgut defects?

Answer 8

Strangualtion and ischaemia

Question 9

What is herniation?

Answer 9

Protrusion of a viscus through a hole

Question 10

What happens to remnants of the yolk sac?

Answer 10

vitelline duct persists resulting in vitelline cyst, vitelline fistula and meckels divericulum

Question 11

What is meckels diveriticulum?

Answer 11

Question 12

Where does recanalisation occur?

Answer 12

oesphagus, bile duct, small intesting

Question 13

Why does recanalisation occur?

Answer 13

Cell grwoth becomes so rapid that the lumen is completely obliterated

Question 14

What happens if recanalisation is unsuccessful?

Answer 14

Atresia- lumen obliterated or stenosis- lumen narrowed

mainly in duodenum

Question 15

What is a pyleric stenosis?

Answer 15

Hypertrophy of the circular muscle in the region of the pyloric sphincter

-not a reacanalisation failure

causes projectile vomiting

Question 16

What is gastroschisis?

Answer 16

Failure of closure of the abdominal wall during folding of the embryo

Leaves gut tube and derivatives outside the body cavity

Question 17

What is omphalocoele (exophalos)

Answer 17

Persistance of the physiological herniation

Differs from umbilical hernia because hernia has skin and subcutaneous tissue

Question 18

What does the hindgut give rise to?

Answer 18

Distal 1/3 transverse colon

Descending colon

rectum

superior part of anal canal

epithelium of urinary bladder

Question 19

How is the anal canal divided?

Answer 19

Pectinate line into histologically superior and inferior parts

Question 20

What is the proctodeum?

Answer 20

Junction between two embryonic germ layers

Question 21

What is above and below the pectinate line?

Answer 21

Question 22

What does the contribution of two embryonic tissues to the anal canal mean?

Answer 22

above the pectinate line the only sensation possible is stretch

Below- temperature, touch and pain sensitive

Question 23

Where do the different parts of the gut hurt?

Answer 23

Question 24

What are some hindgut abnormalities?

Answer 24

Question 25

What structures maintain there mesentaries?

Answer 25

– Jejunum – Ileum – Appendix – Transverse colon – Sigmoid colon

Question 26

What structures of the midgut and hindgut have fused mesentaries?

Answer 26

– Duodenum – Ascending colon – Descending colon – Rectum (no peritoneal covering in distal 1/3)

Question 27

What should happen to the yolk stalk?

Answer 27

Should close up but sometimes doesnt causing the vitelline duct to persist

Question 28

In a patient with pyloric stenosis does the vomit contail bile?

Answer 28

No as bile duct hasnt joined that high up