Gut Development 2

Question 1

The primitive gut tube is formed from the … sac in folding of the embryo. The …. membrane is cranial and caudally the diverticula ends with the … membrane

Answer 1

Yolk
Buccopharyngeal
Cloacal

Question 2

What happens when the midgut elongates quickly and no longer fits in the abdominal cavity?

Answer 2

Makes a loop with a cranial and a caudal limb. This physiologically herniates into the umbilicus with the superior mesenteric artery as its axis.

Question 3

What connects the midgut loop and the yolk sac?

Answer 3

The vitelline duct.

Question 4

In which week is the growth of the primary loop very rapid?

Answer 4

6

Question 5

In week 6 which other organ grows quickly meaning there isn’t enough room for it and the fast growing mid gut?

Answer 5

The liver

Question 6

How many degrees must the herniation turn to get the correct orientation of midgut viscera?

Answer 6

270 degree rotation with both cranial and caudal ends fixed.

Question 7

After rotation of the midgut herniation what must depend?

Answer 7

Cacecal bud

Question 8

What embryological problem would give rise to a left sided colon?

Answer 8

Incomplete rotation (midgut only rotates 90 degrees)

Question 9

Reversed midgut rotation results in what visceral arrangement?

Answer 9

Transverse colon posterior to duodenum

Question 10

What is the risk of a midgut abnormality and when would these problems most likely present?

Answer 10

Increased bowel mobility can lead to volvulus that can strangulate and become ischaemic. If a midgut defect is a problem its commonly seen in the neonatal period. (note a lot are asymptomatic)

Question 11

If the caecal bud doesn’t descent what defect is seen?

Answer 11

Subhepatic caecum

Question 12

List three issues that involve persistence of the vitelline duct.

Answer 12

Vitelline cyst
Vitelline fistula
Meckels diverticulum

Question 13

What is the problem with Meckel’s diverticulum?

Answer 13

Risk of volvulus from the out pouching of midgut
Can contain epigastric or pancreatic tissue - secretions cause inflammation as the midgut is not equipped for these foregut tissues secretions

Question 14

What would leak out of the belly button after a Vitelline fistula (yolk sac remnants)?

Answer 14

Intestinal contents

Question 15

Why does meckel’s diverticulum follow the rule of 2s.

Answer 15

2% of population
2 feet from ileocaecal valve
detected usually in under 2s
2:1 male to female

Question 16

Where is the cell growth of gut structures so fast that it closes the lumen and later requires recannulisation?

Answer 16

Oesophagus, buke duct and the small intestine

Question 17

Incomplete recannulisation leads to what defects?

Answer 17

Atresia (obliterated lumen) or stenosis (narrow lumen)

Question 18

What other than failure to reconciles may give rise to atresia or stenosis?

Answer 18

vascular incidents

Question 19

What is pyloric stenosis?

Answer 19

Hypertrophy of the smooth muscle at the pyloric sphincter - not a recannulisation error. Common in infants and leads to projectile vomiting.

Question 20

What is gastroschisis?

Answer 20

Failure of anterior abdominal wall closure during embryonic folding. Uncovered gut tube derivatives outside the body cavity seen antenatally.

Question 21

How would you deliver a baby with gastroschisis?

Answer 21

C section

Normally isolated condition so only risk is a small amount of bowel necrosis- monitor and treat.

Question 22

A persistence of physiological midgut herniation leading to gut material being seen in a translucent membrane protruding from the umbilicus is called what?

Answer 22

Omphalocoele/ exopmphalos

Question 23

How would you distinguish between exomphalos and a umbilical hernia?

Answer 23

Umbilical hernia is covered by skin and subcutaneous tissue. Important to distinguish as umbilical hernias tend to self resolve, but ompahlocoele is not generally an isolated defect.

Question 24

The urinary bladder epithelium is derived from which embryological gut segment?

Answer 24

hindgut

Question 25

What is the pectinate line?

Answer 25

A division in the anal canal between two histologically different regions of the canal with different, vascular, lymphatic and nervous supplies.

Question 26

What is the proctodeum?

Answer 26

Junction of two embryonic germ layers - the urorectal septum meets the proctodeum (or anal pit) to form the septum. The proctodeum is endoderm and ectoderm (cloacal membrane) and forms the distal anal canal.

Question 27

Above the pectinate line what is the neuromuscular supply of the anal canal?

Answer 27

S2,3,4 (parasympathteics)

Inferior mesenteric artery

Question 28

Where do anal canal lympatics above the pectinate line drain to?

Answer 28

internal iliac nodes

Question 29

What epithelium is seen in the proximal anal canal (above pectinate line)?

Answer 29

simple collumnar

Question 30

The pudenal artery and the pudenal nerve together with S2,3,4 supply which part of the anal canal?

Answer 30

The distal part / below pectinate line

Question 31

The superficial inaugural lymph nodes drain which part of the anal canal?

Answer 31

Below pectinate line

Question 32

What sensation can be felt above the pectinate line?

Answer 32

Stretch only

Question 33

Where in the anal canal is temperature, touch and pain sensitive?

Answer 33

Below the pectinate line

Question 34

Is visceral pain poorly or well localised?

Answer 34

Poorly and will reflect the pattern of development for that structure

Question 35

A connection between the rectum and the bladder is called a?

Answer 35

Hind gut fistula

Question 36

Failure of the anal membrane to rupture results in an?

Answer 36

Imperforate anus

Question 37

Anorectal agenesis is ?

Answer 37

failure of the hind gut to meet the proctodeum.

Question 38

Which mid and hindgut structures retain mesenteries?

Answer 38

jejunum, ileum, appendix, transverse colon, sigmoid colon

Question 39

Duodenum, Ascending colon, descending colon, rectum will all fuse their …. in development

Answer 39

mesentries