Embryology

Question 1

How is the gut tube produced

Answer 1

Due to lateral and craniocaudal folding in the 4th week of development

Question 2

What type of mesoderm covers the gut tube

Answer 2

Splanchnic mesoderm

Question 3

What lines the gut tube

Answer 3

Endoderm

Question 4

What 3 areas is the gut tube divided into

Answer 4

Foregut, midgut and hindgut

Question 5

What is derived from the foregut

Answer 5

Oesophagus, stomach, pancreas, liver, gall bladder, part of the duodenum

Question 6

What is derived from the midgut

Answer 6

Duodenum, jejunum, ileum, caecum, ascending colon, transverse colon

Question 7

What is derived from the hindgut

Answer 7

Transverse colon, descending colon, sigmoid colon, rectum, anal canal

Question 8

What blood vessel supplies the foregut

Answer 8

coeliac trunk

Question 9

What blood vessel supplies the midgut

Answer 9

Superior mesentry artery

Question 10

What blood vessel supplies the hindgut

Answer 10

Inferior mesentry artery

Question 11

What are retroperitoneal structures

Answer 11

Those which are not suspended in the abdominal cavity’s peritoneum

Question 12

What are secondary retroperitoneal structures

Answer 12

Structures which were invested in the peritoneum but the mesentry then fused with the posterior abdominal wall, making them retroperitoneal

Question 13

What causes the production of secondary retroperitoneal structures

Answer 13

Rotation of the stomach

Question 14

What is the intraembryonic coelom

Answer 14

The cavity through which the gut tube is suspended in

Question 15

What will the intraembryonic coelom develop into

Answer 15

Thoracic and abdominal cavities

Question 16

What septum separates the the GI tract from the respiratory diverticulum

Answer 16

Tracheoesophageal septum

Question 17

What is a mesentry

Answer 17

Double fold of peritoneum which suspends the gut tube in the intraembryonic coelom

Question 18

How far along the tube does dorsal mesentry run

Answer 18

Along the whole length

Question 19

How long does the ventral mesentry run along the gut tube

Answer 19

Along the foregut

Question 20

why does looping of the midgut and herniation occur

Answer 20

as the midgut elongates massively and it runs out of room

Question 21

what connects the midgut to the yolk sac in the umbilical cord

Answer 21

vitelline duct

Question 22

how does the midgut rotate

Answer 22

around the superior mesenteric artery in 3 90 degree rotations

Question 23

what does the descending of the caecal bud produce

Answer 23

the ascending colon

Question 24

which limb of the midgut loop is pushed back in first after herniation

Answer 24

cranial limb

Question 25

what is a volvulus

Answer 25

twisting of the GI tract, cutting off the blood supply

Question 26

why does recanalisation of the GI tract occur

Answer 26

as there is rapid growth of the cells lining the lumen which would otherwise cause atresia or stenosis

Question 27

is pyloric stenosis a recanalisation failure

Answer 27

no

Question 28

what is pyloric stenosis

Answer 28

where there is hypertrophy of the circular muscle above the pyloric sphincter

Question 29

would the vomit in pyloric stenosis be bilious or non bilious

Answer 29

non bilious as the bile duct has not drained into this prat of the GI tract

Question 30

would the vomit in midgut volvulus be bilious or non bilious

Answer 30

bilious as the bile duct has drained into the GI tract by here

Question 31

what is a vitelline cyst

Answer 31

where the duct forms a fibrous strands connecting the intestines to the abdominal wall

Question 32

what is a vitelline fistulae

Answer 32

where the vitelline duct doesn’t close off, so keeps an opening between the umbilicus and intestines.

Question 33

what is meckels diverticulum

Answer 33

where the vitelline duct doesn’t fully regress, so part remains as a remnant

Question 34

what is the rule of 2s with meckels diverticulum

Answer 34

• affects 2% of the population
• 2:1 male to female ratio
• 2 feet from ileo-ceacal valve

Question 35

what is gastroschisis

Answer 35

where the abdominal wall fails to close during folding so the intestines protrude out

Question 36

what is omphalocoele

Answer 36

where there is persistence of the physiological herniation (when the midgut pushes out of the body and doesn’t go back in) it is covered by peritoneum

Question 37

what is umbilical hernia

Answer 37

where the intestines bulge out at the belly button but are still covered by skin

Question 38

what line divides the 2 regions of the anus

Answer 38

pectinate line

Question 39

from what embryonic layer does the superior portion of the anus derive from

Answer 39

endoderm

Question 40

from what embryonic layer does the inferior portion of the anus derive from

Answer 40

ectoderm

Question 41

where are the innervations for the superior and inferior portions of the anus

Answer 41

superior = visceral innervation (can only detect stretch) 
inferior = somatic innervation (pain, temperature, touch sensitive)

Question 42

what is an imperforate anus

Answer 42

where the anal membrane fails to rupture

Question 43

what is a hindgut fistulae

Answer 43

where there is an abnormal connection of the anus to another organ e.g. the bladder

Question 44

what does the development of the anal canal from 2 different tissues mean for its structure and neurovascular supply

Answer 44

superior = innervated by pelvic parasympathetics, has columnar epithelium, lymph drainage to internal iliac nodes

inferior = innervated by pudendal nerve, has stratified epithelium, lymph drainage to superficial inguinal nodes, vascular supply by pudendal artery