GI Embryology

Question 1

What gene is a transcription factor for establishing left sidedness?

Answer 1

PTX2

Question 2

Which week does the trimlaminar germ disk form?

Answer 2

Week 3

Question 3

What are the three phases of embryonic development?

Answer 3

Growth/proliferation
Morphogenesis
Differentiation

Question 4

What happens during gastrulation?

Answer 4

Bilaminar embryonic disc converted into trilaminar disc

Question 5

What is formed from embryonic ectoderm?

Answer 5

Skin, CNS, PNS, epithelia of eye/ear/nose, liver, adrenal medulla

Question 6

What is formed from embryonic endoderm?

Answer 6

Epithelial lining of reproductive system, GIT, glands, liver, pancreas, thyroi, bladder etc.

Question 7

What is formed from embryonic mesoderm?

Answer 7

Muscle, bones, cartilage, dermis, vascular system, urogenital system except bladder, spleen, suprarenal gland cortex

Question 8

What mesoderms arise from the lateral plate mesoderm?

Answer 8

Parietal and visceral mesoderm

Question 9

What weeks does the gut tube form in?

Answer 9

Week 3 + 4

Question 10

What is the gut tube closed by at the cranial end?

Answer 10

Oropharyngeal membrane

Question 11

What is the gut tube closed by at the caudal end?

Answer 11

Cloacal membrane

Question 12

What does the foregut develop from?

Answer 12

Cranial part of the primitive gut tube

Question 13

What structure develops from the ventral wall of the foregut?

Answer 13

Laryngo-tracheal diverticulum (lung bud)

Question 14

What divides the foregut tube into the trachea and oesophagus?

Answer 14

Tracheo-esophageal septum

Question 15

In what week does the foregut dilate to form the stomach?

Answer 15

4th week

Question 16

What rotation does the stomach undergo around its own longitudinal axis?

Answer 16

90’

Question 17

What is the final rotation the stomach undergoes to create the final position?

Answer 17

Anterio-posterior rotation

Question 18

What is the stomach attached to both the dorsal and ventral wall by?

Answer 18

Mesogastrium

Question 19

What is the duodenum formed from?

Answer 19

Caudal part of the foregut and cranial part of the midgut

Question 20

What is the blood supply of the duodenum?

Answer 20

Coeliac trunk and SMA

Question 21

What shape does the duodenum become as the stomach rotates?

Answer 21

C-shaped

Question 22

When does the liver bud appear?

Answer 22

Middle of 3rd week

Question 23

What does the liver bud grow into?

Answer 23

Septum transversum

Question 24

What does the liver bud develop from?

Answer 24

Outgrowth of endoderm in distal end of foregut

Question 25

What does the connection between the liver bud and foregut narrow to form?

Answer 25

Bile duct

Question 26

What does the ventral outgrowth from the bile duct form?

Answer 26

Gall bladder and cystic duct

Question 27

During which week does a mesenchymal condensation develop into the spleen?

Answer 27

5th week

Question 28

What is a spleen a derivative of?

Answer 28

Mesoderm

Question 29

Up until which week does the spleen act as a haemopoietic organ?

Answer 29

Week 14

Question 30

During weeks 15-17, what is the spleen colonised by?

Answer 30

T-lymphocytes

Question 31

During which week do B-cell precursors arrive at the spleen?

Answer 31

Week 23

Question 32

At what week can the spleen start its lymphoid function and why?

Answer 32

Week 23 - B-cell precursors arrive

Question 33

How many buds does the pancreas grow from?

Answer 33

2

Question 34

What does the pancreas grow from and when?

Answer 34

Endodermal lining of the duodenum | Week 5

Question 35

What can result if there is incomplete separation of the laryngo-tracheal tube?

Answer 35

Esophageal atresia | Tracheo-oesophageal fistula

Question 36

What happens if the ventral bud fails to migrate around the duodenum properly?

Answer 36

Annular pancreas

Question 37

What might happen if there is an annular pancreas?

Answer 37

Duodenal stenosis

Question 38

What does development of the midgut involve?

Answer 38

Rapid elongation of the gut tube = primary intestinal loop

Question 39

What does the cephalic part of the primary intestinal loop become?

Answer 39

Distal duodenum, jejunum and proximal ileum

Question 40

What does the caudal part of the primary intestinal loop become?

Answer 40

Distal ileum, caecum, appendix, ascending colon and proximal 2/3rds transverse colon

Question 41

When does rotation of the midgut begin?

Answer 41

6th week

Question 42

Where does initial rotation of the primary intestinal loop occur and how does it rotate?

Answer 42

Around the axis of the SMA | 90' anti-clockwise

Question 43

What else happens to the midgut apart from initial rotation?

Answer 43

Physiological herniation

Question 44

Where does the midgut herniate?

Answer 44

Into the extraembryonic cavity in the umbilical cord

Question 45

When does the intestinal loop move from the umbilical cord back into the abdominal cavity?

Answer 45

10th week

Question 46

What is omphalocele?

Answer 46

Herniation of abdominal viscera through an enlarged umbilical ring and failure of retraction of umbilical ring

Question 47

What is gastrochisis?

Answer 47

Herniation of abdominal contents directly through body wall into amniotic habit and not covered by peritoneum/amnion Through weak area right of umbilicus

Question 48

What does vitelline duct form?

Answer 48

Meckel's diverticulum

Question 49

What is Meckel's diverticulum a remnant of?

Answer 49

Vitelline duct

Question 50

What does the endoderm of the hindgut also form?

Answer 50

Bladder and urthra lining

Question 51

What does the terminal portion of the hindgut join with?

Answer 51

Posterior part of the cloaca

Question 52

What does the allantois enter?

Answer 52

Anterior part of the cloaca

Question 53

What is the cloaca?

Answer 53

Endoderm lined cavity with surface ectoderm at its ventral boundary

Question 54

What can be a result of incomplete separation of the hindgut from the urogenital sinus by the urorectal septum?

Answer 54

Urorectal fistula Rectovaginal fistula Rectoanal fistula Imperforate anus