Embryology of the GI

Question 1

What gene is a transcription factor for establishing left sideness?

Answer 1

PTX2

Question 2

What is Gastrulation?

Answer 2

Gastrulation is when the single-layered blastula is reorganised into a multilayered structure known as the gastrula

Question 3

What are the 3 main components for forming the trilaminar germ disk?

Answer 3

Gastrulation

CNS induction

Neurulation

Question 4

What occurs during gastrulation?

Answer 4

The bilaminar disc is converted into the trilaminar disc

Question 5

What are the 3 phases of embryo development

Answer 5

1. Growth/proliferation
2. Morphogenesis
3. Differentiation

Question 6

What are teratogens?

Answer 6

Agent of factor that can cause harm to the embryo e.g. drugs

Question 7

What main drug may cause major congenital anomalies?

Answer 7

Thalidomide

Question 8

What are the components of the trilaminar disc?

Answer 8

Embryonic ectoderm

Embryonic endoderm

Embryonic mesoderm

Question 9

What does the embryonic ectoderm form?

Answer 9

Skin
CNS,PNS 
Sensory epithelia of the eye 
Ear 
Nose 
Sweat glands enamel of teeth 
Liver ( except the parenchyma)
Adrenal medulla 
ETC...

Question 10

What does the embryonic endoderm form?

Answer 10

Epithelial lining of RS
GIT
Glands 
Liver
Pancreas 
Urinary bladder 
ETC...

Question 11

What does the embryonic mesoderm form?

Answer 11

Muscle 
Bones 
Cartilage 
Dermis 
Vascular system 
Urogenital system except bladder 
Spleen 
Suprarenal gland cortex 
ETC...

Question 12

What gives rise to parietal and visceral mesoderm?

Answer 12

Lateral plate mesoderm

Question 13

What does the gut tube form from during the 3rd and 4th week?

Answer 13

The endoderm lining of the yolk sac

Question 14

What forms the urethra and bladder?

Answer 14

Allantois

Question 15

What does the esophagus form from?

Answer 15

Develops from the cranial part of the primitive gut tube

Question 16

What does the Laryngo-tracheal diverculum (lung bud) develop from?

Answer 16

It develops from the ventral wall of the foregut

Question 17

What does the tracheo-esophageal septum (ridge) divide?

Answer 17

Divides the foregut tube (endoderm lined) into trachea and esophagus

Question 18

What happens in the 4th week to the foregut?

Answer 18

The foregut dilates to form the stomach

Question 19

What rotation does the stomach undergo to create a final adult position?

Answer 19

An arterio-posterior rotation

Question 20

The stomach is attached to both the dorsal and ventral wall by a mesentary called what?

Answer 20

Mesogastrium

Question 21

What does rotation along the longitudinal axis pulling the dorsal mesentary to the left create?

Answer 21

The omental bursa (lesser sac)

Question 22

What is pulled to the right during the creation of omental bursa (lesser sac)?

Answer 22

Ventral mesogastrium

Question 23

What does the duodenum form from?

Answer 23

Formed from the caudal part of the foregut and the cranial part of the midgut

Question 24

What is the blood supply of the duodenum formed from?

Answer 24

Formed from the caudal part of the foregut and the cranial part of the midgut

Question 25

What is the blood supply of the duodenum?

Answer 25

Coeliac trunk and superior mesenteric artery

Question 26

What does retroperitoneal mean?

Answer 26

Situated or occuring behind the peritoneum

Question 27

When does the liver bud appear?

Answer 27

Middle of the 3rd week

Question 28

What does the liver bud give rise to?

Answer 28

The liver bud gives rise to the gallbladder and bile ducts, as well as to the parenchyma of the liver

Question 29

What forms the bile duct?

Answer 29

Connection between the liver bud and foregut (duodenum) narrows to form bile duct

Question 30

What forms the gall bladder and cystic duct?

Answer 30

Ventral outgrowth from the bile duct forms the gall bladder and cystic duct

Question 31

What does connective tissue always form from?

Answer 31

Mesoderm

Question 32

Foregut (spleen): What occurs at the end of the 4th week?

Answer 32

A mesenchymal condensation develops in the dorsal mesogastrium near the body wall

Question 33

Foregut (spleen): What occurs during the 5th week?

Answer 33

The mesenchyme differentiates to form the spleen

Question 34

What is spleen derived from?

Answer 34

The spleen is a mesodermal derivative

Question 35

What is a falsiform ligament?

Answer 35

A ligament attaches the liver to the front body wall, and separates the liver into the left lobe and right lobes.

Question 36

What does the pancreas form from?

Answer 36

It forms from the 2 buds, which grow from the endodermal lining of the duodenum in week 5.

Question 37

What 2 things fuse to form the pancreas?

Answer 37

Dorsal and Ventral buds

Question 38

What is the main pancreatic duct composed of?

Answer 38

Ventral duct + Distal part of dorsal duct

Question 39

What occurs if the tracheo-esophageal septum deviates incorrectly?

Answer 39

Then there is an incomplete separation of laryngo-tracheal tube (lung bud)

Question 40

What is it called if the ventral bud fails to migrate around the duodenum correctly?

Answer 40

Annular pancreas - This may cause duodenal stenosis

Question 41

What is the midgut?

Answer 41

The distal part of duodenum, jejunum, ileum, caecum, appendix, ascending colon, proximal 2/3rds of the transverse colon

Question 42

What does the development of the midgut involve?

Answer 42

It involves rapid elongation of the gut tube and its associated mesentary - Described as the 'primary intestinal loop'

Question 43

What part of the primary intestinal loop will become the distal duodenum, jejunum and proximal ileum?

Answer 43

The Cephalic part of the primary intestinal loop

Question 44

What part of the primary intestinal loop becomes the distal ileum, caecum, appendix, ascending colon and the proximal 2/3rds of the transverse colon?

Answer 44

The Caudal part of the primary intestinal loop

Question 45

What week does the rotation of the midgut begin?

Answer 45

6th week know this

Question 46

Where does the initial rotation of the primary intestinal loop occur?

Answer 46

It occurs around the axis of the superior mesenteric artery

Question 47

What is physiological herniation of the midgut?

Answer 47

As the 90 degree rotation occurs, the gut tube herniates into the extraembryonic cavity in the umbilical cord

Question 48

What is Omphalocele?

Answer 48

It is the herniation of abdominal viscera through an enlarged umbilical ring - Failure of retraction of umbilical ring

Question 49

What is Gastrochisis?

Answer 49

Herniation of abdominal contents directly through the body wall into the amniotic cavity - Through a weak area right of umbilicus

Question 50

What does the remnants of vitelline duct form?

Answer 50

Forms meckels's diverticulum - May form fistula or vitelline cyst/ligament

Question 51

What is the hindgut?

Answer 51

Distal 1/3rd of transverse colon, descending colon, sigmoid colon, rectum and upper part of the anal canal. - Endoderm of hindgut also forms the lining of the bladder and urethra.

Question 52

What part of the hindgut joins with the posterior part of the cloaca (primitive anal canal)?

Answer 52

The terminal portion of the hindgut joins with the posterior part of the cloaca.

Question 53

What is the Enoderm/ectoderm boundary?

Answer 53

It is the cloacal membrane

Question 54

What artery supplies the Foregut?

Answer 54

Coeliac artery

Question 55

What artery supplies the Midgut?

Answer 55

Superior mesenteric artery

Question 56

What artery supplies the Hindgut?

Answer 56

Inferior mesenteric artery