GIT Embryology

Question 1

What happens in week 1

Answer 1

Fertilisation to Implantation
5-6 days

Question 2

what happens in week 2

Answer 2

Bilaminar germ disk formation
Everything in 2
Establishment of body axis
PTX2 gives left hand sideness

Question 3

What happens in week 3

Answer 3

Trilaminar germ disk formation

Question 4

What happens in week 3 - 8

Answer 4

Organogenesis

Question 5

What different structures originate from ectoderm

Answer 5

CNS,PNS
Epithelia of eye, ear, nose
SKin
Adrenal medulla
NESA

Question 6

What structures orginate from embryonic endoderm

Answer 6

Epthelia of Resp
GIT
glands
liver
pancreas
thyroid
bladder

Question 7

What structures originate from mesoderm

Answer 7

muscles
bones
cartiladge
dermis
vascular system
spleen,liver

Question 8

When is the gut tube formed

Answer 8

During 3rd and 4th week
Lateral p.m -> parietal & visceral mesoderm
Parietal lines body cavity
Visceral lines gut tube

Question 9

What is the gut tube closed by

Answer 9

Oropharyngeal membrane at Cranial
Cloacal membrane at Cudal end

Question 10

What is the mesentery

Answer 10

Mesodermal origin
Enclose organs
Hangs gut tube

Question 11

Where does the oeophagus develop from

Answer 11

Cranial part of gut tube

Question 12

How is the stomach formed

Answer 12

Foregut caudal to oesophagus dilates = stomach
Week 4
Creates GC and LC

Question 13

Where are the greater and lesser omentum located

Answer 13

Question 14

How is the duodenum formed

Answer 14

From caudal part of foregut
Cranial part of midgut
-Retropertoneal except duodenal cap

Question 15

When is liver bud formed

Answer 15

Week 3

Question 16

What structures are endodermal in origin and mesodermal in origin

Answer 16

Endodermal origin:
Hepatocytes, biliary epithelia
Gall bladder & cystic duct
Mesodermal origin:
Kupffer cells
haematopoeitu and connective tissue

Question 17

What is the origin of spleen
What happens in weeks 15-17 and 23

Answer 17

Mesodermal origin
15-17: T-lymphocytes
23: B-cell arrives- lymphoid function begins

Question 18

What is the origin of pacreas

Answer 18

Endodermal

Question 19

Give an example of developmental anomaly

Answer 19

Incomplete seperation of lung bud
Oesophageal atresia and tracheooesophageal fistula
Duplication of galbladder

Question 21

Midgut

How is the primary intestinal loop formed

Answer 21

Anti-clockwise rotation
Physical herniation of loop
Vitelline duct connects with ilium of yolk sac

Question 22

What are some of the midgut anomalies

Answer 22

Abnormal rotation or reversed rotation

Question 23

What happens during a omphalocele

Answer 23

Failure of retraction of herniated intestinal loop
Week 10

Question 24

What problem can occur with remnants of vitelline duct

Answer 24

May form fistula/cyst/ligament

Question 25

What does atrasia and stenosis look like

Answer 25

Question 26

Hindgut development

What parts of the hindgut are endodermal or ectodermal in origin

Answer 26

Endodermal:
Distal 1/3rd transverse colon
Descending colon
Sigmoid colon
rectum
Ectodermal:
Lower anal canal & anal orrifice

Question 27

What are the different anal canal origins

Answer 27

Cranial part -> endodermal
Caudal part-> ectodermal
cloacal membrane ruptures at 7th week gestation

Question 28

What is the blood supply of hindgut

Answer 28

Question 29

What are the developmental anomalies in hindgut

Answer 29