Development of the GI tract

Question 1

Week 1

Answer 1

Fertilization to implantation

Question 2

Week 2

Answer 2

The bilaminar embryo (2 germ layers)

Question 3

Week 3

Answer 3

The trilaminar embryo (3 germ layers)

Question 4

Weeks 4–8

Answer 4

The embryonic period

Question 5

Months 3–9

Answer 5

The foetal period

Question 6

Week 3 - the 3 germ layers

Answer 6

• Endoderm
• Mesoderm
• Ectoderm

Question 7

What occurs after gastrulation?

Answer 7

The formation of the foregut, midgut and hindgut.

Question 8

Blastopore

Answer 8

Opening to the exterior / anus

Question 9

Blastula ->

Answer 9

Gastrula

Question 10

What does the endoderm layer become x4

Answer 10

1. Digestive system
2. Liver
3. Pancreas
4. Lung (inner layers)

Question 11

What does the mesoderm layer become x4

Answer 11

1. Circulatory system
2. Lungs (epithelial layers)
3. Skeletal system
4. Muscular system

Question 12

What does the ectoderm layer become x4

Answer 12

1. Hair
2. Nails
3. Skin
4. Nervous system

Question 13

Foregut arterial

Answer 13

Coeliac trunk

Question 14

Foregut arterial

Answer 14

Coeliac trunk

Question 15

Midgut arterial

Answer 15

Superior mesenteric artery

Question 16

Hindgut arterial

Answer 16

Inferior mesenteric artery

Question 17

Coeliac trunk

Answer 17

• Ab. oesophagus
• Stomach
• Duodenum
• Liver
• Spleen
• Pancreas
• Gallbladder

Question 18

Superior mesenteric artery organs

Answer 18

• Duodenum
• Small intestine
• Caecum
• Appendix
• Ascending colon
• Right 2/3 transverse colon

Question 19

Inferior mesenteric artery supplies

Answer 19

• Left 1/3 of transverse colon
• Rectum
• Anal canal
• Descending colon
• Sigmoid colon

Question 20

What occurs during week 3?

Answer 20

The flat trilaminar embryonic disk becomes a more cylindrical embryo that occurs as a result of embryonic growth forming body cavities.

Question 21

What folding leads to the formation of the gut?

Answer 21

Dorsal / ventral and lateral folding of the embryo

Question 22

What is the membrane that turns into the mouth?

Answer 22

Oropharyngeal (buccopharyngeal) membrane

Question 23

What is the membrane that turns into the anus?

Answer 23

Cloacal membrane

Question 24

What occurs at 22 days?

Answer 24

• Gut-associated organs begin to form as buds from the endoderm, including the thyroid, lung, liver, pancreas
• Midgut opening to the yolk sac progressively narrows

Question 25

What occurs by the end of the first month? x 3

Answer 25

- The stomach bulge is visible - Dorsal pancreas has begun to bud - Connection of the midgut to the yolk sac is reduced to a yolk stalk

Question 26

What does lateral folding of the embryo complete?

Answer 26

The gut tube via the formation of body cavities

Question 27

What occurs at the lateral plate?

Answer 27

The mesoderm splits into splanchnic and somatic mesoderm

Question 28

What does the splanchnic (visceral) mesoderm line?

Answer 28

Lines the gut continuous with yolk sac (viscera walls)

Question 29

What becomes the mesentery?

Answer 29

Somatic mesoderm

Question 30

What does the somatic mesoderm line?

Answer 30

The body cavity (body wall)

Question 31

Where does the foregut extend from?

Answer 31

The buccopharyngeal membrane to the septum transversum

Question 32

What is the buccopharyngeal membrane?

Answer 32

The septum between primitive mouth and pharynx

Question 33

What is the septum transversum?

Answer 33

The precursor to diaphragm and ventral mesentery

Question 34

Through what does the midgut communicate with the yolk sac?

Answer 34

Vitellein tube

Question 35

Where does the hindgut extend to?

Answer 35

The cloacal membrane

Question 36

Where is the cloacal | membrane? and what will it become?

Answer 36

Where ectoderm and endoderm are in contact – will become anus

Question 37

What does the hindgut communicate with?

Answer 37

The allantoic diverticulum

Question 38

What does the allantoic diverticulum become? x 2

Answer 38

The allantois, which becomes the urachus – medial umbilical ligament

Question 39

What is the first functioning intra-embryonic blood vessel?

Answer 39

Dorsal aortae

Question 40

What supplies the pharynx? (foetus)

Answer 40

Aortic arches