Embryology

Question 1

what is embryology period?

Answer 1

Week 0-8

Question 2

how do you form the Gut Tube?

Answer 2

1) lateral folding (axial section)
- the disc is rolled up.

2) craniiocaadal folding (sagital section)
= roll it up like a scroll head to toe

Question 3

what are the origins of GIT?

Answer 3

1) endoderm
- epithelium of mucosa
- associated ducts and glands

2) visceral mesoderm
- lamina propra
- muscularis mucosa and muscularis externa
- CT of submucosa and external CT

Question 4

what are the 2 mesenteries of the gut?

Answer 4

1) dorsal and mesenteries

Question 5

what brings the mesenteries into their final position?

Answer 5

= rotation of different parts of gut

Question 6

when is the oesophagus diistinguishable?
when does circular muscle develop?
when does longitudinal muscle develop?

Answer 6

by end of week 4

Circular = week 5

Longitudinal = week 8

Question 7

at the end of week 4, what happens to the caudal part of foregut?

Answer 7

dilation of caudal part of foregut

Question 8

then what happens to the dorsal border?

Answer 8

= grows rapidly

- greater and lesser curvatures

Question 9

describe the rotation about both longitudinal and AP axes?

Answer 9

= 90degree rotation

Question 10

what does growth and rotation of stomach create?

Answer 10

creates the lesser sac and causes the dorsal mesentery to bulge

Question 11

what does contused growth of dorsal mesentery form?

Answer 11

= forms the greater omentum

Question 12

what do the lesser omentum and falciform ligament form from?

Answer 12

ventral mesentery

Question 13

what parts of the duodenum and covered by caudal portion of foregut?

Answer 13

parts 1 and 2

Question 14

what part of duodenum is covered by cranial portion of midget?

Answer 14

parts 3 and 4

Question 15

what is the duodenal loop directed to?

Answer 15

the right due to rotation of stomach

Question 16

what does liver bud grow into?

Answer 16

mesoderm of septum transverse

Question 17

what is the spleens derivative?

Answer 17

mesoderm derivative (not gut tube)

Question 18

when does the spleen develop?

Answer 18

in 5th week

Question 19

what is spleen initially?

Answer 19

haematopoeitc

Question 20

what does the spleen develop into during weeks 15-18?

Answer 20

into lymphatic organs

Question 21

describe the appearance of spleen?

Answer 21

= lobular, but lobes normally regress before birth

- notches in adult

Question 22

which part of the duodenum is the midgut?

what does the midgut contain?

Answer 22

= 2nd part;

Contains

• Ileum
• Jejunum
• Caecum and appeasing
• Ascending colon

Question 23

what part of the transverse colon is the midgut?

Answer 23

proximal 2/3rd

Question 24

when does the midgut communicate with old sac along itslength?

Answer 24

beginning week 4

Question 25

what happens in the middle of week 4?

Answer 25

= connection with yolk sac narrows

Question 26

when is the connection of yolk save via narrow vitelline duct?

Answer 26

end of week 4

Question 27

what happens in week 5?

Answer 27

= midgut has outgrowth embryo and bulges ventrally

Question 28

describe midguts rotation?

Answer 28

= rotates 90degress around an axis of SMA | - Caecal bud has formed on caudal limb

Question 29

what are jejunal-ileal loops?

Answer 29

= small intestine starts to fold on itself

Question 30

what sprouts an appendix?

Answer 30

caecum

Question 31

when does re-entry to the body cavity occur?

Answer 31

= during week 10

Question 32

what returns first during re-entry of body cavity?

Answer 32

- small intestine

Question 33

what else happens during re-entry to body cavity?

Answer 33

= further 180degree rotation - jejunum displaced left and ileum right t - descending colon pushed left - transverse colon pushed superiorly

Question 34

what is last to re-enter?

Answer 34

caecum

Question 35

when does formation of definitive gut lumen occur?

Answer 35

week 5/6 = proliferation of mucosa

Question 36

what happens to the lumen during formation of definitive gut lumen?

Answer 36

= lumen becomes occluded

Question 37

after lumen becomes occluded, what develops over next 2 weeks?

Answer 37

= vacuoles

Question 38

what is complete by week 9?

Answer 38

= re-canalisation