Embryology Flashcards
what is embryology period?
Week 0-8
how do you form the Gut Tube?
1) lateral folding (axial section)
- the disc is rolled up.
2) craniiocaadal folding (sagital section)
= roll it up like a scroll head to toe
what are the origins of GIT?
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
what are the 2 mesenteries of the gut?
1) dorsal and mesenteries
what brings the mesenteries into their final position?
= rotation of different parts of gut
when is the oesophagus diistinguishable?
when does circular muscle develop?
when does longitudinal muscle develop?
by end of week 4
Circular = week 5
Longitudinal = week 8
at the end of week 4, what happens to the caudal part of foregut?
dilation of caudal part of foregut
then what happens to the dorsal border?
= grows rapidly
- greater and lesser curvatures
describe the rotation about both longitudinal and AP axes?
= 90degree rotation
what does growth and rotation of stomach create?
creates the lesser sac and causes the dorsal mesentery to bulge
what does contused growth of dorsal mesentery form?
= forms the greater omentum
what do the lesser omentum and falciform ligament form from?
ventral mesentery
what parts of the duodenum and covered by caudal portion of foregut?
parts 1 and 2
what part of duodenum is covered by cranial portion of midget?
parts 3 and 4
what is the duodenal loop directed to?
the right due to rotation of stomach
what does liver bud grow into?
mesoderm of septum transverse
what is the spleens derivative?
mesoderm derivative (not gut tube)
when does the spleen develop?
in 5th week
what is spleen initially?
haematopoeitc
what does the spleen develop into during weeks 15-18?
into lymphatic organs
describe the appearance of spleen?
= lobular, but lobes normally regress before birth
- notches in adult
which part of the duodenum is the midgut?
what does the midgut contain?
= 2nd part;
Contains
- Ileum
- Jejunum
- Caecum and appeasing
- Ascending colon
what part of the transverse colon is the midgut?
proximal 2/3rd
when does the midgut communicate with old sac along itslength?
beginning week 4
what happens in the middle of week 4?
= connection with yolk sac narrows
when is the connection of yolk save via narrow vitelline duct?
end of week 4
what happens in week 5?
= midgut has outgrowth embryo and bulges ventrally
describe midguts rotation?
= rotates 90degress around an axis of SMA
- Caecal bud has formed on caudal limb
what are jejunal-ileal loops?
= small intestine starts to fold on itself
what sprouts an appendix?
caecum
when does re-entry to the body cavity occur?
= during week 10
what returns first during re-entry of body cavity?
- small intestine
what else happens during re-entry to body cavity?
= further 180degree rotation
- jejunum displaced left and ileum right t
- descending colon pushed left
- transverse colon pushed superiorly
what is last to re-enter?
caecum
when does formation of definitive gut lumen occur?
week 5/6 = proliferation of mucosa
what happens to the lumen during formation of definitive gut lumen?
= lumen becomes occluded
after lumen becomes occluded, what develops over next 2 weeks?
= vacuoles
what is complete by week 9?
= re-canalisation
