Lecture 3- Embryology of gut development 1 Flashcards
what are we left with after gastrulation
trilaminar disc
reorganisation from a ball of cells to an organised organism made up of three layers
- ectoderm
- mesoderm
- endoderm
mesoderm can be further split into the
- pariax mesoderm
- intermediate mesoderm
- lateral plate mesoderm
paraxial mesoderm turns into
somites
- skeletal muscle
- vertebra
- cartilage
intermediate mesoderm
kidneys and gonads
- Later plate mesoderm
- Somatic – body walls
- Splanchnic – visceral
ectoderm
- Epidermis (nails, skin etc)
- Nerve tissue
- Endoderm epithelia of the gut
name the two folds that must occur during embryologival folding that must occur for the GI tract to form
- Cranio-caudal folding
- Lateral folding
what does craniocaudal folding result in
head and tail end
what does lateral folding result in
formation of a gut tube
cranio-caudal folding from the saggital plane
duct between the midgut and yolk sac is called
Vitellline duct.
If the vitelline duct doesn’t disappear by birth then there can be a number of problems:
- Mechels diverticulum- outpouching (think diverticulitis)
- Or a connection vetween the umbicilus and the gut (poo may come out belly button)
lateral folding in the transverse plane
yellow endodermal layer becomes
the gut tube
the red mesodermal layers
fuse to form body walls
blue ectodermal layer fuses forming skin and neural tissue
the somatic portion of the lateral plate mesoderm and the ectoderm forms the
somatopleuric mesoderm= body walls and dermis
splanchnic portion of the lateral late mesoderm form the light pink walls
endoderm and splanchnic portion= splanchnopleuric mesoderm= viscera
- splanchnic forms visceral layer of perintoenum
which embryonic structure forms the furture abdiominal and thoracic cavity
intraembryonic coelom= cavity lined by a serous membrane e.g. peritoneum derived from the lateral plate mesoderm
foregut is
the oesophagus to the second part of the duodenum where the bile ducts joints
midgut is from the second part of the duodenum to 2/3s along the way of the transverse colon
hindgut
transverse colon–> rectum
just after folding finises we have
- Gut tube closed at the head and tale end after cranio-caudal folding
membrane that closes the cranio end of the gut tube
buccopharyngeal (4th week rupture)
membrane that closes the caudal end of the gut tube
cloacal membrane (7th week rupture)
after the gut tube is formed how are we orientated in regards to the yolk sac 9yellow thing)
how is the foregut branch supplies by the aorta
coeliac artery
how is the midgut supplied by the aorta
superior emsenteric artery
how is the hindgut supplied by the aorta
inferior mesenteric artery
summary table of the constituents of the F, M and H
formation of the foregut from 4th week
- At week 4 the lung bud forms anteriorly (ventrally)
- Between the lung bud and the foregut a tracheoesophageal septum forms cleaves the respiratory bud which means the trachea and oesophagus are separate
- Possible problems that can occur
- Blind end oesophagus
- Tracheoesophageal fistula
- Possible problems that can occur
- Between the lung bud and the foregut a tracheoesophageal septum forms cleaves the respiratory bud which means the trachea and oesophagus are separate
- At the 5th week the endoderm proliferates to occlude lumen and then it recanalizes at the 9th week
- If any of this fails sections of the gut will be closed – problems
formation of the stoamch
- The stomach is a dilation of the foregut, with the posterior/ dorsal part more dilated
- Inferior part of the stomach rotates 90 degrees superiorly
- The superior part rotates clockwise
stomach folding continued
*this cross section is looking at the foregut section which has both a dorsal mesentery and a ventral mesentery- the rest of the gut only has a dorsal mesentery*
parietal pleura is from the
somatic protion of the alteral mesoderm and can localise pain
visceral pleura is from the
splanchinc (think gut) portion - vague pain
after stomach folding
another budding from the foregut forms
- Cranial portion of the bud= liver
- Caudal portion- gall bladder
folding of the foregut
- The dorsal and ventral mesenteries of the foregut fold clockwise
- At this stage the liver (ends up on the right) is growing much more rapidly than the spleen (ends up on the left)
- Peritoneal cavity (potential space) forms the greater and lesser sac after this folding
- Lesser sac forms lies posterior to the stomach
- The lesser sac and greater sac only come into contact at the free edge (foramen of windslow connection between the lesser and greater sac) , which forms when moving into the midgut region where there is no ventral mesentry
lesser sac ;oes
posterior to the stomach
The lesser sac and greater sac only come into contact at
the free edge (foramen of windslow connection between the lesser and greater sac) , which forms when moving into the midgut region where there is no ventral mesentry
what happens to the right and left vagus nerve during foregut golfing
- It moves along with the liver and spleen 90 degrees
- Left vagus nerve becomes the anterior vagal trunk
- Right vagus nerve becomes the posterior vagul trunk
after foregut folding and birth what happens to the ventral mesentry
- Wall of the abdomen to the liver- falciform ligament
- Portion between the liver and stomach= the less amentum
after foregut folding and birth what does the dorsal mesentry become
Dorsal mesentry becomes
- Connection between the stomach and spleen- gastrosplenic ligament
- Connection between the spleen and retroperitoneal cavity becomes the splenorenal ligament (lieno-renal)
the pancreas development
Pancreas develops as two buds in the ventral (smaller) and dorsal (bigger) mesentery .
- When rotation of the foregut occurs we find that the ventral part (off the hepatic diverticulum) is forced round the back and inferior to the dorsal larger bud
- Eventually the smaller (ventral) and large bud fuse including the ductal systems
