Lecture 3- Embryology of gut development 1

Question 1

what are we left with after gastrulation

Answer 1

trilaminar disc

reorganisation from a ball of cells to an organised organism made up of three layers

• ectoderm
• mesoderm
• endoderm

Question 2

mesoderm can be further split into the

Answer 2

• pariax mesoderm
• intermediate mesoderm
• lateral plate mesoderm

Question 3

paraxial mesoderm turns into

Answer 3

somites

• skeletal muscle
• vertebra
• cartilage

Question 4

intermediate mesoderm

Answer 4

kidneys and gonads

Question 5

• Later plate mesoderm

Answer 5

• Somatic – body walls
• Splanchnic – visceral

Question 6

ectoderm

Answer 6

• Epidermis (nails, skin etc)
• Nerve tissue

Question 7

• Endoderm epithelia of the gut

Question 8

name the two folds that must occur during embryologival folding that must occur for the GI tract to form

Answer 8

1. Cranio-caudal folding
2. Lateral folding

Question 9

what does craniocaudal folding result in

Answer 9

head and tail end

Question 10

what does lateral folding result in

Answer 10

formation of a gut tube

Question 11

cranio-caudal folding from the saggital plane

Answer 11

Question 12

duct between the midgut and yolk sac is called

Answer 12

Vitellline duct.

Question 13

If the vitelline duct doesn’t disappear by birth then there can be a number of problems:

Answer 13

• Mechels diverticulum- outpouching (think diverticulitis)
• Or a connection vetween the umbicilus and the gut (poo may come out belly button)

Question 14

lateral folding in the transverse plane

Answer 14

Question 15

yellow endodermal layer becomes

Answer 15

the gut tube

Question 16

the red mesodermal layers

Answer 16

fuse to form body walls

Question 17

blue ectodermal layer fuses forming skin and neural tissue

Question 18

the somatic portion of the lateral plate mesoderm and the ectoderm forms the

Answer 18

somatopleuric mesoderm= body walls and dermis

Question 19

splanchnic portion of the lateral late mesoderm form the light pink walls

Answer 19

endoderm and splanchnic portion= splanchnopleuric mesoderm= viscera

• splanchnic forms visceral layer of perintoenum

Question 20

which embryonic structure forms the furture abdiominal and thoracic cavity

Answer 20

intraembryonic coelom= cavity lined by a serous membrane e.g. peritoneum derived from the lateral plate mesoderm

Question 21

foregut is

Answer 21

the oesophagus to the second part of the duodenum where the bile ducts joints

Question 22

midgut is from the second part of the duodenum to 2/3s along the way of the transverse colon

Question 23

hindgut

Answer 23

transverse colon–> rectum

Question 24

just after folding finises we have

Answer 24

• Gut tube closed at the head and tale end after cranio-caudal folding

Question 25

membrane that closes the cranio end of the gut tube

Answer 25

buccopharyngeal (4th week rupture)

Question 26

membrane that closes the caudal end of the gut tube

Answer 26

cloacal membrane (7th week rupture)

Question 27

after the gut tube is formed how are we orientated in regards to the yolk sac 9yellow thing)

Answer 27

Question 28

how is the foregut branch supplies by the aorta

Answer 28

coeliac artery

Question 29

how is the midgut supplied by the aorta

Answer 29

superior emsenteric artery

Question 30

how is the hindgut supplied by the aorta

Answer 30

inferior mesenteric artery

Question 31

summary table of the constituents of the F, M and H

Answer 31

Question 32

formation of the foregut from 4th week

Answer 32

* 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 * At the 5^th week the **endoderm proliferates to occlude lumen** and then it recanalizes at the 9^th week * If any of this fails sections of the gut will be closed – problems

Question 33

formation of the stoamch

Answer 33

* 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**

Question 34

stomach folding continued

Answer 34

\*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\*

Question 35

parietal pleura is from the

Answer 35

somatic protion of the alteral mesoderm and can localise pain

Question 36

visceral pleura is from the

Answer 36

splanchinc (think gut) portion - vague pain

Question 37

after stomach folding

Answer 37

another budding from the foregut forms * Cranial portion of the bud= **liver** * Caudal portion- **gall bladder**

Question 38

folding of the foregut

Answer 38

* 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

Question 40

lesser sac ;oes

Answer 40

posterior to the stomach

Question 41

The lesser sac and greater sac only come into contact at

Answer 41

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

Question 42

what happens to the right and left vagus nerve during foregut golfing

Answer 42

* 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**

Question 43

after foregut folding and birth what happens to the ventral mesentry

Answer 43

* Wall of the abdomen to the liver- **falciform ligament** * Portion between the liver and stomach= t**he less amentum**

Question 44

after foregut folding and birth what does the dorsal mesentry become

Answer 44

**Dorsal mesentry becomes** * Connection between the stomach and spleen- gastrosplenic ligament * Connection between the spleen and retroperitoneal cavity becomes the splenorenal ligament (lieno-renal)

Question 45

the pancreas development

Answer 45

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