GI embryo

Question 0

what is in the foregut

Answer 0

Resp tree esophagus stomach proximal duodenum pancreas + ducts liver + gall bladder

Question 1

what is in the midgut

Answer 1

distal duodenum jejunum ileum cecum ascending colon first half of transverse colon

Question 2

what is in the hidngut

Answer 2

last part of transverse colon descending colon sigmoid colon proximal 2/3 rectum

Question 3

what is dorsal mesentery made of? function? what does it give rise to?

Answer 3

• Dorsal mesentery connects gut tube with posterior abdominal wall • Mesentery carries blood vessels from the aorta to the gut tube • Continuous from cranial to caudal end gives rise to Greater omentum - 4 layered pocket hanging below stomach, superficial to ab organs

Question 4

what is ventral mesentery made of? gives rise to?

Answer 4

ventral mesentery connects gut tube to the anterior body wall liver liver develops in ventral mesentery and grows into 2 parts: 1) anterior -Falciform ligament 2) posterior - Lesser Omentum with the Hepatoduodenal LIgament and Heptogastric Ligament ventral mesentery ONLY IN FOREGUT

Question 5

Dorsal segmental arteries

Answer 5

supplies somites/muscle mass gives rise to posterior intercostals

Question 6

Lateral segmental arteries

Answer 6

supply developing kidneys gives rise to renal arteries

Question 7

Ventral segmental arteries

Answer 7

supply gut tube, through dorsal mesentery. initially paired, some drop out or fuse. 3 unpaired ventral arteries remain: celiac artery (foregut) SMA (midgut) IMA (hindgut)

Question 8

describe the development of intestines

Answer 8

around 4-5 weeks the intestines are growing rapidly - gut tube grows faster than peritoneum so the intestines bulge out ventrally into umbilicar cord around weeks 8-9, there is enough room so intesttines come back in as intestines re-enter peritoneal cavity, they rotate 270 degrees counterclockwise around the Vitelline Duct/SMA. brings structures into their position - LI is anterior/framing the SI. cecum will but up near liver but will grow down. cecum elongates without growing wider - forms vermiform appendix

Question 9

describe types of clinical issues due to Malrotation of Gut

Answer 9

1) Non rotation - 2) Reversed Rotation - Situs Inversus. OK if everything flips. 3) Subhepatic cecum - cecum does not grow down and remains at liver

Question 10

Omphalocele

Answer 10

gut tube does not retrat, remains in the umbilical cord and covered in amnion

Question 11

Gastroschisis

Answer 11

like omphalocele (gut tube does not retract out of the umbilical cord like it sholud) however, guts are NOT covered in amnion

Question 12

Meckel’s Diverticulum?

Answer 12

vitelline duct normally closes/dissolves after guts retract. Vitelline duct remains and you get outpocketing of the SI

Question 13

Fibrous Cord?

Answer 13

vitelline duct remains and forms a fibrous cord. guts anchored to anterior wall and cant move

Question 14

Umbilicoileal Fistula

Answer 14

vitelline duct remains and forms a cord with a lumen - chyme can leak out!

Question 15

Volvulus?

Answer 15

vitelline duct remains and twists

Question 16

subhepatic cecum?

Answer 16

type of issues due to malrotation of the intestines cecum does not grow down like it should, remains up near liver

Question 17

what is urorectal septum

Answer 17

in development the urogenital and digestive systems have a common outflow tract called Cloaca - we need to separate Urorectal Septum - tissue between allantois and hindut that grows down and forms the Anorectal canal and urogenital sinus

Question 18

how does liver form? what signals?

Answer 18

High BMP and FGF will tell endoderm to be liver BMP from septum transversum FGF from cardiogenic plate

Question 19

what signals forms pancreas? ventral and dorsal?

Answer 19

Low BMP and FGF - default tissue is ventral pancreas Dorsal pancreas develops on the other side of gut tube in presence of Shh

Question 20

what signals form exocrine vs. endocrine pancreas? cells within endocrine?

Answer 20

Exocrine pancreas - Notch sensitive Endocrine pancreas - Notch insensitive Pax 6 - Alpha (glucagon) and Gamma (PP) cells Pax 4 - beta (insulin) and delta (SS) cells - Develop LATER

Question 21

what is Annular Pancreas

Answer 21

Ventral pancreatic bud does not move properly - can surround/narrow the duodenum

Question 22

Coelom ? Development of

Answer 22

Intraembryonic coelom will give rise to thoracic and abdominal cavities Coelom = space lined by epithelium but derived from mesenchyme In the lateral plate mesoderm, a space develops between the somatic and splanchinc mesoderm layers. EEC = Extraembryonic Coelom = Chorion Cavity Over time IEC and EEC fuse - only in areas where there are somites. Lateral folding will form defined IEC and close it Cephalocaudal folding will get rid of EEC.

Question 23

what are the 4 parts of the diaphram?

Answer 23

1. septum transversum 2. Pleuroperitoneal membrane (used to be capsules of mesonphric kidneys) 3. mesentery of esophagus 4. posterior body wall SPEP

Question 24

how does diaphragm develop? (thorax and abomden separation - peritoneal cavity)

Answer 24

as septum transversusm moves down, it hits different strucutres. stops at posterior body wall. Diphragm forms from things septum transversum hits

Question 25

how does pleural cavity and pericardial sac develop/separate?

Answer 25

intussuseption of common cardinal veins - forms a Pleuropericardial membrane