Embryology of the Gut and Lungs

212 Functional AnatomyStuart Bunt

Embryonic Curvature traps part of the yolk sac inside the embryo to form the gut.

Embryology of Gut

Lung Buds from the Gut

Stages of Lung Development

Physiological hernia The large liver takes up abdominal space

Intestine lengthens into umbilicus

Rotates as it grows out and again as it re-enters abdomen Omphalocele....no re-entry Umbilical hernia, goes back out covered

in peritoneum

Complex adult layout due to 270o rotation Foregut, Midgut and Hindgut suspended by the dorsal

mesentary, initially straight Ventral mesentary connects stomach and ant. abd. wall, rest

of gut free anteriorly Mesentary supplies blood and nerves to gut between layers of

peritoneum

Stomach rotates and distends

FrontFront

BackBack

OmentumOmentum

Dorsal Dorsal MesentaryMesentary

VentralVentralMesentaryMesentary

Splenic Splenic tissuetissue

Epiploic Epiploic ForamenForamen

Liver and spleen form in mesentary

LiverLiver

SpleenSpleen

StomachStomach

11

22

4a4a4b4b

1. Falciform ligament1. Falciform ligament

2. Lesser Omentum2. Lesser Omentum

3. Dorsal mesentary, divided into:-3. Dorsal mesentary, divided into:-

4a. Gastrosplenic ligament4a. Gastrosplenic ligament

4b. Lienorenal ligament4b. Lienorenal ligament33

AnteriorAnterior

PosteriorPosterior

Formation of Omentum

90 degrees rotation

180 degrees rotation

Final 90 - 270 degrees in total

Blood Supply of the Gut Celiac trunk

Foregut Midgut

Superior mesenteric artery

Hindgut Inferior mesenteric

artery Rectum

Internal iliac artery (pudendal and rectal arteries)

Celiac trunk Foregut Midgut

Superior mesenteric artery

Hindgut Inferior mesenteric artery

Rectum Internal iliac artery

(pudendal and rectal arteries)

Blood Supply to Abdominal

Organs

Canalisation of the Gut

Peritoneum

Flattened endothelial cells on fibro-elastic connective tissue

Parietal and visceral layers Makes gut watertight Suspends gut Contains nerves and blood vessels Omentum contains infection

Flattened Endothelial cellFlattened Endothelial cell

Mesenteries are important:-

Paracolic gutters channel fuid

Stop herniation due to bipedal posture

Supply blood/nerves Sensitive to stretch Contain infection Useful in surgery

Intra and Retroperitoneal

To prevent the intestines falling into the pelvis our upright posture has been accompanied by a fusion of parts of the gut tube to the posterior abdominal wall. These parts become retro-peritoneal.

Uro-rectal septum divides the bladder and urogenital sinus from the rectum