Gastrointestinal Embryology Flashcards
Exposure to teratogens is most harmful when?
Weeks 4-8
Organogenesis occurs during which weeks?
3-8
What occurs during gastrulation?
Bilaminar –> Trilaminar disk
Ectoderm forms what?
Epidermis, CNS, PNS, retina, adrenals
Endoderm forms what?
GIT, Resp, glands, liver, pancreas
Mesoderm forms what?
CVS, connective tissue, muscles, bone marrow
Primordial gut arises when?
Week 4
What closes the primordial gut at the cranial end?
Oropharyngeal membrane
What closes the primordial gut at the caudal end?
Cloacal membrane
What separates the esophagus and the lung buds?
Tracheo-esophageal septum
How is the foregut attached to the walls?
Dorsal and ventral mesogastrium
Where does the liver develop?
Ventral mesogastrium (which becomes the lesser omentum)
Where does the spleen develop?
Dorsal mesogastrium (becomes the greater omentum)
What is the name of the opening leading from the greater omentum to the lesser omentum?
Epiploic foramen
Incomplete separation of the laryngo-tracheal tube causes what?
Esophageal atresia + tracheo-osophageal fistula
When does the foregut dilate to form the stomach?
Week 4
What causes the curvatures of the stomach?
Differential growth
What rotation occurs to form the stomach?
Anterio-posterior rotation
How does rotation cause the formation of the lesser sac (omental bursa)?
Rotation along the longitudinal axis pulling the dorsal mesentery to the left
Duodenum is formed from what embryonic structures?
Caudal foregut
Dorsal midgut
What causes the C-shape of the duodenum?
Rotation of the stomach
Which part of the duodenum is intraperitoneal?
Duodenal cap
When does the liver primordium bud appear?
Middle of 3rd week
The liver bud grows into what structure?
Septum transversum
How is the bile duct formed?
Connection between the liver bud and the foregut
Formation of the gall bladder grows how?
Ventral outgrowth of the bile duct
The primordial spleen is differentiated from what?
Mesenchymal condensation of the dorsal mesogastrium
Spleen is derived from what?
Mesoderm
The spleen acts as what until week 14?
Haemopoietic organ
The spleen is colonised by what from weeks 15-17\?
T-lymphocytes
The spleen gains what at week 23?
B-cell precursors
Lymphoid function
The pancreas forms when? From what?
Week 5
Endodermal lining of duodenum
How does the pancreas form?
Two buds which come to fuse
If the ventral bud fails to migrate around the duodenum, it may cause what?
Annular pancrease
–> duodenal stenosis
The midgut starts and ends where?
Distal duodenum
Proximal 2/3rds transverse colon
The Cephalic part of the primary intestinal loop becomes what?
Distal duodenum
Jejunum
Proximal ileum
The caudal part of the primary intestinal loop becomes what?
Distal ileum
–> Proximal 2/3rds tranverse colon
When does the rotation of the midgut occur?
Week 6
The rotation of the primary intestinal loop occurs around what? In which direction?
Axis of superior mesenteric artery
90degrees anti-clock
What happens as the rotation occurs?
The gut tube herniates into the embryonic cavity of the umbilical cord
When does the midgut reenter the abdominal cavity?
Week 10
What enters first?
Jejunum –> caecum
What rotation occurs as the herniated loops reenter the cavity?
180degree anti-clockwise
Failure to retract the umbilical loops causes what?
Omphalocele
Herniation of abdominal contents into the amniotic cavity is what?
Gastrochisis
Remnants of the vitelline duct causes what? Could form what?
Meckel’s diverticulum
Vitelline cyst
Fistula
Lining of the bladder and urethra are formed of what?
Hindgut endoderm
What is the cloaca?
Endoderm lined cavity with surface ectoderm
What do you find at the cloacal membrane?
Endoderm/ectoderm boundary
When does the cloacal membrane rupture?
Week 7
When does the anal canal re-open?
Week 9
Incomplete separation from the hindgut in the urorectal septum causes what?
Fistulas
