GI system

what type of tissue is the endothelial lining of the digestive tract and parenchyma of glands made of

endoderm

what is the connective tissue for glands, muscle, connective tissue and peritoneal components of the gut wall made of

visceral mesoderm

what structures have endoderm origins

epithelium of the mucosa and it associated ducts and glands

what structures have visceral mesoderm origins

lamina propria, muscularis mucosa and externa and connective tissue of the submucosa and external connective tissue

what structures have neural crest origins

enteric nervous system, Meissner’s plexus and Auerbach’s plexus

when does Meissner’s plexus present

week 8

when does Auerbach’s plexus present

week 12

what is part of the foregut division of the gut tube

oropharyngeal membrane to the liver outgrowth

what is the foregut supplied by

coeliac artery

what is part of the midgut division of the gut tube

caudal to liver bud to 2/3rds along the transverse colon

what is the midgut supplied by

superior mesenteric artery

what is part of the hindgut division of the gut tube

last 1/3rd of the transverse colon to cloacal membrane

what is the hindgut supplied by

inferior mesenteric artery

what happens by week 5 in regards to the gut tube

gut tube is connected to the dorsal body wall by the dorsal mesentery

what is the ventral mesentery derived from

septum transversum

what is the ventral mesentery divided by the liver into

ventral mesogastirum and the falciform ligament

when does the oesophagus become distinguishable

by the end of week 4

when does the circular muscle of the oesophagus develop

week 5

when does the longitudinal muscle of the oesophagus develop

week 8

what happens in week 4 with regards to stomach formation

stomach starts as a fusiform dilation

how is the greater curvature formed

rapid growth of the dorsal wall

how is the lesser curvature formed

slow growth of the ventral wall

how does the stomach rotate

90 degrees clockwise around the longitudinal axis and anteroposterior axis rotation

what does the longitudinal rotation of the stomach result in

dorsal mesogastrium moving to the left, which creates the omental bursa behind the stomach, and pulls the lesser omentum to the right

how is the greater omentum formed

when the anteroposterior rotation occurs the dorsal mesogastrium bulges and grows downwards forming a double layered sac over the transverse colon and small intestines. the 2 layers will fuse to form a single sheet

how does the duodenum move when the stomach rotates

moves from the midline to the right side of the abdominal cavity

what happens in the middle of week 3 with regards to liver formation

the liver bud appears as an ventral outgrowth of the foregut

how is the bile duct formed

by the connection between the liver bud and the foregut narrowing

what does the ventral outgrowth of the bile duct give rise to

gallbladder and cystic duct

what are the hepatic sinusoids formed from

liver cords, vitelline veins and umbilical veins

what do liver cords become

liver cells(parenchyma) and the lining of the biliary ducts

what does the septum transversum become in the liver

hematopoietic cells, Kupfer cells and connective tissue cells

what is the pancreas formed from

dorsal pancreatic bud and the ventral pancreatic bud of the duodenum

what does duodenal rotation result in

ventral pancreatic bud moving below and behind the dorsal pancreatic bud

how does the dorsal pancreas connect to the duodenum

through the minor duodenal papilla

how does the ventral pancreas connect to the duodenum

through the major duodenal papilla

when does the spleen differentiate from the dorsal mesogastrium

during week 5

what happens to the spleen during weeks 15-18

changes from a haematopoietic structure into a lymphatic organ

what happens to the midgut at the beginning of week 4

communicating with the yolk sac along its length

what happens to the midgut in the middle of week 4

the connection with the yolk sac narrows

what happens to the midgut at the end of week 4

its connected to the yolks sac via a narrow vitelline duct

what happens to the midgut in week 5

it has outgrown the embryo and bulges ventrally

when does the physiological umbilical herniation occur

during week 6

what happens during the physiological umbilical herniation

the intestinal loops move through the umbilical cord to lie outside the embryo

how does the midgut rotate

90 degrees clockwise, then during week 10 it loops another 180 degrees

when do the jejunal-ileum loops finish looping

around week 8

what is the positions of all the parts of the midgut once it has retracted back into the abdomen

the jejunum is displaced left and the ileum to the right, the descending colon is pushed left and the transverse colon is pushed superiorly, the caecal bud descends to the iliac fossa

what is the cloaca

an endoderm lined cavity covered by ectoderm at the ventral surface

what is the cloacal membrane

the boundary between ectoderm and endoderm

what is the urorectal septum

a wedge of mesoderm that grows to separate the cloaca into the urogenital sinus anteriorly and anorectal canal posteriorly

what happens to the hindgut in week 7

the cloacal membrane ruptures creating openings for the hindgut posteriorly and the urogenital sinus anteriorly

what is the lower 1/3rd of the anal canal composed of

proctodeum- ectoderm invagination

what is the upper 1/3rd of the anal canal composed of

endoderm of the hindgut

what is the middle 1/3rd of the anal canal composed of

degeneration of the cloacal membrane

what is the pectinate line

the junction of endoderm and ectoderm