peritoneal embryology

Question 1

overview of gut tube formation

Answer 1

embryo folding starting in week 3 incorporated endoderm (leading to lining and glands of gut) lined tube from yolk sack creating foregut, midgut, and hind gut; splanchnic mesoderm outside of endoderm leads to smooth muscle, connective tissue and mesentery

Question 2

viteline duct

Answer 2

connects midgut to yolk sac

Question 3

intraembryonic visceral lateral plate mesoderm

Answer 3

is ventral region of intraembryonic coelom, intimate to endoderm, leads to viceral mesothelium after lateral folding

Question 4

intraembryonic parietal lateral plate mesoderm

Answer 4

is dorsal region of intraembryonic coelom, intimate to ectoderm, leads to parietal mesothelium after lateral folding

Question 5

dorsal mesentery

Answer 5

double layer of peritoneum below diaphragm suspending the gut tube from the dorsal body wall from the lower end of the esophagus to the rectum, later as gut grows and rotates, some parts of the dorsal mesentery are lost as portions of the gut fuse to the posterior body wall (parts of duodenum and colon), segmented into smaller parts (eg dorsal mesogastrium)

Question 6

ventral mesentery

Answer 6

extension of septum transcersum, associated only with foregut, liver, biliary tree and ventral pancreas gow into it, double layer of peritoneum derived from the septum transversum and extending from the liver to the ventral body wall (falciform ligament) and from the liver to the stomach and doudunum (lesser omentum)

Question 7

development of the stomach

Answer 7

portion of the foregut caudal to diaphragm starts to gow but at different growth rate, causes the developing stomach to roate to the right and caudal end swings cranially creating curvatures, also effects doudenum and its curviture

Question 8

dorsal mesogastrium

Answer 8

transforms with the stomach rotation, swings out left and ventrally then expands caudally as an out-pocketing (composed of 2 sheets of mesentery), space created behind stomach is omental bursa, 2 sheets of mesentery fuse to form greater omentum

Question 9

distal foregut development

Answer 9

proximal 1/3 of duodenum and hepatic diverticulum grow into ventral mesogastrium (intraperitoneal), distal part of doudenum and head of pancreas press against dorsal body wall with rotation of stomach and dorsal mesoduodenum fuses with adjacent peritoneum (retroperitoneal)

Question 10

hepatic diverticulum

Answer 10

liver bud, outgrowth of distal part of foregut, grows into septum transversum and ventral mesogastrium (forming lesser omentum and falciform ligament respectively), gallbladder and bile ducts arise from hepatic diverticulum

Question 11

pancreas devlopment

Answer 11

formed by two buds growing out of duodenum, ventral pancreatic bud grows into ventral mesoduodenum, dorsal pancreatic bud grows into dorsal mesoduodenum, with rotation of duodenum ventral meets up with dorsal bud and fuse and become retroperitoneal, pancreatic ducts (stem-like) consolidate, proximal portion degenerates if not accessory pancreatic duct

Question 12

bile duct formation

Answer 12

grew into ventral mesogastrium, rotates left and enters duodenum from posterior and left direction

Question 13

midgut

Answer 13

includes distal 2/3 of duodenum to 2/3 of transverse colon

Question 14

midgut loop formation

Answer 14

is still attached to dorsal wall by mesentery, and to yolk sac by vitiline duct, herniates out into the umbilical cord as it elongates and rotates, upper arm is small interstine, lower arm is terminal ileum, cecum, appendix, and colon, returns to abdominal cavity and rotates and folds creating current formation, cecum bud grows out of ileum

Question 15

hindgut

Answer 15

distal 1/3 of transverse colon, descending colon, sigmoind colon and cloaca (rectum and upper anal canal and urogentical sinus)

Question 16

cloaca

Answer 16

common chamber for the hindgut (posterior region) and urinary system (anterior region), seperated by urorectal septum, ectrodermal invagination canalize and connect with hind gut to form anal canal (pectinate line)

Question 17

parasympathetic innervation of GI track

Answer 17

neural crest cells migrate down, including to gi, creating parasympathetic ganglia, if they don’t travel to colon, cant do parastalsis and normal portion dialates (hirschsprung disease)