GI Tract Development

Question 1

what is the lining from the oro-pharynx to the anal canal?

Answer 1

epithelium derived from endoderm

Question 2

what is the epithelial tube surrounded by?

Answer 2

splanchnic mesoderm

Question 3

what does splanchnic mesoderm form?

Answer 3

forms the muscle and connective tissue layers, blood vessels and peritoneal components (mesothelium and connective tissue)

Question 4

primitive gut tube formatin

Answer 4

folding results in a portion of the endoderm lined yolk sac to be incorporated into the embryo as the primitive gut tube

Question 5

endoderm derivatives

Answer 5

rise to the epithelial cells of the gut tube

-pharyngeal foregut, digestive system, and respiratory system

Question 6

splanchnic mesoderm derivatives

Answer 6

smooth muscle, connective tissue, blood vessels, visceral epithelium

Question 7

how does the midgut communicate with the yolk sac?

Answer 7

via the vitelline duct which becomes the core of the umbilical cord

Question 8

dorsal mesentary

Answer 8

it is bi-layered and suspends the abdominal viscera in the body cavity (intraembryonic body cavity)

Question 9

ventral mesentary

Answer 9

connects stomach and liver to the ventral body wall

Question 10

how is the primordial gut closed?

Answer 10

by the ends of the oropharyngeal membrane and the cloacal membrane

Question 11

artery of the foregut

Answer 11

celiac trunk

Question 12

foregut range

Answer 12

pharyngeal - buccophaaryngeal membrane to respiratory diverticulum
proper- caudal to pharyngeal tube to superior duodenum and superior to ampulla of the pancreatic duct

Question 13

midgut artery

Answer 13

superior mesenteric artery

- inferior duedenum and RIGHT 2/3 of the transverse colon

Question 14

midgut range

Answer 14

inferior to the bile duct/pancreatic duct to the junction of the right 2/3 and left third of the transverse colon

Question 15

hindgut artery

Answer 15

inferior mesenteric artery - left one third of the transverse colon to the rectum upper anal canal

Question 16

hindgut range

Answer 16

left third of the transverse colon to the cloacal membrane

Question 17

esophagus development

Answer 17

develops at the ventral wall of the foregut, below the pharynx and elongates rapidly due to the descent of the heart and lungs

Question 18

upper 1/3 of esophagus

Answer 18

muscle fibers are derived from myotomes and is striated muscularis externa

Question 19

lower 2/3 of esophagus

Answer 19

muscle fibers are smooth muscle and derived from the splanchnic mesoderm mesencyme

Question 20

esophagotracheal septum

Answer 20

partitions the trachea from the esophagus

Question 21

foregut/stomach rotation how/endpoint and what causes it

Answer 21

stomach rotates 90 degrees clockwise around the longitudinal axis

• differential growth
• creates the greater and lesser curvature of the stomach

Question 22

what do the stomach rotations do to the duodenum?

Answer 22

bend it into a C shape and displace it to the right and most of it becomes secondarily retroperitoneal (adhered to body wall)

Question 23

blood supply (artery) to the duodenum

Answer 23

celiac artery and the superior mesenteric artery
upper = foregut
lower = midgut

Question 24

what happens to pancreas when stomach rotates and where is it derived

Answer 24

also becomes put into a retro-peritoneal position with the duodenum and it is derived from endoderm

Question 25

hepatic diverticulum

Answer 25

initial growth of the liver and gall bladder | from an endodermal thickening on the ventral aspect of the duodenum

Question 26

what does the hepatic diverticulum grow into?

Answer 26

septum transversum

Question 27

2 divisions of the hepatic diverticulum

Answer 27

1. larger cranial portion gives rise to the PRIMORDIAL OF THE LIVER and a connection of the diverticulum and gut tube maintained becomes the bile duct 2. a smaller, ventral outgrowth of the BILE duct gives rise to the gallbladder and the cystic duct

Question 28

bile duct

Answer 28

recieves from hepatic duct from liver and also cystic duct from the gallbladder

Question 29

gallbladder

Answer 29

ventral outgrowth of the bile duct that will also give rise to the cystic duct

Question 30

pancreas

Answer 30

initially a ventral and dorsal bud originating from the endoderm of the duodenum. when the gut rotation occurs it brings the ventral bud to the left and dorsal and FUSION occurs. the common bile duct will also move dorsal

Question 31

what junction marks end of foregut and beginning of midgut?

Answer 31

JUCNTION OF THE PANCREATIC DUCT AND THE COMMON BILE DUCT - both emptying into the duodenum

Question 32

main pancreatic duct

Answer 32

main duct of ventral bud and distal part of the duct of the dorsal bud VENTRAL =MAIN

Question 33

accessory pancreatic duct

Answer 33

proximal part of the dorsal bud that regresses can remain as the accessory pancreatic duct

Question 34

primitive umbilical ring

Answer 34

junction of embryonic ectoderm and the amnion

Question 35

At week 5 what structures pass through the primitive umbilical ring?

Answer 35

1. connecting stalk with umbilical vessels 2. yolk stalk (connects midgut and yolk sac) 3. canal connecting intra and extraembryonic cavities 4. wharton's jelly - protects blood vessels (extracellular support) 5. yolk sac is in the chorionic cavity

Question 36

yolk stalk

Answer 36

connects the midgut and yolk sac

Question 37

major event in development of midgut (when and what)

Answer 37

physiological HERNIATION of the midgut around WEEK 6. the intestinal loops enter the extraembryonic cavity

Question 38

what causes the midgut/ umbilical herniation?

Answer 38

continued midgut elongation (growth of the small intestine is more rapid and greater than the growth of the abdomen there is also rapid growth and expansion of the liver (abdominal cavity at this stage is too small for all the organs

Question 39

hindgut gives rise to what structures

Answer 39

``` left 1/3 of the transverse colon descending colon sigmoid colon rectum upper anal canal ```

Question 40

the endoderm of the hindgut also forms the...

Answer 40

epithelial lining of the bladder and urethre

Question 41

how does the descending colon become retroperitoneal?

Answer 41

the dorsal mesentary SHORTENS

Question 42

stroma of liver and gall bladder

Answer 42

septum transversum and splanchnic mesoderm