Gi Devo

Front 1

Which tissue layer gives rise to the epithelial components of thet gut?

Back 1

endoderm

Front 2

Which gut structures arise from the splanchnic mesoderm

Back 2

msucle, connective tisssue, and other layers of gut wlal

Front 3

Which tissue gives rise to the enteric nervous system

Back 3

ecoderm derived neural crest lineage

Front 4

Describe how the foregut, midgut, and hindgut are first formed.

Back 4

Following gastrulation, small indentations called the foregut and hindgut diverticula form and elongate into two tubes. The tubes fuse into one straight tube consisting of the foregut, midgut, and hindgut

Front 5

What structues arise from the foregut

Back 5

eipthelium of the esophagus, stomach, proximal duodenum, thyroid, lung, liver, and pancrease

Front 6

what structures arise from the midgut

Back 6

small intesintal epithelum

Front 7

What structures arise from the hindgut

Back 7

large intestine epithelum (note some is midgut)

Front 8

Explain the final position of the vagus nerves as a result of stomach rotation

Back 8

Intially the vagus nerves are on the right and left sides of teh stomach. At 7 weeks the stomach rotates 90 clockwise moving the left vagus nerve to the front and the right to the back

Front 9

List thre conseques of the 90 degree clockwise stomach rotation

Back 9

1. repositioning of the vagus nerve (left to ventral, right to dorsal)
2. Repositioning of the greater curvature (dorsal to left) and lesser curvature (ventral to right)
3. creatin of the lesser sac

Front 10

where is the junction between the foregut and midgut endoderm

Back 10

In the duodenum distal to the bile duct

Front 11

As the midgut elongates during the 5th week it forms a U shaped tube wit h cranial and caudal limbs. Which definitive structures do each of these limbs give rise to

Back 11

cranial= distal duodenum, jejunum and most of ilium
caudaul=distal ileum, cecum, appendix, ascending and 2/3 of transverse colon

Front 12

What is the result of the first 90 counterclockwise rotation of the midgut. (occurs about the SMA)

Back 12

The cranial limb is now on the right and the caudal is on the left

Front 13

What is the result of the 180 counterclockwise rotaion of the midgut that occurs during retraction

Back 13

The cranial limb is moved to the left and the caudal occupies the right. This sets up the proper anatomical location of the organs

Hint: the caudal gives rise to the appendix which is on the right side of the body, caudal=tail, apendix looks like a tail

Front 14

What marks the division between the midgut and hindgut derived transverse colon

Back 14

Transition of blood suppy from SMA to IMA

Front 15

What structure partitions the cloaca

Back 15

urorectal septum

Front 16

partitioning of the cloaca by the urorectal septum results in...

Back 16

a rectum on the dorsal side and the urogenital sinus on the ventral side

Front 17

In addition to forming the anal canal and UG sinus, the urorectal septum partitions the cloacal sphincter into

Back 17

1. anal sphincter
2. muscles of superfiical pouch (sup. transverse perineal, bulbospongiousus, ishiocavernosus)

Front 18

Which two tissues give rise to the anal canal

Back 18

superior= hingut
inferior- proctodeum which is ectodermally derived

Front 19

Describe the formation of the hepatic diverticulum
What structures are involved?
What type of cells are formed?

Back 19

1. Foregut endoderm protudes into septum transversum mesenchyme
2. Simple columnar epithelum transform into pseudostratified epithelium withing basement membrane
3. The basment membrane is degreaded and bipotential heatoblasts migrate into the septum transversum mesenchyme forming cords of hepatic cells which differentiate inot hepatocyes or cholangiocytes.

Front 20

Describe the role of growth factors in the formation of the hepatic diverticulum (liver bud)
What structures secrete the growth factors

Back 20

Growth factors such as FGFs and BMPs secreted from the heart and septum transversum and essential for proper specification and outgrowth. Additionlly, a necklace of nedotheial cells is required.

Front 21

Describe the formation of the gall bladder

Back 21

forms from caudal region of liver bud.The stalk of the bud forms the cystic duct, the stal connecting the hepatic and cystic ducts becomes the bile duct which is carried to the dorsal aspect of the duodenum

Front 22

What structures give rise to the pancrease

Back 22

two buds emanating from the dorsal and venral foregut endoderm

Front 23

Describe the cell signaling invovled with the formation of the dorsal pancreatic bud
Where are the signals coming from?

Back 23

-Signals from the notochord such as FGF2 and activin inhibit sonic hedgehog and shift develoment to pancrease instead of intestine.
-Later, the aorta sends out signals to promote bud expansion and endocrine cell diffentiation.
-Exocrine cell differntiation is induced as mesenchyme comes between the aorta and dorsal pancrease

mnemonic: Sonic hedgehoc has spines on his DORSUM that have to be inhibited for pancrease to grow.

Front 24

Describe the cell signaling involved with the formation of the ventral pancreatic bud
What tissues are sending these signals?

Back 24

Unlike the dorsal bud, this region is devoid of sonic hedgehog. Signals from splanchnic mesoderm and vitelline viens are needed for expansion and differentiation of the endocrine and exocrine cell lineages

Front 25

What is the default developmental track of the ventral foregut endoderm? How does it adopt an alternative form?

Back 25

The defaul state is thought to be pancreatic. It gives rise to the liver rather than the pancrease because of exposure to FGFs and BMPs from the cardiac and septum transversum mesenchyme

Front 26

Duodenal atresia or stenosis is caused by ____?
What are the signs in a newborn? How can it be detected prenatally

Back 26

Duodenal atresia/ stenosis is caused by a failure to recanalize the duodenum. Blockage results in vomiting of the stomach contents and bile (the bile is important because it distingushes the cause of vomiting form esophageal atresia) Prenatally, polyhydramnios occurs becasue the fetus cannot swallow and absorb amniotic fluid.

Front 27

What is extrahepatic biliary atresia? What sxs occur after birth

Back 27

-obliteration of the bile ducts
-jaundice, acholic stools

Front 28

What causes gastroschisis

Back 28

defect lateral to the median plane of the anterior abdominal wall. The abdominal viscera is extrubed through the wall without involving the umbilical cord

Front 29

Which is worse, omphalocele or gastroschisis

Back 29

Kind of a trick question
gastroschisis is worse for the intestestines because they are extruded without a membrane are therefore vulnerable to serositis. Omphalocele is worse overall for the baby because it is often assocaited wit hother congenital abnormalities

Front 30

T/F gastroschisis is a hernia

Back 30

false, it is not a hernia because the viscera is not covered in a sac. it is an eviceration

Front 31

What causes omphalocele

Back 31

herniation of the abdominal contents into the proximal umbilicus, results form failure of the intestine to return to the abodomen. Often associated with other abnormalities

Front 32

What is a meckel diverticulum? What is the cause? Sxs?

Back 32

An outpocketing of the ileum as a remnant of the omphaloenteric duct (aka vitteline aka yolk sac).
In other words: Failure of the yolk sac to obliterate/ failure of illeum to return to its proper position

The wall of the diverticulum contains all layers of the ileum and may also contain gastric and pancreatic tissues which is bad because their enzymes are secreted leading to ulcernation and bleeding.

Front 33

Describe Hirschsprung disease

Back 33

Aganglionosis of the colon. Presents as megacolon with the healthy part being enlarged. Dilation results because the affected tissue fails to relax preventing movment of bowl contents