Development of GI

Question 1

What does the foregut make?

Answer 1

Oral cavity, pharynx, lower respiratory tract, esophagus, stomach, liver, gallbladder, pancreas, upper duodenum

Question 2

What does the midgut make?

Answer 2

Lower duodenum, jejunum, ileum, cecum, appendix, ascending colon, proximal 2/3 of transverse colon

Question 3

What does the hindgut make?

Answer 3

distal 1/3 transverse colon, descending colon, sigmoid colon, rectum, upper anal canal

Question 4

What supplies blood to the foregut distal to the diaphragm?

Answer 4

celiac trunk

Question 5

What supplies blood to the midgut?

Answer 5

superior mesenteric artery

Question 6

What supplies blood to the hindgut?

Answer 6

inferior mesenteric artery

Question 7

What are the beginning and end of the primitive gut tube?

Answer 7

Oropharyngeal membrane

Cloacal membrane

Question 8

What connects the gut tube to the yolk sac?

Answer 8

vitelline duct

Question 9

What makes the epithelial lining and glands of the GI tract, excluding the lower 1/3 anus?

Answer 9

endoderm

Question 10

What makes the CT, vasculature and SM walls of the GI tract?

Answer 10

splanchnic mesoderm

Question 11

What makes the epithelium of the lower 1/3 anus and NCC that make enteric ganglia, nerves and glia of GI tract?

Answer 11

ectoderm

Question 12

When does maturaiton of the GI tract begin?

Answer 12

8 weeks

Question 13

When does peristalsis occur?

Answer 13

10 weeks

Question 14

What are the secondary retroperitoneal organs?

Answer 14

ascending colon
descending colon
duodenum
bulk of pancreas

Question 15

When do the ventral and dorsal mesenteries form?

Answer 15

4th week

Question 16

What does the ventral mesentery form?

Answer 16

lesser omentum

• –> hepatoduodenal L
• –> hypogastric L

falciform L

coronary L
triangular L
—>both of liver

Question 17

Where does the ventral mesentery form?

Answer 17

between the body wall and foregut and between the diaphragm and umbilicus

Question 18

Where does the dorsal mesentery form?

Answer 18

suspends diaphragm between lower esophagus to caudal hindgut

Question 19

What does the dorsal mesentery make?

Answer 19

Greater omentum

• ——> gastrosplenic L
• ——-> gastrocolic L
• ——-> splenorenal L

SI mesentery

Transverse mesocolon

Sigmoid mesocolon

Question 20

What makes the SI mesentery?

Answer 20

dorsal mesentery

Question 21

What makes the transverse mesocolon?

Answer 21

dorsal mesentery

Question 22

What makes the sigmoid mesocolon?

Answer 22

dorsal mesentery

Question 23

What makes the greater omentum?

Answer 23

dorsal mesentery

Question 24

What makes the lesser omentum?

Answer 24

ventral mesentery

Question 25

What makes the falciform L?

Answer 25

ventral mesentery

Question 26

What makes the coronary L of the liver?

Answer 26

ventral mesentery

Question 27

What makes the triangular L of the liver?

Answer 27

vental mesentery

Question 28

What makes R and L vagal nerves turn into Posterior and Anterior vagal trunks?

Answer 28

stomach rotation in development

Question 29

What mesenteries is the stomach suspended by prior to rotation?

Answer 29

ventral and dorsal mesenteries

Question 30

Describe rotation of stomach during development

Answer 30

Elongates, rotates 90 degrees so ventral mesentery is RIGHT and dorsal mesentery is LEFT

Question 31

What is the portion of mesentery between the stomach and body wall after stomach rotation?

Answer 31

dorsal mesogastrium

Question 32

What becomes the double-layered apron drape that eventually turns into the greater omentum?

Answer 32

dorsal mesogastrium

Question 33

What does the stomach rotation make in terms of sacs?

Answer 33

lesser sac behind stomach greater sac is continuous with abd cavity

Question 34

Describe hypertrophic pyloric stenosis

Answer 34

pyloric lumen narrows and obstructs food passage -->muscularis external hypertrophies and makes olive at the R costal margin

Question 35

What is the etiology behind pyloric stenosis?

Answer 35

sphincter can't relax d/t faulty NCC migration --->ENS isn't populated correctly

Question 36

What are sx of pyloric stenosis?

Answer 36

non-bilious vomiting few and small stools can't gain weight

Question 37

What makes liver stromal, Kupffer and stellate cells?

Answer 37

splanchnic mesoderm

Question 38

What is the embryonic hematopoietic organ?

Answer 38

liver

Question 39

What organ has rare congenital abnormalities?

Answer 39

liver

Question 40

When does bile begin to form?

Answer 40

week 12

Question 41

Describe liver formation

Answer 41

diverticulum from gut ENDODERM buds--> grows into septum transversum--> differentiates into hepatocytes, bile duct and hepatic ducts

Question 42

What percent of the population has an accessory pancreatic duct?

Answer 42

33%

Question 43

What is pancreatic divisum?

Answer 43

two totally separate ducts, prone to pancreatitis

Question 44

What are you prone to having if you have pancreatic divisum?

Answer 44

Pancreatitis

Question 45

Where do the first endodermal buds of the pancreas form?

Answer 45

dorsal bud in dorsal mesentery | ventral bud in ventral mesentery

Question 46

Do dorsal and ventral buds of the pancreas have exo/endo fxns?

Answer 46

Yes

Question 47

When does the ventral pancreatic bud move to fuse with the dorsal bud?

Answer 47

5th week

Question 48

What does the dorsal pancreatic bud form?

Answer 48

head, body and tail

Question 49

What does the ventral pancreatic bud form?

Answer 49

unicate process

Question 50

What occurs in an annular pancreas?

Answer 50

ventral bud wraps around the duodenum instead of completely migrating to the dorsal bud

Question 51

What does annular pancreas cause?

Answer 51

duodenal obstruction/stenosis BILIOUS vomiting if inferior to bile duct

Question 52

What is the origin of the gallbladder and bile duct?

Answer 52

cystic endoderm

Question 53

Describe how the bile duct forms

Answer 53

initially closed, opens via recanilization

Question 54

Define biliary atresia

Answer 54

obliteration of the extra-/intra-hepatic ducts-->replaced with fibrous tissue d/t inflammation

Question 55

What are the hallmarks of biliary atresia?

Answer 55

progressive jaundice soon after birth white clay stools dark urine

Question 56

What is the treatment for biliary atresia?

Answer 56

liver transplant within 12-19 months of life

Question 57

When does the spleen begin to develop?

Answer 57

4th week

Question 58

Where does the spleen begin to form?

Answer 58

as a mesenchymal condensation in the dorsal mesogastrium

Question 59

What is the spleen populated by during development?

Answer 59

mesoderm populated by myeloid lymphoid cells

Question 60

What are the stages of herniation and re-entry of the midgut during development?

Answer 60

herniates out umbilicus at 6 weeks | comes back in at 10 weeks

Question 61

Describe midgut rotation

Answer 61

1: 90 degree counterclockwise rotation ------> cecum and asc colon on L side of abd cavity 2: 180 degree counterclockwise rotation as it reenters abdomen -------> cecum in RUQ, asc colon anterior to duodenum 3: rest of midgut enters abdomen --------> cecum RUQ, pulls asc colon down to R side --------> transverse colon in front of duodenum and pancreas

Question 62

Describe an omphalocele

Answer 62

herniation of gut continues out of the umbilicus | ****covered with peritoneum

Question 63

What causes an omphalocele?

Answer 63

- bowel doesn't fully retract - abnormal lateral body folding and fusion creates weakness in wall-->herniates - CT of skin and hypaxial M of body wall dont form-->weakness-->herniation

Question 64

Describe gastroschisis

Answer 64

herniation of abdomen contents through abd wall -->not covered by peritoneum so exposed to external environment

Question 65

Describe Meckel's Diverticulum

Answer 65

vitelline duct doesn't degenerate-->midgut still connected to umbilicus

Question 66

List the rule of 2's related to Meckel's Diverticulum

Answer 66

``` 2% incidence 2x more common in males 2% have medical sx 2 feet proximal to terminal ileum 2 inches long 2 years of age ```

Question 67

What are the sx of Meckel's Diverticulum?

Answer 67

abdominal swelling SI obstruction bowel sepsis GI bleeding

Question 68

Describe volvus

Answer 68

rolled up and twisted intestines

Question 69

What do midgut rotation anomalies increase the risk of?

Answer 69

volvus

Question 70

What are sx of gut volvus?

Answer 70

acute abdominal pain omiting GI bleeding

Question 71

What are Trisomy 13 and 18 associated with?

Answer 71

omphalocele

Question 72

What occurs in non-rotation of midgut loop?

Answer 72

only completes the first 90 degree counterclockwise rotation (not the 180)

Question 73

What are the effects of non-rotation of midgut loop?

Answer 73

L sided colon, R sided SI

Question 74

What occurs in a reverse gut rotation?

Answer 74

completes the first 90 degree counterclockwise rotation but then does a 180 degree rotatoin CLOCKWISE --->so only net 90 degree clockwise rotation

Question 75

What are the effects of reverse gut rotation?

Answer 75

transverse colon is posterior to duodenum

Question 76

What are the sx of reverse gut rotation?

Answer 76

ischemia | stenosis of colon

Question 77

Describe intestinal stenosis and atresia

Answer 77

partial occlusion/ ineffective recanalization of intestines OR complete occlusion

Question 78

Why are the intestines closed during the 5-6th months?

Answer 78

endoderm proliferation causes the lumen to close-->recanalizes later

Question 79

What is trisomy 21 associated with?

Answer 79

intestinal stenosis/atresia

Question 80

What does the urorectal septum divide the cloaca into?

Answer 80

dorsal anorectal canal | ventral urogenital sinus

Question 81

The cloaca ruptures after septum proliferates to give _______________

Answer 81

urogenital membrane and anal membrane - ->sinuses open to exterior - -> septum become perineum b/t urogenital and anus

Question 82

What is the function of the anal plug?

Answer 82

temporarily closes anal rectal lumen -->anal pit with ectodermal walls d/t mesenchymal proliferation

Question 83

What is the anal canal made of?

Answer 83

2/3 endodermal epithelium (BV, N of hindgut) | 1/3 ectodermal epithelium (BV, N of anal pit)

Question 84

What BV supply upper anal canal?

Answer 84

superior and middle rectal As

Question 85

What BV supply lower anal canal?

Answer 85

inferior rectal A

Question 86

What divides the hindgut and anal pit?

Answer 86

pectineal line

Question 87

What is the difference between anal canal and anal pit?

Answer 87

anal canal is the hindgut and anal pit anal pit is lower anal canal that butts up to anus

Question 88

What is an imperforated anus?

Answer 88

persistent anal membrane

Question 89

What disease is due to a lack of ganglionic plexus (failure of NCC migration)?

Answer 89

Hirschsprung's disease

Question 90

List possible consequences of abnormal urorectal septum development

Answer 90

``` Persistent anal membrane Anal atresia Anoperineal fistula Rectovaginal fistula Rectourethral fistula Rectovesical fistula ```