GI Embryology

Question 1

the cranial end of the primordial gut is initially closed by the ______ a the ______

the caudal end is initially closed by the ______ at the ______

Answer 1

oropharyngeal membrane at the stomodeum

cloacal membrane at the proctodeum

Question 2

the primordial gut is derived from (2)

Answer 2

endoderm (most of gut, epithelium, and glands)

splanchnic mesenchyme (muscle, connective tissue)

Question 3

what are the regional differences (3) of the primordial gut, and what genes are they established by?

Answer 3

foregut, midgut, and hindgut

Sonic hedge hog (Shh) and Indian hedge hog (Ihh) genes

Question 4

Derivatives (7) of the foregut and their blood supply*

*except which 3?

Answer 4

primordial pharynx
lower respiratory system
esophagus
stomach
duodenum (up to bile duct)
liver and biliary apparatus
pancreas

supplied by celiac trunk

*except for pharynx, lower resp., and most of esophagus

Question 5

esophagus is intially formed by week ___ and is recanalized during week ___

Answer 5

7

8

Question 6

anomaly that is a blockage of the esophageal lumen - can be a result of failure of recanalization

Answer 6

esophageal atresia

Question 7

in stomach development, a dilation in the foregut appears in week ___ and enlarges __________ (direction)

Answer 7

4

ventrodorsally

Question 8

_____ border of stomach grows quicker leader to _________ of the stomach

Answer 8

dorsal

greater curvature

Question 9

stomach enlarges and rotates ___________, causing these 4 changes

Answer 9

90 degrees clockwise

lesser curvature moves right, greater moves left

cranial end moves left, slightly inferior

caudal end moves right, slightly superior

vagus nerve innervation

Question 10

anterior wall of stomach is innervated by ____

posterior wall of stomach is innervated by ______

(steering wheel is top-down view)

Answer 10

left vagus nerve

right vagus nerve

Question 11

anomaly caused by hypertrophy of pyloric muscles, obstructing food

Answer 11

congenital hypertrophic pyloric stenosis

Question 12

duodenum develops form which regions of primordial gut?

Answer 12

caudal part of foregut and cranial part of midgut

Question 13

blood supply to duodenum (2)

Answer 13

celiac trunk

superior mesenteric

Question 14

duodenum rotates with stomach to lie

Answer 14

right and retroperitoneally

Question 15

anomaly caused by incomplete recanalization of duodenum

Answer 15

duodenal stenosis

Question 16

complete occlusion of duodenum; amniotic fluid absorption is prevented; presence of “double bubble sign” on ultrasound

Answer 16

duodenal atresia

Question 17

derivatives of midgut (5) and blood supply

Answer 17

small intestine
cecum
appendix
ascending colon
right 2/3 of transverse colon

supplied by superior mesenteric artery

Question 18

what is the midgut loop?

Answer 18

ventral u-shaped loop that projects into the proximal part of the umbilical cord due to limited room in abdominal cavity

Question 19

cranial limb of midgut loop forms:

caudal limb of midgut loop forms:

Answer 19

small intestine with rapid growth - jejunum and ileum

cecal diverticulum and appendix

Question 20

physiological umbilical herniation (midgut loop) happens in what week?

Answer 20

6

Question 21

midgut loop rotates __________ around __________

bringing cranial limb to the ____ and caudal limb to the _____

Answer 21

90 degrees counterclockwise

superior mesenteric artery

left; right

Question 22

when do intestines return to abdomen?

Answer 22

10 weeks

Question 23

back in the abdomen, the large intestine continues __________ rotation to form ________

Answer 23

180 degree counterclockwise

right side of abdomen

Question 24

midgut anomaly:

herniation of abdominal contents into umbilical cord; failure of body walls to fuse at umbilical ring

Answer 24

congenital omphalocele

Question 25

midgut anomaly:

umbilicus not closed; intestines herniate; appears during crying or straining

Answer 25

umbilical hernia

Question 26

midgut anomaly:

remnant of proximal portion of omphaloenteric duct along border of ileum; can become inflamed and symptoms mimic appendicitis

Answer 26

Ileal diverticulum - Meckel’s diverticulum

Question 27

“split stomach”

viscera protrude into the amniotic cavity

Answer 27

Gastroschisis

Question 28

cecum develops as a dilation of the _____

Answer 28

caudal midgut loop

Question 29

appendix first starts as

Answer 29

a small diverticulum off cecum

Question 30

variations in final locations of appendix (3)

Answer 30

medial side
retrocecal
rectrocolic

Question 31

derivatives of hindgut (5) and blood supply

Answer 31

left 1/3 of transverse colon
descending colon
sigmoid colon
rectum
superior part of anal canal

supplied by inferior mesenteric artery

Question 32

what is the cloaca

Answer 32

expanded end of hindgut before division into rectum, bladder, and primordial genitalia

Question 33

in partitioning of the cloaca, the _______ grows caudally to meet the ________ and form the ______ body

Answer 33

urorectal septum

cloacal membrane

perineal

Question 34

cloacal partitioning divides cloaca into (2)

Answer 34

anal canal dorsally

urogenital sinus ventrally

Question 35

superior 2/3 of anal canal derived from _____

inferior 1/3 of anal canal derived from ______

Answer 35

hindgut

proctodeum

Question 36

what is the pectinate line?

Answer 36

irregular line of tissue where the two regions of the anal canal meet

Question 37

hindgut anomaly:

dilated part of colon; failure of peristalsis preventing intestinal movement

Answer 37

congenital megacolon (Hirschsprung disease)

Question 38

hindgut anomaly:

thin layer of tissue separates anal canal from exterior

Answer 38

membranous atresia of anus
aka

imperforate anus