Embryology of GI

Question 1

Define Gastrulation

Answer 1

Occurs when a blastula (single layer) folds and enlarges to create a gastrula (three layers)

Question 2

What are the three germ layers of a gastrula

Answer 2

ectoderm, mesoderm, endoderm

Question 3

When does the primordial gut form

Answer 3

4th week

Question 4

What is the cranial end closed by

Answer 4

oropharyngeal membrane

Question 5

What is the caudal end closed by

Answer 5

cloacal membrane

Question 6

What thee parts does the primordial gut tube divide into

Answer 6

foregut, midgut, hindgut

Question 7

Endoderm of the primordial gut forms

Answer 7

most of gut, epithelium and glands

Question 8

Epithelium from cranial and caudal end are derived from

Answer 8

ectoderm (stomodeum) and anal pit (proctodeum)

Question 9

In 4th week the intra-embryonic coelom becomes

Answer 9

embryonic body cavity

Question 10

Embryonic body cavity divides into

Answer 10

Pleural, Pericardial and Peritoneal cavities

Question 11

Primordial pharynx derived from

Answer 11

foregut

Question 12

Lower respiratory tract derived from

Answer 12

foregut

Question 13

Oesophagus derived from

Answer 13

foregut

Question 14

Stomach derived from

Answer 14

foregut

Question 15

Duodenum (part above opening of bile and pancreatic duct) derived from

Answer 15

foregut

Question 16

Liver derived from

Answer 16

foregut

Question 17

Biliary apparatus derived from

Answer 17

foregut

Question 18

Pancreas derived from

Answer 18

foregut

Question 19

Oesophageal Atresia

Answer 19

congenital condition causing oesophagus to end in a blind end pouch. Caused by failure of recanalization

Question 20

Tracheoesophageal fistula

Answer 20

abnormal connection in one or more places between the oesophagus and the trachea. Caused by abnormal deviation of trachea-oesophageal septum

Question 21

What is a coelom

Answer 21

a cavity lined by an epithelium derived from mesoderm (organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks)

Question 22

Three main developments of the stomach

Answer 22

1. Rotation of stomach – Rotates
   90 degree clock wise
2. Mesenteries of stomach
3. Formation of omental bursa (lesser sac)

Question 23

What is hypertrophic pyloric stenosis

Answer 23

blockage of the passage out of the stomach due to thickening (hypertrophy) of the muscle at the junction between the stomach and the intestines - treatment is surgical

Question 24

Development of liver

Answer 24

hepatic diverticular (liver bud) is a cellular extension of foregut endoderm that gives rise to the parenchyma of the liver

Question 25

Liver (duct) anomaly

Answer 25

accessory hepatic ducts (5%)

Question 26

Extrahepatic biliary atresia

Answer 26

one or more bile ducts are abnormally narrow, blocked, or absent

Question 27

Development of pancreas

Answer 27

formation of a ventral and a dorsal pancreatic bud - dorsal pancreatic bud forms the head, neck, body, and tail - ventral pancreatic bud forms the uncinate process

Question 28

Annular pancreas

Answer 28

ventral bud fails to migrate around the duodenum correctly

Question 29

What can an annular pancreas cause

Answer 29

duodenal stenosis

Question 30

Development of spleen

Answer 30

during the 5th week mesenchyme differentiates to form the spleen - spleen is a MESODERMAL derivative and not an endodermal derivative of the gut tube

Question 31

Distal part of duodenum derived from

Answer 31

midgut

Question 32

Jejunum derived from

Answer 32

midgut

Question 33

ileum derived from

Answer 33

midgut

Question 34

caecum derived from

Answer 34

midgut

Question 35

appendix derived from

Answer 35

midgut

Question 36

ascending colon derived from

Answer 36

midgut

Question 37

promixal 2/3rds of transverse colon derived from

Answer 37

midgut

Question 38

Midgut loop (main events)

Answer 38

Herniation – Physiological umbilical herniation Rotation of midgut loop – 90 degrees counterclockwise in the umbilical cord Retraction of intestinal loops – 180 degrees more counterclockwise rotation Fixation of intestines

Question 39

remnants of the vitalline duct can cause

Answer 39

meckel diverticulum - slight bulge in the small intestine present at birth. May form a vitalline cyst, fistula or ligament

Question 40

What is an omphalocele

Answer 40

herniation of abdominal viscera through an enlarged umbilical ring - may include liver, stomach, intestinal loops. Viscera covered by a layer of amnion

Question 41

What is gastroschisis

Answer 41

Herniation of abdominal contents directly through the body wall into the amniotic cavity - not covered by peritoneum or amnion

Question 42

Distal 1/3rd of transverse colon derived from

Answer 42

hindgut

Question 43

descending colon derived from

Answer 43

hindgut

Question 44

sigmoid colon derived from

Answer 44

hindgut

Question 45

rectum derived from

Answer 45

hindgut

Question 46

upper part of anal canal derived from

Answer 46

hindgut

Question 47

lining of bladder and urethra formed from

Answer 47

endoderm of hindgut

Question 48

What is the cloaca

Answer 48

expanded terminal part of the hindgut and endoderm lined chamber

Question 49

Urorectal fistula

Answer 49

congenital defect in the urorectal septum resulting in passage of urine through the rectum

Question 50

Rectovaginal fistula

Answer 50

abnormal connection between the rectum and the vagina

Question 51

Rectoanal atresia

Answer 51

rare anorectal malformation associating a normal anal canal with a stricture or a complete rectal atresia

Question 52

Imperforate anus

Answer 52

failure of anal membrane to break down