Embryology of the GI

Question 1

omphalocele

Answer 1

A new born baby born with herniation of abdominal viscera through an
enlarged umbilical ring

Question 2

how long is the process of fertilisation to implantation in week 1

Answer 2

51/2 to 6 days

Question 3

what occurs during week 2

Answer 3

bilaminar germ disk is formed

Question 4

which gene is a transcription factor for establishing left sidedness

Answer 4

PTX2

Question 5

what occurs during week 3

Answer 5

trilaminar germ disk formation (gastrulation)

Question 6

what 3 processes occur during week 3

Answer 6

gastrulation

CNS induction

Neurulation

Question 7

what three parts make up the trilaminar germ disc

Answer 7

ectoderm
intraembryonic mesoderm
endoderm

Question 8

organogenesis

Answer 8

organ malformation can happen during this period from exposure to any teratogenic substance

Question 9

when can organogesis occur

Answer 9

week 3-8

Question 10

teratogens

Answer 10

drugs
virus
thalidomide (limb deformities)

Question 11

what structures originate from ebryonic ectoderm

Answer 11

Skin (epidermis, hair, nail), CNS,PNS, sensory epithelia of the eye,ear, nose & other structures (pituitary,mammary and sweat glands, enamel of teeth),adrenal medulla etc.

Question 12

what structures originate from embryonic endoderm

Answer 12

Epithelial lining of Respiratory system, GIT, glands, liver (hepatocyte and biliary epithelium), pancreas,
thyroid, parathyroid parenchyma, urinary bladder etc.

Question 13

Embryonic mesoderm

Answer 13

• muscles, bones,cartilage, dermis, vascular system, urogenital system except bladder, spleen, liver
  mesenchyme, adrenal cortex etc.

Question 14

when does the development of the gut tube occur

Answer 14

during the 3rd and 4th week drom the endodermal lining of the yolk sac

Question 15

what gives rise to parietal and visceral mesoderm

Answer 15

lateral plate mesoderm

Question 16

what does parietal layer line

Answer 16

body cavity

Question 17

what does visceral layer line

Answer 17

gut tube

Question 18

what happens to the connection of the gut tube with the yolk sac over time

Answer 18

it becomes smaller until it is only connected at umbilical cord by vitelline duct

Question 19

when does the connection between the gut tube and yolk sac no longer exist

Answer 19

12-14 weeks

Question 20

what is the gut tube closed by at the cranial end

Answer 20

oropharyngeal membrane

Question 21

what is the gut tube closed by at the caudal end

Answer 21

cloacal membrane

Question 22

sonic hedgehog signalling pathway

Answer 22

secretion of SHH by gut stimulates expression of HOX gene

craniocaudal organisation of gut
Instructs what it should become - eg small intestine, large intestine or cloaca

Question 23

mesentery

Answer 23

ventral and dorsal

double layers of peritoneum

hangs the gut tube from body wall

encloses organs (intraperitoneal)

Question 24

what does the foregut include

Answer 24

extends from lung bud diverticulum to bile duct opening of the duodenum, consists of pharync oesophagus stomach and perennial part of duodenum

Question 25

what does the oesophagus develop from

Answer 25

cranial part of the gut tube

Question 26

where does the lung bud develop from

Answer 26

ventral wall of the foregut 4 weeks

Question 27

Tracheo- oesophageal septum (ridge)

Answer 27

The formation of a tracheoesophageal septum will divide the ventral trachea from the dorsal esophagus. Failure to separate will result in tracheoesophageal fistula

Question 28

what forms the stomach

Answer 28

foregut dilates to form the stomach week 4 creates lesser and greater curvatures

Question 29

what is the longitudinal rotation of the stomach

Answer 29

90 degrees rotation

Question 30

what is the second rotation of the stomach

Answer 30

Rotation along antero-posterior axis

Question 31

how is the stomach attached to both the ventral and dorsal wall

Answer 31

a mesentery called mesogastrium

Question 32

what does rotation along the longitudinal axis do to the mesentery

Answer 32

pulls the dorsal mesentery to the left creates omental bursa behind the stomach (lesser sac)

Question 33

what is the duodenum formed from

Answer 33

caudal part of the foregut and the cranial part of the midgut tube

Question 34

blood supply of duodenum

Answer 34

Both coeliac trunk and superior mesenteric artery

Question 35

retroperitoneal and duodenum

Answer 35

anatomical space (sometimes a potential space) behind (retro) the peritoneum duodenum is retroperitoneal except from the duodenal cap

Question 36

what week of gestation is the liver bud formed

Answer 36

week 3

Question 37

hepatocytes, biliary epithelia

Answer 37

endodermal in origin

Question 38

Kupffer cells, haematopoietic cells and connective tissue

Answer 38

mesodermal origin (septum transversum)

Question 39

Falciform ligament and lesser omentum

Answer 39

develops from ventral mesentery

Question 40

Gall bladder and cystic duct

Answer 40

(endodermal origin)

Question 41

what week of gestation does bile form

Answer 41

12th week

Question 42

spleen

Answer 42

mesodermal origin week 5

Question 43

spleen in Weeks 15 to 17

Answer 43

colonised by T lymphocytes

Question 44

spleen in week 23

Answer 44

the B-cell precursors arrive and spleen starts it’s lymphoid function

Question 45

pancreas

Answer 45

endodermal in origin (wk-5)

Question 46

what happens as the duodenum rotates

Answer 46

the ventral bud also moves close to the dorsal bud (wk-6)

Question 47

(bile duct and major pancreatic duct)

Answer 47

Major papilla

Question 48

Incomplete separation of lung bud

Answer 48

oesophageal atresia and tracheo-oesophageal fistula

Question 49

what are some development abnormalities of the foregut?

Answer 49

Obliterated bile duct, distended hepatic duct Duplication of gall bladder Accessory pancreatic duct

Question 50

where does the midgut extend to and from?

Answer 50

from opening of bile duct into the duodenum to proximal 2/3rds of the transverse colon

Question 51

describe the formation of the primary intestinal loop?

Answer 51

Anti-clockwise rotation Physiological herniation of intestinal loop (Wk-6) Vitelline duct connects the ilium with yolk sac (up to 12th-14th wk) Intestinal loops begin to move back into the abdominal cavity (wk-10)

Question 52

what develops around week 6 during formation of primary intestinal loop?

Answer 52

cecal bud develops

Question 53

what occurs after Intestinal loops begin to move back into the abdominal cavity (wk-10)

Answer 53

The midgut loop elongates and will differentiate into part of the duodenum, jejunum, ileum, ascending colon, and two- thirds of the transverse colon

Question 54

what are common developmental abnormalities of the midgut?

Answer 54

Common anomalies: stenosis, malrotation etc.

Question 55

omphalocele

Answer 55

Failure of retraction of herniated intestinal loop through umbilical ring at week-10

Question 56

what happens when the vetelline duct persists

Answer 56

In 2-4% people a small vitelline duct persists May form fistula/cyst / ligament/Meckel's dive

Question 57

describe the development of the hindgut

Answer 57

Endodrmal origin: Distal 1/3rd transverse colon, descending colon, sigmoid colon, rectum and upper part of the anal canal. *Ectodermal origin: Lower part of the anal canal and anal orifice

Question 58

what is the origin of the cranial part of the anal canal

Answer 58

endodermal

Question 59

what is the origin of the caudal part of the anal canal

Answer 59

ectodermal

Question 60

what happens to the cloacal membrane at week 7 gestation

Answer 60

it ruptures

Question 61

what are the developmental abnormalities of the hindgutt?

Answer 61

urorectal fistula rectovaginal fistual rectoperineal fistula imperforate anus