Development of the Digestive System

Question 1

What happens during week 1?

Answer 1

Fertilisation to implantation

Question 2

What happens during week 2?

Answer 2

Bilaminar germ disk formation

Question 3

Which gene is a transcription factor for establishing left sidedness?

Answer 3

PTX2

Question 4

What happens during week 3?

Answer 4

Trilaminar germ disk formation -gastrulation
CNS induction
Neurulation
Makes ectoderm, mesoderm and endoderm

Question 5

What process happens during week 3 to 8?

Answer 5

Organogenesis

Question 6

What structures originate from the embryonic ectoderm?

Answer 6

Skin, CNS, PNS, ear and nose

Question 7

What structures originate from embryonic endoderm?

Answer 7

Epithelial lining of the resp. system, GIT, glands, liver, pancreas, thyroid, urinary bladder

Question 7

What structures originate from embryonic mesoderm?

Answer 7

Muscles, bones, cartilage, dermis, vascular system, urogenital system, spleen

Question 8

When is the gut tube formed?

Answer 8

3rd and 4th week

Question 9

What does lateral plate mesoderm give rise to?

Answer 9

Parietal and visceral mesoderm

Question 10

How is the gut tube closed?

Answer 10

At cranial end by oropharyngeal membrane
At caudal end by cloacal membrane

Question 11

Describe the molecular regulation of the craniocaudal organisation of the gut?

Answer 11

Secretion of sonic hedge hog (SHH) by the gut endothermal cells - creates signalling pathway fir HOX gene

Question 12

What is HOX gene expression do?

Answer 12

In gut mesoderm
Causes craniocaudal organisation of the gut

Question 13

What is the mesentery?

Answer 13

There is ventral and dorsal
Hangs the gut tube from the body wall
Double layers of peritoneum

Question 14

What is the origin of the mesentery?

Answer 14

Mesodermal

Question 15

What does the mesentery enclose?

Answer 15

Intraperitoneal organs

Question 16

Where does the oesophagus develop from?

Answer 16

Cranial part of the gut tube
Foregut
Lung bud develops from ventral wall of the foregut
Tracheo-oesophageal ridge between

Question 17

How is the stomach developed?

Answer 17

Foregut caudal to oesophagus dilates to form stomach
Creates the greater and lesser curvatures

Question 18

Explain the rotations if the stomach when developing

Answer 18

90 degree clockwise around longitudinal axis
Rotation along antero-posterior axis

Question 19

What is the mesogastrium?

Answer 19

The mesentery which attaches the stomach to the dorsal and ventral wall

Question 20

How is the omental bursa behind the stomach formed?

Answer 20

Rotation along the longitudinal axis pulls the dorsal mesentery to the left

Question 21

What does the greater and lesser omentum connect?

Answer 21

Greater - liver and stomach
Lesser - down from stomach along greater curvature to become 4 layers

Question 22

Explain the formation of the duodenum

Answer 22

Formed from caudal part of foregut and cranial part of midgut tube

Question 23

What arteries supply the duodenum?

Answer 23

Coeliac trunk and superior mesenteric artery

Question 24

What are hepatocytes and biliary epithelia formed from?

Answer 24

Endodermal origin

Question 26

What is the origin of kupffer cells, haematopoietic cells and CT?

Answer 26

Mesodermal origin

Question 27

What is the origin of the spleen?

Answer 27

Mesodermal at week 5

Question 28

In spleen, what happens at week 15-17?

Answer 28

Colonised T-lymphocytes

Question 29

In spleen, what happens at week 23?

Answer 29

The B cell precursors arrive and spleen starts its lymphoid function

Question 30

What is the origin of the pancreas?

Answer 30

Endodermal at week 5

Question 31

What happens at week 6 when developing the pancreas?

Answer 31

As duodenum rotates the ventral bud also moves close to dorsal bud Major papilla formed

Question 32

What is the major papilla?

Answer 32

Bile duct and major pancreatic duct

Question 33

What does the midgut contain?

Answer 33

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

Question 34

How is the primary intestinal loop formed?

Answer 34

Anti-clockwise rotation at week 6 Intestine develops in umbilical cord and moves back to abdominal cavity at week 10

Question 35

What is the vitelline duct?

Answer 35

Connects the ilium with yolk sac up to the 12-14th week

Question 36

What does the midgut loop develop into?

Answer 36

Part of duodenum, jejunum, ileum, ascending colon, and 2/3rds of transverse colon

Question 37

When does cecal bud form?

Answer 37

Week 6

Question 38

What are common anomalies in the midgut?

Answer 38

Stenosis, malrotation - reversed rotation

Question 39

Describe omphalocele

Answer 39

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

Question 40

What could be caused from Vitelline duct remaining?

Answer 40

Fistula, cyst,, ligament or Meckel's diverticulum

Question 41

What is formed from hindgut endodermal development?

Answer 41

Distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum and upper part of anal canal

Question 42

What is formed from hindgut ectodermal development?

Answer 42

Lower part of anal canal and anal orifice

Question 43

When does the cloacal membrane rupture?

Answer 43

Week 7

Question 44

What are some developmental anomalies of the hindgut?

Answer 44

Urorectal fistula, rectovaginal and rectoperineal fistula Imperforated anus