Development Of The GI Tract

Question 0

What does cephalocaudal folding create?

Answer 0

Cranial and caudal pockets from the yolk sac endoderm (beginning primitive gut development)

Question 1

What does lateral folding of the embryo create?

Answer 1

The ventral body wall Primitive gut becomes tubular

Question 2

Structure of the primitive gut at the very earliest stage? (PICTURE)

Answer 2

A blind-ended tube of the foregut and the hindgut Midgut remains connected with the yolk sac

Question 3

In which week does the primitive gut tube begin developing and how?

Answer 3

3rd week Pinches off from yolk sac cavity

Question 4

Where does the primitive gut tube run from and to?

Answer 4

Stomatodeum (future mouth) to proctodeum (future anus) Has an opening for the umbilicus

Question 5

Where is the epithelial lining of the future gut derived from?

Answer 5

Endoderm

Question 6

Where is the external lining of the gut tube derived from?

Answer 6

Splanchnic mesoderm

Question 7

What is the external lining of the gut tube composed of?

Answer 7

Musculature and visceral peritoneum

Question 8

What is the midgut connected to the yolk sac by?

Answer 8

Vitelline duct

Question 9

Where is the gut tube suspended and by what?

Answer 9

Suspended in the intraembryonic coelom by a double layer of splanchnic mesoderm

Question 10

Adult derivatives of the foregut?

Answer 10

Oesophagus, stomach, pancreas, liver, gall bladder, duodenum (proximal to entrance of the bile duct)

Question 11

What are the adult derivatives of the midgut?

Answer 11

Duodenum (distal to entrance of the bile duct), jejunum, ileum, cecum, ascending colon, proximal two thirds transverse colon

Question 12

Adult derivatives of the hind gut?

Answer 12

Distal third of transverse colon, descending colon, sigmoid colon, rectum, upper anal canal, internal lining of bladder and urethra

Question 13

Blood supply to each part of the primitive gut tube?

Answer 13

Foregut - celiac trunk Midgut - superior mesentric artery Hindgut - inferior mesentric artery

Question 14

Which structures have a mixed blood supply?

Answer 14

Those that develop close to the junction between foregut and midgut Such as -the duodenum - proximal to entry of bile duct is celiac trunk, distally is SMA -pancreas - head supplied by celiac trunk and SMA

Question 15

What is the intraembryonic coelom (cavity) divided by and into what?

Answer 15

Divided by the diaphragm into abdominal and thoracic cavities

Question 16

What is the serous membrane in the abdominal and thoracic cavity?

Answer 16

Abdominal - peritoneal membrane Thoracic - pleural membrane

Question 17

What is a mesentery?

Answer 17

Double layer of peritoneum suspending the gut tube from the abdominal wall

Question 18

What do the mesenteries allow?

Answer 18

Conduit for blood and nerve supply Mobility where needed

Question 19

What surrounds the gut tube when suspended in the intraembryonic cavity?

Answer 19

Splanchnic mesoderm

Question 20

What mesoderm is the mesentery of the gut tube derived from?

Answer 20

Splanchnic mesoderm

Question 21

Which sections of the gut are dorsal and ventral mesenteries found?

Answer 21

Dorsal - along the whole gut tube Ventral - only in the region of the foregut so this part is tethered on both sides

Question 22

What do dorsal and ventral mesenteries of the foregut do?

Answer 22

Divide the cavity into left and right sacs -left sac contributes to the greater sac -right sac becomes the lesser sac which comes to lie behind the stomach

Question 23

What is the greater omentum formed from?

Answer 23

The dorsal mesentery

Question 24

What is the lesser omentum derived from?

Answer 24

The ventral mesentery

Question 25

What does rotation of the stomach create?

Answer 25

The greater and lesser sacs and omenta

Question 26

In which direction is rotation of the stomach?

Answer 26

Longitudinal axis Anteroposterior axis

Question 27

What happens as a result of rotation of the stomach?

Answer 27

Puts vagus nerves anterior and posterior to the stomach (instead of on left and right) Shifts cardia and pylorus from the midline Contributes to moving the lesser sac to behind the stomach Creates the greater omentum

Question 28

What is a peritoneal reflection?

Answer 28

Change of direction from parietal peritoneum to mesentery, from mesentery to visceral peritoneum, etc.

Question 29

What does it mean if an organ is secondarily peritoneal?

Answer 29

Began development invested by peritoneum and had a mesentery With successive growth and development, the mesentery is lost through fusion with posterior abdominal wall

Question 30

How do the oesophagus and respiratory primordium develop?

Answer 30

A respiratory diverticulum develops in the 4th week in the ventral wall of the foregut at the junction with the pharyngeal gut Get the respiratory primordium ventrally and the oesophagus dorsally A tracheoesophageal septum develops to separate them

Question 31

What is a tracheoesophageal fistula caused by and what is it?

Answer 31

Posterior deviation of the t/o septum Mechanical pressure on foregut dorsal wall pushing it anteriorly Proximal part of the oesophagus ends as a blind sac Distal part is connected to the trachea by a narrow canal just above the bifurcation

Question 32

What creates the greater curvature?

Answer 32

Faster growth of the dorsal border of the stomach primordium

Question 33

What are some foregut-derived glands formed in the ventral mesentery?

Answer 33

Liver Biliary system Uncinate process and inferior head of pancreas

Question 34

What foregut-derived glands are derived in the dorsal mesentery?

Answer 34

Superior head, neck, body and tail of the pancreas

Question 35

What does the liver develop from and when does it appear?

Answer 35

A hepatic bud within the ventral mesentery which appears on the third week

Question 36

Where does the hepatic bud appear?

Answer 36

Endodermal epithelium at distal end of foregut

Question 37

When is the liver fully developed?

Answer 37

By week 6

Question 38

What is the bare area of the liver?

Answer 38

Where there is no peritoneal covering Shows the close association of the liver to the diaphragm

Question 39

Describe the development of the duodenum

Answer 39

Develops from the caudal foregut and cranial midgut Grows rapidly to form a C-shaped loop which stomach rotates In 5th and 6th weeks, lumen is obliterated and then recanalised Stomach rotation pushes the duodenum right, then against the posterior abdominal wall

Question 40

What can cause oesophageal atresia?

Answer 40

Displacement of the tracheo-oesophageal septum Ischaemia caused by a vascular accident Recanalisation failure

Question 41

What is a sign during pregnancy that there is oesophageal atresia?

Answer 41

Polyhydraminos -accumulation of amniotic fluid because the foetus has an upper GI tract obstruction, therefore normal swallowing of amniotic fluid is not possible.