Development of the Digestive System

Question 1

What is the name of the tube formed from the curvature of the embryo with the endoermal lining of the yolk sac?

what is the major feature that is different from a fully developed fetus?

Answer 1

primitive gut

it is sealed at both ends

Question 2

What closes the primitive gut on the caudal end?

cranial end?

What is the name of the depression surrounding each of these structures

Answer 2

cloacal membrane (proctodium)

oralpharyngeal membrane (stomodium)

Question 3

Which arteries primarily supply the foregut, midgut, and hindgut?

Answer 3

foregut: celiac artery
midgut: superior mesenteric artery

inferior mesenteric artery: hindgut

Question 4

What surrounds the endodermal lining of the primitive gut?

What structure forms the mesentary?

Answer 4

splanchnic mesoderm

mesoderm also suspends he primitive gut from the body wall as mesentery

Question 5

What 3 structures come from the transverse septum?

Answer 5

liver, ventral mesentery, and diaphragm

Question 6

Identify the indicated features of the fetus

Answer 6

Question 7

Identify the sections of the dorsal mesentery

Answer 7

Question 8

The ventral mesentary always moves with which organ?

Answer 8

liver

Question 9

How does the relationship between the stomach and the vagus nerves shift through development?

Answer 9

initially, the vagus nerves are lateral to the stomach, but as the stomach shifts from a cranial/caudal perspective to a more horizonal position, the vagus nerves shift to dosal and ventral to the stomach

Question 10

What are the 3 phases to the development of the stomach?

What are the major effects of this rearrangement?

Answer 10

1. localized dilation of the foregut
2. rotation in transverse plane (anterior rotates over)
3. rotaion in frontal plane (piloric end moves supriorly and to the right

rearranges the 2 mesentary

dorsal: omental bursa (greater omentum)
ventral: lesser omentum (Hepatoduodenal Ligament)

Question 11

What impact does the rotation of the stomach have on the shape of the duodemum

The duodenum marks the beginning of what strucuture?

Answer 11

The rotation fo the stomach, combine with lesser rotation of the duodenum, produces the C-shape of the duodenum adn displaces the duodenum to the right and dorsad

small intestine (boundary between foregut and midgut)

Question 12

Why is the liver considered a composite organ?

Answer 12

it is made up of endodermal cells from the proximal duodenal wall (by way of hepatic diverticulum) that invades and combines with mesodermal cells from the septum transversum

Question 13

identify the aspects of the ventral messentary that are segmented by the expansion of the liver

Answer 13

Expansion fothe liver subdivides the ventral mesentary into Falciform Ligament, Lesser Omentum, and Hepatogastric Ligament

Where the liver abuts the diaphragm you get a “bare area”

Question 14

Identify the indicated features of the developing pancreas

Answer 14

The major papilla forms from the (rotated) ventral bud; the ventral bud and hepatic deiverticulum form the main pancreatic duct, which also drains most of the dorsal bud

Question 15

What is different about the spleen development as compared to other abdominal organs?

Answer 15

it has not adult or embryonic connection to the primitive gut

develops as a mesodermal proliferation in the dorsal mesentery that is secondarily invaded by vscular tissue

Question 16

What are the 3 major steps in development of the midgut?

Answer 16

1. Formation of Primary Intestinal Loop (PIL)
2. PIL rotates 90 degrees adn pushes into hte umbilical cord (physiloogicla Herniation) – week 6
3. PIL elongates (especially cephalic) and is retracted into the body cavity… durign the retraction the PIL rotates another 180 degrees … week 10

Question 17

What makes up the cephalic limb?

The Caudal limb?

Answer 17

• cephalic limb:
  
  • duodenum
  • ileum
• Caudal Limb
  
  • distal ileum
  • transverse colon

axis of rotation is the vitelline duct (yolk sac) and superior mesenteric artery

Question 18

What part of the midgut retracts frist? How is its movement different?

Answer 18

the jejunum retracts frist and moves to the left side

the rest of the small intestine retracts to the right

last to retract is the cecal bud, which moves to the upper right quadrant; cecum will descend to the lower right as the appendix develops

Question 19

List the portions of the digestive system that fall into the following categories:

Retroperitoneal viscera

secondarily retroperitoneal viscera

Answer 19

• Reroperitoneal viscera
  
  • Esophagus
  • Rectum
• secondarily retroperitoneal viscera (loses dorsal mesentary)
  
  • pancreas
  • most of duodedenum
  • ascending and descending colon

Question 20

What structure separates the cloaca into a ventral urinary chamber and a dorsal digestive chamber?

Answer 20

urorectal septum

Question 21

What is difference about the most distal part of the anal/rectal junction and the deeper portion?

What is the name of the line of fusion?

Answer 21

distal: from surface of body (inferior rectal arteries)
deeper: digestive tract (superior rectal arteries)

pectinate line

Question 22

Where do the arteries that supply the pancreas come from?

Answer 22

Inferior anterior and posterior pancreaticoduodenal aa come off of the superior mesenteric artery

supeior anterior and posterior pancreaticoduodenal aa come off the gastroduodenal, off of the common hepatic, from the celiac trunk

Question 23

What is the name of the process where the epithelial rod breaks down to produces a lumen?

What happens when this process fails?

Answer 23

recanilization

failure of recanilzation leads to stenosis

Question 24

What is the cause of pyloric stenosis?

What symptom could indicate this problem?

Answer 24

excessive smooth muscles at the pyloric sphincter

infants prsent with projectile vomitting

Question 25

What can happen if the bile duct does not canalize?

Answer 25

bile cannot reach the duodenum

infant is born with jaundice; fatal without surgical intervention

Question 26

What is the name for abnormal migration of the ventral pancreatic duct that leaves a ring of pancreatic tissue around the duodenum?

What can happen?

Answer 26

Annular Pancreas

possible constriction/obstruction of the duodenum

Question 27

What is the name of the following conditions?

1. abnormal rotation of the midgut. Can result in a constriction or obstructin of the gut itself, or occlusion of the superior mesenteric artery
2. only partial rotation occurs, caudal limb retracts first instead of cephalic limb
3. PIL rotates clockwise instead of counter-clockwise. Transverse colon shofts relative to duodenum and superior mesenteric artery and may be constricted

Answer 27

1. Volvulus
2. Left-sided colon
3. Reversed midgut rotation

Question 28

What does not develop in Hirschsprung Disease?

Answer 28

The ganglion of the autonoic system do not develop, so peristaltic contractiosn do not occur

so, get congenital megacolon