Digestive Development (Embryo)

Question 1

How is the gut formed?

Answer 1

Foregut, midgut and hindgut from portion of the yolk sac
Endodermal epithelium
Splanchnic mesoderm for CT and muscle

Question 2

What is the only part of the digestive system not formed from endoderm?

Answer 2

Anal canal which is ectodermal

Question 3

What structures are in the foregut?

Answer 3

Esophagus, stomach, descending duodenum (liver, pancreas)
Innervated by celiac artery

Question 4

What structures are in the midgut?

Answer 4

Ascending duodenum, jejunum, cecum, colon, ascending part of the transverse colon
Innervated by cranial mesenteric artery

Question 5

What structures are in the hindgut?

Answer 5

Part of the transverse colon, cloaca (rectum)
Innervated by caudal mesenteric artery

Question 6

Development of the esophagus

Answer 6

Major growth is longitudinal growth in neck and thorax
Failure to grow = mal-positioning of the stomach

Question 7

Development of the stomach

Answer 7

Dorsal enlargement undergoes 90 degree rotation that brings the dorsal part of the stomach to the left and ventral part close to liver

Question 8

@ birth the _________ is 3-4 times bigger than the rumen?

Answer 8

Abomasum (enzymes needed for milk from mother)

Question 9

Physiological atresia

Answer 9

Early embryo entire gut is occluded
Temporary and re-canalization begins by the end of the embryonic stage

Question 10

Physiological herniation of the gut

Answer 10

Early embryo, midgut grows faster in length and can’t be accommodated in abdominal cavity –> herniates into extraembryonic coelom of the umbilical cord –> herniated loop undergoes 360 degree rotation

Question 11

What is the axis of the herniated loop?

Answer 11

Cranial mesenteric artery

Question 12

Ascending colon on the pig and ox

Answer 12

Coiled in ox
Spiral in pig

Question 13

Ascending colon of the horse

Answer 13

Folds upon itself to form pelvic, sternal and diaphragmatic flexures

Question 14

Development of the rectum

Answer 14

Partitioning of the cloaca by urorectal septum that separates the rectum from the urogenital sinus

Question 15

Cloaca

Answer 15

Common opening for the digestive, urinary and genital systems

Question 16

Development of the anal canal

Answer 16

In-growth of the skin ectoderm (proctoderm) that meets with the rectal endoderm forming the cloacal membrane –> cloacal membrane ruptures and rectum and anal canal continuous

Question 17

What forms the anal sacs in carnivores?

Answer 17

2 lateral outpouchings of the ectoderm and associated glands

Question 18

Abnormalities of anal canal development

Answer 18

Anal canal atresia, rectal atresia (failure to canalize)
imperforate anus

Question 19

Development of sinusoids (liver)

Answer 19

Umbilical and vitelline veins passing through liver

Question 20

Development of hepatic cords (liver)

Answer 20

Ventral hepatic diverticulum (endodermal)
Hepatic diverticulum branches, terminal branches become bile canaliculi (drain bile from hepatocytes to bile duct)

Question 21

Development of the pancreas

Answer 21

Develops as dorsal and ventral endodermal primordia of the duodenum

Question 22

Dorsal primordia

Answer 22

Grows into greater omentum
Bulk of left pancreatic lobe derived

Question 23

Ventral primordia

Answer 23

Forms most of the right pancreatic lobe

Question 24

Openings int he pancreatic duct system

Answer 24

Pancreatic duct (opens in conjunction with bile duct)
Accessory pancreatic duct (opens caudal to bile duct)

Question 25

Achalasia

Answer 25

Continual constriction of esophageal musculature
Usually do to neuromuscular defect
Common in carnivores
Symptoms: vomiting after eating solid food

Question 26

Mal-positioning of the stomach

Answer 26

Failure to descend, rotate or rotate on the right side instead of the left

Question 27

Atresia of intestine

Answer 27

Closure of digestive tube usually due to a failure of the gut to recanalize

Question 28

Umbilical Hernia

Answer 28

Results from incomplete closure of the umbilical ring

Question 29

Persistent Meckel’s diverticulum

Answer 29

Ileal fistula/ vitelline fistula or cyst of sinus
Failure of yolk sac remnant to atrophy