Hy Embryology 07

Front 1

Describe the formation of the primitive gut tube

Back 1

The primitive gut tube is formed form the incorporation of the dorsal part of the yolk sac into the embryo due to the craniocaudal folding and lateral folding of the embryo

Front 2

Describe the location and divisions of the primitive gut tube

Back 2

1. Extends from the oropharyngeal membrane to the cloacal membrane

2. Divided into the foregut, midgut, and hindgut

Front 3

Describe the changes in the primitive gut tube as development occurs

Back 3

Early in development, the epithelial lining the gut tube proliferates rapidly and obliterates the lumen

Later, recanalization occurs

Front 4

What are the derivatives of the foregut?

Back 4

-Esophagus
-Stomach
-Liver
-Gallbladder
-Pancreas
-Upper duodenum

Front 5

What are the derivatives of the midgut?

Back 5

-Lower duodenum
-Jejunum
-Ileum
-Cecum
-Appendix
-Ascending colon
-Proximal 2/3 of the transverse colon

Front 6

What are the derivatives of the hindgut?

Back 6

-Distal third of the transverse colon
-Descending colon
-Sigmoid colon
-Rectum
-Upper anal canal

Front 7

What artery supplies the derivatives of the foregut?

Back 7

Celiac artery

Front 8

Describe the formation of the esophagus

Back 8

1. The foregut is divided into the esophagus dorsally and the trachea ventrally by the tracheoesophageal folds, which fuse to form the trachcoesopageal septum

Front 9

Describe esophageal atresia

Back 9

1. Occurs when the traceoesophageal septum deviates too far dorsally, causing the esophagus to end as a closed tube

2. About 33% of patients with esophageal atresia also have other congenital defects associated with the VATER or VACTERL syndrome

3. It is associated clinically with polyhydramnios and a tracheoesophagea fistula

Front 10

Describe esophageal steonosis

Back 10

1. Occurs when the lumen of the esophagus is narrowed and usually involves the midesophagus

2. The stenosis may be caused by submucosal/muscularis externa hypertrophy, remnants of the tracheal cartilaginous ring within the wall of the esophagus, or a membranous diaphragm obstructing the lumen probably due to incomplete recanalization

Front 11

Describe the causes of esophageal stenosis

Back 11

The stenosis may be caused by submucosal/muscularis externa hypertrophy, remnants of the tracheal cartilaginous ring within the wall of the esophagus, or a membranous diaphragm obstructing the lumen probably due to incomplete recanalization

Front 12

Describe achalasia

Back 12

1. Occurs due to the loss of ganglion cells in the myenteric (Auerbach) plexus and is characterized by the failure to relax the lower esophageal sphincter

2. This will cause progressive dysphagia and difficulty swallowing

Front 13

Describe the formation of the primitive stomach

Back 13

A fusiform dilatation forms in the foregut in week 4, which gives rise to the primitive stomach

Front 14

Describe the formation of the stomach

Back 14

1. The primitive stomach rotates 90 degrees clockwise around its longitudinal axis

2. As a result of this clockwise rotation, the dorsal mesentery is carried to the left and eventually forms the greater omentum

3. The left vagus nerves innervates the ventral surface of the stomach

4. The right vagus nerve innervates the dorsal surface of the stomach

Front 15

Describe the innervation of the stomach

Back 15

1. The left vagus nerve innervates the ventral surface of the stomach

2. The right vagus nerve innervates the dorsal surface of the stomach

Front 16

Describe hypertrophic pyloric stenosis

Back 16

1. Occurs when the muscularis externa in the pyloric region hypertrophies, causing a narrow pyloric lumen that obstructs food passage

2. It is associated clinically with projectile, nonbilious vomiting after feeding and a small, palpable mass at the right costal margin

3. Increased incidence has been found in infants treated with the antibiotic erythromycin

Front 17

What antibiotic is associated with hypertrophic pyloric stenosis?

Back 17

Erythromycin

Front 18

Describe the treatment of hypertrophic pyloric stenosis

Back 18

Involves surgical incision of the hypertrophic muscle

Front 19

Describe the formation of the liver

Back 19

1. The endodermal lining of the foregut forms an outgrowth (called the hepatic diverticulum) into the surrounding mesoderm of the septum transversum

2. Cord of hepatoblasts (called hepatic cords) from the hepatic diverticulum grow into the mesoderm of the septum transversum

3. The hepatic cords arrange themselves around the vitelline veins and umbilical veins, which course through the septum transversum and form hepatic sinusoids

4. The liver bulges into the abdominal cavity, thereby stretching the septum transversum to form the ventral mesentery, consisting of the falciform ligament and the lesser omentum

Front 20

What are the components of the ventral mesentery?

Back 20

Falciform ligament and the lesser omentum

Front 21

Describe the falciform ligament

Back 21

1. Contains the left umbilical vein

2. Left umbilical vein regresses after birth to form the ligamentum teres

Front 22

Describe the lesser omentum

Back 22

1. Can be divided into the hepatogastric ligament and the hepatoduodenal ligament

2. The hepatoduodenal ligament contains the bile duct, portal vein, and hepatic artery (ie, portal triad)

Front 23

Describe congenital malformation of the liver

Back 23

Rare

Front 24

Describe the formation of the gallbladder

Back 24

1. The connection between the hepatic diverticulum and the foregut narrows to form the bile duct

2. An outgrowth from the bile duct gives rise to the gallbladder rudiment and cystic duct

Front 25

Describe intrahepatic gall bladder

Back 25

Occurs when the gallbladder rudiment advances beyond the hepatic diverticulum and becomes buries within the substance of the liver

Front 26

Describe floating gall bladder

Back 26

1. Occurs when the gallbladder rudiment lags behind the hepatic diverticulum and thereby becomes suspended from the liver by a mesentery.

2. A floating gall bladder is at risk for torsion

Front 27

Describe developmental anomalies of the cystic duct

Back 27

Fairly common

Front 28

Describe developmental anomalies of the gallbladder anatomy

Back 28

Fairly common in which two, bilobed, diverticula, and septated gallbladders are found

Front 29

Describe biliary atresia

Back 29

1. The obliteration of extrahepatic and/or intrahepatic ducts

2. The ducts are replaced by fibrotic tissue die to acute and chronic inflammation

3. Clinical findings include progressive neonatal jaundice with onset soon after birth, white, clay-colored stool, and dark-colored urine

4. Average survival time is 12-19 months with a 100% mortalitiy rate

Front 30

Describe the clinical findings of biliary atresia

Back 30

-Progressive neonatal jaundice with onset soon after birth
-White, clay-colored stool
-Dark colored urine