Development of GI Flashcards
What germ layer is the epithelium derived from, and what are the exceptions?
Endoderm
Except the Mouth and Anal canal
What germ layer is the mesenchyme layer derived from?
Splanchnic mesoderm
Also makes the smooth muscle and connective tissue
What tissue are derived from Neural Crest Cells?
The autonomic ganglia
What germ layer are the mouth and anal canal derived from?
Ectoderm
What are the divisions of the GI tract and what structure determines this layout?
Foregut
Midgut
Hindgut
Determined by where the Yolk sac attaches.
Above Yolk sac = Foregut
At Yolk Sac = Midgut
Below Yolk sac = Hindgut
What structures are part of the Foregut?
Pharynx Respiratory System Esophagus Stomach Liver Pancreas Biliary Apparatus Proximal Duodenum
What structures are part of the Midgut?
Small intestine Cecum Appendix Ascending Colon Right Half of Transverse Colon
What structures are part of the Hindgut?
Left Half of Transverse Colon Descending Colon Sigmoid Colon Rectum Superior Anal Canal Epithelium of Urinary Bladder/Urethra
What structure separates the Foregut and Midgut?
The Major Duodenal Papilla (the opening in the 2nd part of the duodenum where the common bile duct and pancreatic duct meet the intestine)
What are the 3 blood vessels that supply blood to the 3 divisions of the GI tract respectively?
Celiac Trunk supplies the Foregut
Superior Mesenteric A. supplies the Midgut
Inferior Mesenteric A. supplies the Hindgut
What germ layer derives the Mucosa of the Esophagus?
Foregut endoderm
What’s special about the esophageal mesenchyme and what germ layers cause this?
Esophagus has skeletal and smooth muscle
Skeletal primarily in the superior portion
Smooth primarily in the inferior portion
Smooth Muscle is derived from Splanchnic Mesoderm
Skeletal Muscle is derived from Pharyngeal Arch Mesoderm (specifically arch 4 and 6)
What is a tracheal esophageal fistula?
An abnormal passage between the trachea and the esophagus (due to an failure of tracheoesophageal folds to properly form the tracheoesophageal septum; occurs in week 5)
Presenting signs and symptoms:
- Prenatally: Polyhydramnios (too much amniotic fluid)
- Birth: Coughing, gagging, cyanosis, vomiting, voluminous oral secretions, possible respiratory distress
What is Esophageal Atresia?
Blind end esophagus
When does the stomach begin to form?
4th week
How does the stomach form?
Starts as a swelling inferior to esophagus
Ventral side grows at a faster rate forming a pocket
Pocket rotates in transverse plane 90 degrees so that ventral pocket is facing left
Then it rotates in the coronal plane 90 degrees so that the greater curvature is below and the lesser curvature is above
What happens to the vagus nerves as the stomach rotations occur?
The Left vagus nerve becomes anterior while the Right Vagus nerve becomes posterior (clockwise rotation)
What is Hypertrophic Pyloric Stenosis?
Circular and some longitudinal muscles of the Pylorus become hypertrophied, constricted the Pylorus
Patient projectile vomits soon after eating, has smaller and fewer stools, failure to gain weight or may lose weight
Cause unknown; very common
What structure are formed from the hepatic diverticulum?
The liver, biliary system, and the ventral pancreatic bud
As the liver grows superiorly, it fuses with what structure?
Septum transversum (diaphragm)
When does bile production begin?
12th week
When does hematopoiesis in the liver begin?
Week 6-30