GI Embryo and Histo

Question 1

Digestive tract

extends and consists of

Answer 1

• Long hollow tube
• Extends from esophagus to the rectum
  
  • Includes esophagus, somach, small intestine, large intestine, rectum

Question 2

Digestive tract 4 basic layers

Answer 2

• Mucosa
• Submucosa
• Muscularis externa
• Serosa or Adventita

Question 3

Mucosa 3 components

Answer 3

• Most varied, protect, secrete, absorb
• Epithelium
  
  • Barrier, alters surface area, permits movement of nutrients, water, and electrolytes
• Lamina propia
  
  • LCT that contains glands, vessels for transport, components of immune system
• Muscularis mucosae
  
  • Thin layer of smooth muscle cells in circular and longitudinal arrangement

Question 4

Digestive epithelium 2 types and where are they found

Answer 4

• Stratified squamous epthelium
  
  • Lines oral cavity, pharynx and esophagus
  • Mechanical stresses
• Simple columnar epithelium with mucous cells
  
  • Lines Stomach, small intestine, most of large intestine
  • Absorption

Question 5

Submucosa

Answer 5

• Control of and contribution of mucosal function
  
  • Irregular LCT and DCT, blood and lymph vessels, nerves, glands
    *

Question 6

Muscularis Externa

Answer 6

• Generates peristalsis
• Inner circular smooth muscle
• Connective tissue layer
• Outer longitudinal smooth muscle layer

Question 7

Serosa or Adventitia

Answer 7

• Reduces frictional forces
• Serosa, outermost layer is an overlying epithelial layer
  
  • (esophagus, stomach, SI, part if LI)
• Adventitia, outermost layer adheres to the body wall
  
  • Consists of a CT layer

Question 8

Initial Stomach Rotation

Answer 8

• Liver forces stomach to rotate 90 in a CLOCKWISE fashion
• Stomach is expansion of foregut caudal to the septum transversum
• By month 3–> 180 rotation

Question 9

Further midgut rotation

Answer 9

• Growing ileum elongates faster than abdominal cavity
  
  • Throwing midgut into a hairpin fold called the Primary Intestinal Loop
• Later midgut elongation and pressure resulting from growth of outer abdominal organs (like liver) forces the primary intestinal loop to herniate into the umbilicus
  
  • now a large portion of SI is ouutside body inside the umbilicus

Question 10

Meckels Diverticulum

Answer 10

• Vitelline duct connects embryo midgut to yolk sac and should degenerate at weeks 5 and 8
• 2% of live births have persistent, twice as common in males
• Often seen as a 1-5cm diverticulum from the antimesenteric wall of ileum within 100 cm of cecum
• Vitelline that persist in abdominal wall may form
  
  • Omphalomesenteric fistula
  • Omphalomesenteric Cyst
  • Omphalomesenteric Ligament
  • Connecting SI and umbilicus

Question 11

Pancreas development

Answer 11

• Endodermal thickening
• Fors dorsal and ventral buds
• Branching morphogenesis, endocrine portions differntiate from glandular epithelium