GI Tract

Question 1

Upper GI tract

Answer 1

Mouth –> esophagus –> stomach –> Ligament of Treitz (duodenum)

Question 2

Lower GI tract

Answer 2

Rest of duodenum –> jejunum –> ileum –> large intestine (appendix) –> rectum –> anus

Question 3

Layers of GI Tract Wall (Innermost–>Outermost)

Answer 3

1. Mucosa
2. Submucosa
3. Muscularis Propia

Question 4

Mucosa layers (innermost–>outermost)

Answer 4

1. Epithelium: inner cell lining; in contact w/ lumenal contents
2. Lamina Propria
3. Muscularis mucosa: smooth muscle layer

Question 5

Submucosa layer

Answer 5

Submucosal plexus - controls glandular secretion, motility, digestion
Contains glands

Question 6

Muscularis propia

Answer 6

Main smooth muscle layer - affects peristalsis (motility) + segmentation (mixing)
Contains myenteric plexus - controls glandular secretion, motility, digestion

Question 7

Peristalsis

Answer 7

Movement of food through different portions of GI tract

Question 8

Segmentation

Answer 8

Mixing of food between one GI tract segment & another

Question 9

Enteric NS/Intrinsic NS of Digestive System

Answer 9

= Submucosal plexus + myenteric plexus
Fxn: digestion, motility, ctrl glandular secretion
Independent control of motility + glandular secretion w/o consulting brain
Susceptible to ANS input
-PNS –> stim ENS
-SNS –> inhibit ENS

Question 10

Esophagus epithelium

Answer 10

Non-keratinized stratified squamous

-Stratified: multiple layers = protective barrier against food

Question 11

Stomach epithelium

Answer 11

Simple columnar w/ goblet cells

• Goblet cells secrete mucus - protect stomach lining from acid
• Fxns: mixing, acid secretion, pepsinogen activation into pepsin (protease enzyme); absorbs alc + NSAIDs

Question 12

Small intestine epithelium

Answer 12

Mucosa arranged into villi (epithelial fingerlike projections) - increase SA for absorption
Simple columnar epithelium w/ microvilli - one layer of cells = efficient absorption; microvilli = projections on single cells - increase SA and contain brush border enzymes (degradation of stuff into simple components) for absorption

Question 13

Large intestine epithelium

Answer 13

• Flatter mucosa
• Simple columnar epithelium
  
  • H2O Reabsorption into stool
  • No nutrient absorption

Question 14

Parietal cells

Answer 14

Stomach secretory cells that release H+ and intrinsic factor

Question 15

ECL cells

Answer 15

Stomach secretory cells that release histamine

Question 16

Gastrin + Histamine

Answer 16

Local hormones that stimulate parietal cell H+ release

Question 17

Chief cells

Answer 17

Stomach secretory cell that secretes pepsinogen (later cleaved into pepsin via acid; pepsin = protease)

Question 18

Mucus cells

Answer 18

Stomach secretory cells that release mucus (protects stomach lining from acid)

Question 19

G cells

Answer 19

Stomach secretory cell that releases gastrin

Question 20

Mucosal barrier of stomach

Answer 20

• Protects stomach lining from acid

- Contains HCO3- (neutralizes acid)

Question 21

Prostaglandins

Answer 21

Protect stomach lining via inhibition of H+ secretion, promoting HCO3- secretion, and promoting good blood flow to stomach for epithelial regeneration