Digestion Stomach Mucosa Chemical Digestion Control of Digestion

Digestion Stomach Mucosa Chemical Digestion Control of Digestion SI Anatomy Marieb 23

Controlling Gastric Juice Levels 1. Cephalic 2. Gastric 3. Intestinal

Phase 1: Cephalic or Reflex Phase 1”-5” before food enters stomach Small gastric acid release + Taste, thought of food - Low appetite, depression, Ghrelin

Phase 2: Gastric ENS, G Cells 3 -4’, 2/3 of Gastric acid + Proteins Increase p. H Distension - Too low p. H

Proteins Change p. H

Phase 3: Intestinal Phase (Mostly Inhibitory) Too much acid, protein, fats Gastrin Inhibitors CCK Secretin

Phase 3: Intestinal Phase (Mostly Inhibitory) Distention of SI Pyloric sphincter closes

Mechanical Digestion and Distension Cyclic Slow Waves: 3/minute Stronger with distension Stronger as you move distally through stomach

Pyloric Region: The Stomach’s Blender Pyloric antrum Stomach 30 ml SI SI 27 ml Stomach Net 3 ml/contraction

The SI is the Main Digestive Organ 1” in diameter 6 -7 m in cadaver 2 -4 m in living person Chemical Digestion Absorption

Small Intestine: Gross Anatomy Pyloric sphincter Duodenum*** Jejunum Illeum Ileocecal Valve

Small Intestine is Specialized for Absorption Mucosa has a huge surface area Plicae circulars (1 cm)

Villi in the Small Intestine Villus (1 mm) Capillary bed Lacteal Intestinal Crypts