Sublingual Salivary glands : Submaxillary Liver Gallbladder Duodenum Ascending colon Cecum Appendix Ileum Parotid salivary gland Pharynx Esophagus Stomach Pancreas Transverse colon Descending colon Jejunum Sigmoid Rectum Functional Sphincters UES LES Pyloric Ileal IAS EAS

Aorta (200) Celiac (700) Portal Vein Superior Mesenteric (700) Inferior Mesenteri c (400) LIVER STOMACH SPLEEN PANCREAS SMALL INTESTINE COLON To Systemic Circulation (1800) mls/min HEPATIC Rates: ml/min

Lymph node Myenteric plexus Submucosal plexus Gland in submucosa Villus Epithelium and Mucosa Muscularis mucosa Submucosa (contains most nerves and bloood vessels) Circular muscle Longitudinal muscle Serosa (connective tissue) Cross-Section of the Alimentary Canal

Epithelial Cell Barrier Microvilli: Brush Border Glycocalyx: Digestive Surface 1. Traps Nutrients 2. Increases Local Viscosity 3. Harbors Enzymes -Protective Barrier, Tight Junctions

- INTRINSIC REGULATION: ENTERIC PLEXI - EXTRINSIC REGULATION: Central Nervous System Autonomic Nervous System Neural Regulation of GI Function

Interganglionic fiber tract Myenteric ganglion Circular muscle Submucosal ganglion 200 um Mucosa Longitudinal Muscle Intrinsic Neural Regulation

The Myenteric Plexus

(-) G (+) to CNS (+) S (-) Protein from CNS Submucosal plexus Pressure receptor Mucosa S H+H+ Signal Integration in the Plexi

Extrinsic Regulation : Primarily Synapses onto Plexi CNS Autonomics Sympathetic (generally inhibits GI function); Norepi Parasympathetic (generally stimulated GI function) Vagus Nerve; Acetylcholine (Ach) Coordinates Functions through Long Reflexes Direct Innervation  f Vascular Smooth Muscle by Sympathetic Nerves: Inhibits Blood Flow Autonomic Nervous System: Regulation of GI Function

Vagal nuclei Sacral Spinal cord Pelvic nerves Vagus nerves Enteric nervous system CNS Preganglionic fibers Postganglionic fibers Myenteric plexus Submucosal plexus Smooth muscle Secretory cells Endocrine (G) cells Blood vessels Parasympathetic division Sympathetic division Sympathetic ganglia Pancreas and Gall Bladder Autonomic Nervous System

Hormone: Classical Definition. A Chemical Messenger Produced and Secreted by a Specialized Gland, and Released into the Blood Where it is Circulated to Distant Organs to Elicit a Physiological Response. - Effects are Exerted Relatively Slowly, but for Prolonged Periods

Aorta (200) Celiac (700) Portal Vein Superior Mesenteric (700) Inferior Mesenteri c (400) LIVER STOMACH SPLEEN PANCREAS SMALL INTESTINE COLON To Systemic Circulation (1800) mls/min HEPATIC Rates: ml/min

TABLE 1. Characteristics of the Major Gastrointestinal Hormones Gastrin G17 peptide (2117 mw) peptides, amino acid secretion, 3 min G34 peptide (3988 mw) acids, distention Gastric growth 12 min Secretin peptide (3056 mw) duodenal acidity pancreatic 3 min bicarbonate secretion CCK-PZ peptide (3919 mw) fatty acids gallbladder contraction amino acids in pancreatic enzyme 5 min the sm. intestine secretion and growth (GIP) peptide (5105 mw) glucose, fatty insulin release 21 min Glucose- dependent acids in the small insulinotropic peptide intestine Local Stimuli Physiologic Circulating Name Composition for Release Action(s) Half-life

Secretin Family: Activates Adenylate Cyclase Secretin Increasing cAMP VIP GIP Glucagon Gastrin Family: Increases Intracellular Ca 2+ Gastrin CCK Receptor Specificity

Blood vessels Lymph vessels Nerves Smooth muscle Connective tissue lymphocytes Plasma cells Eosinophiles Villous epithelium Undifferentiated Goblet Mitoses Endocrine cells Paneth cells Crypt Epithelium Crypt lumen Muscularis mucosa Absorp- tive cells Goblet cells Endocrine cells

Summary of Hormone Distributions

[ Hormone] in Blood Length of Intestine stimulated

Peptide Released by Actions Pancreatic polypeptide Intestinal Inhibits Pancreatic HCO 3 - Protein, Fatand Enzyme Secretion Glucose Motilin ? Distal Gastric Motility Intestinal Motility Enteroglucagon (GLP-1) Intestinal ? Fat, Sugar From, F-cells of pancreatic islets Candidate Hormones

VIP Mucosa and Relaxes Muscle; Smooth Muscle Activates Cl - Channels GRP or Gastric Mucosa Stimulates Gastrin Bombesin Release EnkephalinsNeurons in Mucosa Increases Smooth and Visceral Muscle Muscle Tone Substance P Salivary Glands Activates Blood Flow Neuropeptide Y Neurons in Mucosa Decreases Secretion and Visceral Muscle and Sphincter Tone CCK Enteric and Hypothalamic Inhibits Propulsion Neurons Activates Satiety Peptide Site of Action Actions Neurocrines: NANC Neurotransmitters NANC: Non-Adrenergic Non-Cholinergic

FactorLocation Actions SomatostatinStomach: Decreases Gastrin Pyloric Gland Secretion Histamine* Stomach and Increases Gastric Intestinal Mucosa Acid Secretion Paracrine

Ach GRP Vagus nerves Gastrin Cell Somato- statin Cell Digested Protein H+H+ + Regulation of G-Cell Secretion Myenteric Plexus