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Parotid salivary gland Salivary glands: Sublingual Submaxillary Functional Sphincters Pharynx • UES Esophagus Liver Gallbladder Duodenum Cecum Ileum • LES Pancreas • Pyloric Transverse colon Descending colon Jejunum Ascending colon Appendix Stomach • Ileal Sigmoid Rectum • IAS • EAS To Systemic Circulation Aorta LIVER HEPATIC Celiac (700) (200) STOMACH SPLEEN Portal (1800) Vein mls/min PANCREAS Superior Mesenteric (700) SMALL INTESTINE COLON Inferior Mesenteri c (400) Rates: ml/min Cross-Section of the Alimentary Canal Lymph node Villus Epithelium and Mucosa Muscularis mucosa Submucosa (contains most nerves and bloood vessels) Circular muscle Longitudinal muscle Myenteric plexus Submucosal plexus Gland in submucosa Serosa (connective tissue) •Epithelial Cell Barrier Microvilli: Brush Border Glycocalyx: Digestive Surface 1. Traps Nutrients 2. Increases Local Viscosity 3. Harbors Enzymes -Protective Barrier, Tight Junctions Neural Regulation of GI Function Autonomic Nervous System - INTRINSIC REGULATION: ENTERIC PLEXI - EXTRINSIC REGULATION: Central Nervous System Intrinsic Neural Regulation Myenteric ganglion Interganglionic fiber tract Circular muscle Submucosal ganglion Longitudinal Muscle 200 um Mucosa The Myenteric Plexus Signal Integration in the Plexi from CNS (-) to CNS (+) (+) Submucosal plexus S (-) S H+ G (+) Protein Pressure receptor Mucosa Autonomic Nervous System: Regulation of GI Function 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 of Vascular Smooth Muscle by Sympathetic Nerves: Inhibits Blood Flow Autonomic Nervous System Parasympathetic division Vagal nuclei Vagus nerves Sacral Spinal cord Pelvic nerves Pancreas and Gall Bladder Sympathetic division CNS Preganglionic fibers Sympathetic ganglia Postganglionic fibers Enteric nervous system Myenteric plexus Smooth muscle Submucosal plexus Secretory Endocrine cells (G) cells Blood vessels 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 To Systemic Circulation Aorta LIVER HEPATIC Celiac (700) (200) STOMACH SPLEEN Portal (1800) Vein mls/min PANCREAS Superior Mesenteric (700) SMALL INTESTINE COLON Inferior Mesenteri c (400) Rates: ml/min TABLE 1. Characteristics of the Major Gastrointestinal Hormones Name Composition Local Stimuli for Release Physiologic Circulating Action(s) Half-life • Gastrin G17 G34 peptide (2117 mw) peptides, amino acid secretion, peptide (3988 mw) acids, distention Gastric growth • Secretin peptide (3056 mw) duodenal acidity pancreatic bicarbonate secretion 3 min 12 min 3 min • 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 Glucose- dependent acids in the small insulinotropic peptide intestine 21 min • Secretin Family: Secretin VIP GIP Glucagon • Gastrin Family: Gastrin CCK Activates Adenylate Cyclase Increasing cAMP Increases Intracellular Ca2+ • Receptor Specificity Villous epithelium Blood vessels Lymph vessels Nerves Smooth muscle Connective tissue lymphocytes Plasma cells Eosinophiles Absorptive cells Goblet cells Crypt lumen Endocrine cells Muscularis mucosa Undifferentiated Goblet Mitoses Endocrine cells Paneth cells Crypt Epithelium SUMMARY OF HORMONE DISTRIBUTION Summary of Hormone Distributions SALIVARY GLANDS MOUTH ESOPHAGUS STOMACH BODY ANTRUM LIVER PANCREAS DUODENUM JEJUNUM ILEUM COLON K G GASTRIN I S GLUCOSE-DEPENDENT INSULINOTROPIC DeDDEPENDENT PEPTIDE CHOLECYSTOKINI SECRETIN N [ Hormone] in Blood Length of Intestine stimulated Candidate Hormones Peptide • Pancreatic polypeptide From, F-cells of pancreatic islets • Motilin • Enteroglucagon (GLP-1) Released by Intestinal Protein, Fat Glucose ? Intestinal Fat, Sugar Actions Inhibits Pancreatic HCO3and Enzyme Secretion Distal Gastric Motility Intestinal Motility ? Neurocrines: NANC Neurotransmitters Peptide • VIP Site of Action Mucosa and Smooth Muscle Actions Relaxes Muscle; Activates Cl- Channels • GRP or Bombesin Gastric Mucosa Stimulates Gastrin Release • Enkephalins Neurons in Mucosa and Visceral Muscle Increases Smooth Muscle Tone • Substance P • Neuropeptide Y • CCK Salivary Glands Neurons in Mucosa and Visceral Muscle Activates Blood Flow Decreases Secretion and Sphincter Tone Enteric and Hypothalamic Inhibits Propulsion Neurons Activates Satiety NANC: Non-Adrenergic Non-Cholinergic Paracrine Factor Location Actions • Somatostatin Stomach: Pyloric Gland Decreases Gastrin Secretion • Histamine* Stomach and Intestinal Mucosa Increases Gastric Acid Secretion Regulation of G-Cell Secretion Vagus nerves Myenteric Ach Ach Plexus + GRP Gastrin Gastrin Cell Digested Protein Ach Somatostatin Cell H+