Page 1
SublingualSalivary glands:
Submaxillary
LiverGallbladder
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
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Aorta
(200)
Celiac(700)
PortalVein
Superior Mesenteric (700)
InferiorMesenteri
c (400)
LIVER
STOMACH
SPLEEN
PANCREAS
SMALLINTESTINE
COLON
To Systemic Circulation
(1800) mls/min
HEPATIC
Rates:
ml/min
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Lymph node
Myenteric plexusSubmucosal plexus Gland in
submucosa
Villus
Epithelium and Mucosa
Muscularis mucosa
Submucosa (contains most nerves
and bloood vessels)
Circular muscleLongitudinal muscle
Serosa (connective tissue)
Cross-Section of the Alimentary Canal
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•Epithelial Cell Barrier
Microvilli: Brush Border Glycocalyx: Digestive Surface
1. Traps Nutrients2. Increases Local Viscosity3. Harbors Enzymes
-Protective Barrier, Tight Junctions
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- INTRINSIC REGULATION: ENTERIC PLEXI
- EXTRINSIC REGULATION: Central Nervous System
Autonomic Nervous System
Neural Regulation of GI Function
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Interganglionicfiber tract
Myentericganglion
Circular muscle
Submucosalganglion
200 um
Mucosa
LongitudinalMuscle
Intrinsic Neural Regulation
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The Myenteric Plexus
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(-)
G
(+)(+)
to CNS
(+)
S(-)
Protein
from CNS
Submucosalplexus
Pressurereceptor
Mucosa
S
H+
Signal Integration in the Plexi
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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
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Vagalnuclei
SacralSpinal cord
Pelvic nerves
Vagusnerves
Enteric nervous system
CNSPreganglionic
fibers
Postganglionic fibers
Myentericplexus
Submucosalplexus
Smoothmuscle
Secretorycells
Endocrine(G) cells
Bloodvessels
Parasympatheticdivision Sympathetic
division
Sympatheticganglia
Pancreas andGall Bladder
Autonomic Nervous System
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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
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Aorta
(200)
Celiac(700)
PortalVein
Superior Mesenteric (700)
InferiorMesenteri
c (400)
LIVER
STOMACH
SPLEEN
PANCREAS
SMALLINTESTINE
COLON
To Systemic Circulation
(1800) mls/min
HEPATIC
Rates:
ml/min
Page 13
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
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• Secretin Family: Activates Adenylate Cyclase Secretin Increasing cAMP
VIP GIP
Glucagon
• Gastrin Family: Increases Intracellular Ca2+
Gastrin CCK
• Receptor Specificity
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Blood vesselsLymph vesselsNervesSmooth muscleConnective tissuelymphocytesPlasma cellsEosinophiles
Villousepithelium
Undifferentiated GobletMitosesEndocrine cells
Paneth cells
CryptEpithelium
Cryptlumen
Muscularismucosa
Absorp-tive cells
Gobletcells
Endocrine cells
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Summary of Hormone Distributions
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[ Hormone] in
Blood
Length of Intestinestimulated
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Peptide Released by Actions
• Pancreatic polypeptide Intestinal Inhibits Pancreatic HCO3-
Protein, Fat and Enzyme Secretion Glucose
• Motilin ? Distal Gastric Motility Intestinal Motility
• Enteroglucagon (GLP-1) Intestinal ? Fat, Sugar
From, F-cells of pancreatic islets
Candidate Hormones
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• VIP Mucosa and Relaxes Muscle; Smooth Muscle Activates Cl-
Channels
• GRP or Gastric Mucosa Stimulates Gastrin Bombesin Release
• Enkephalins Neurons 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
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Factor Location Actions
• Somatostatin Stomach: Decreases Gastrin Pyloric Gland Secretion
• Histamine* Stomach and Increases Gastric Intestinal Mucosa Acid Secretion
Paracrine
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AchAch
AchGRP
Vagus nerves
GastrinGastrin
Cell
Somato-statinCell
DigestedProtein H+
+
Regulation of G-Cell Secretion
Myenteric
Plexus