Transcript Hormone: Classical Definition. A Chemical Messenger Produced

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+