The Digestive System and Body Metabolism
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Transcript of The Digestive System and Body Metabolism
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The Digestive System and Body Metabolism
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The Digestive System FunctionsIngestion—taking in foodDigestion—breaking food down both
physically and chemicallyAbsorption—movement of nutrients into
the bloodstreamDefecation—rids the body of indigestible
waste
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Organs of the Digestive SystemTwo main groups
Alimentary canal (gastrointestinal or GI tract)—continuous coiled hollow tube
Accessory digestive organs
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Organs of the Digestive System
Figure 14.1
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Organs of the Alimentary CanalMouthPharynxEsophagusStomachSmall intestineLarge intestineAnus
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Mouth (Oral Cavity) AnatomyLips (labia)—protect the anterior openingCheeks—form the lateral wallsHard palate—forms the anterior roofSoft palate—forms the posterior roofUvula—fleshy projection of the soft palate
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Mouth (Oral Cavity) AnatomyVestibule—space between lips externally
and teeth and gums internallyOral cavity proper—area contained by the
teethTongue—attached at hyoid bone and
styloid processes of the skull, and by the lingual frenulum to the floor of the mouth
TonsilsPalatineLingual
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Mouth (Oral Cavity) Anatomy
Figure 14.2a
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Mouth PhysiologyMastication (chewing) of foodMixing masticated food with salivaInitiation of swallowing by the tongueAllows for the sense of taste
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Pharynx AnatomyNasopharynx—not part of the digestive
systemOropharynx—posterior to oral cavityLaryngopharynx—below the oropharynx
and connected to the esophagus
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Pharynx Anatomy
Figure 14.2a
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Pharynx PhysiologyServes as a passageway for air and foodFood is propelled to the esophagus by two
muscle layersLongitudinal inner layerCircular outer layer
Food movement is by alternating contractions of the muscle layers (peristalsis)
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Esophagus Anatomy and PhysiologyAnatomy
About 10 inches longRuns from pharynx to stomach through the
diaphragmPhysiology
Conducts food by peristalsis (slow rhythmic squeezing)
Passageway for food only (respiratory system branches off after the pharynx)
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Layers of Alimentary Canal OrgansFour layers
MucosaSubmucosaMuscularis externaSerosa
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Layers of Alimentary Canal OrgansMucosa
Innermost, moist membrane consisting ofSurface epitheliumSmall amount of connective tissue
(lamina propria)Small smooth muscle layer
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Layers of Alimentary Canal OrgansSubmucosa
Just beneath the mucosaSoft connective tissue with blood vessels,
nerve endings, and lymphatics
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Layers of Alimentary Canal OrgansMuscularis externa—smooth muscle
Inner circular layerOuter longitudinal layer
Serosa—outermost layer of the wall contains fluid-producing cellsVisceral peritoneum—outermost layer that is
continuous with the innermost layerParietal peritoneum—innermost layer that
lines the abdominopelvic cavity
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Alimentary Canal Nerve PlexusesTwo important nerve plexuses serve the
alimentary canalBoth are part of the autonomic nervous
systemSubmucosal nerve plexusMyenteric nerve plexus
Function is to regulate mobility and secretory activity of the GI tract organs