| Figure 24.13
d |
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| Circular
muscles |
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| contract
pushing |
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| bolus down |
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| Peristalsis Along |
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| Esophagus |
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| There is no |
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| gastroesophageal
(or |
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| cardiac)
sphincter! The |
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| esophageal
muscles at |
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| the lower end
of the |
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| esophagus
remain |
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| tonically
contracted until |
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| peristalsis
brings the |
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| bolus of food.
These |
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| muscles
produce a |
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| functional
but not a |
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| structural
sphincter. |
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| Longitudinal |
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| muscles
shorten |
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| passageway
ahead |
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| of bolus |
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