Muscles of abdomen

... apply to tracheal systems. Some high-metabolism insects have specific abdomen-contracting muscles to squeeze air out of the system, but many don't have a dedicated pump. Often, too, ...

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... the job of controlling suckling in infants, which uses primarily mouth muscles and ensures that milk does not get into the lungs. Another possibility ... makes negative pressure in the chest but positive pressure in the abdomen and thus tends to force stomach contents into the esophagus, which ...

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