What is the action of serratus posterior superior?

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Multiple Choice

What is the action of serratus posterior superior?

Explanation:
The key idea is that serratus posterior superior acts as an accessory muscle of respiration. Its fibers pull the upper ribs upward when it contracts, specifically elevating ribs 2–5 to expand the thoracic cavity during inspiration. This action increases the thoracic volume to help with inhalation. It does not depress the ribs or extend or rotate the spine—the latter actions belong to other back muscles like the erector spinae and vertebral rotators. So elevating the ribs during respiration best describes its function.

The key idea is that serratus posterior superior acts as an accessory muscle of respiration. Its fibers pull the upper ribs upward when it contracts, specifically elevating ribs 2–5 to expand the thoracic cavity during inspiration. This action increases the thoracic volume to help with inhalation. It does not depress the ribs or extend or rotate the spine—the latter actions belong to other back muscles like the erector spinae and vertebral rotators. So elevating the ribs during respiration best describes its function.

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