Serratus posterior inferior inserts on which ribs?

Serratus posterior inferior inserts on which ribs?

• A. Inferior border of ribs 8-12
• B. Superior border of ribs 3-6
• C. Medial border of ribs 7-9
• D. Lateral surface of ribs 9-12

Answer: (A)

The mechanism being tested is where this muscle attaches and how that guides its action. The serratus posterior inferior reaches the lower ribs by attaching along their inferior borders, typically the bottom four ribs (the lower ribs). Because it pulls on the underside of those ribs when it contracts, it helps depress them during expiration, aiding in increasing thoracic pressure. This insertion pattern—on the inferior borders of ribs eight through twelve—fits the muscle’s role and line of pull. Describing the insertion as the superior border, medial border, or a lateral surface would place the attachment in locations that don’t match this muscle’s actual pull, so those descriptions aren’t correct for serratus posterior inferior.

The mechanism being tested is where this muscle attaches and how that guides its action. The serratus posterior inferior reaches the lower ribs by attaching along their inferior borders, typically the bottom four ribs (the lower ribs). Because it pulls on the underside of those ribs when it contracts, it helps depress them during expiration, aiding in increasing thoracic pressure. This insertion pattern—on the inferior borders of ribs eight through twelve—fits the muscle’s role and line of pull.

Describing the insertion as the superior border, medial border, or a lateral surface would place the attachment in locations that don’t match this muscle’s actual pull, so those descriptions aren’t correct for serratus posterior inferior.