transversus thoracis (triangularis sterni, sternocostalis)

Origin

• dorsal surface of xiphoid cartilage
• lower part of dorsal surface of body of sternum

Insertion

5th to 6th costal cartilages

Action

contributes to depression of the ribs, narrowing chest

Innervation

intercostal nerves

More general terms

• skeletal muscle (voluntary muscle)