Serratus Anterior
| Pronuncation | ser-RAY-tus |
| Derivation | Saw-toothed, as in serrated, describing its attachments on the ribs. |
| Origin | Upper eight or nine ribs. |
| Insertion | Under the scapula to its medial edge. |
| Action | Moves the scapula laterally, and rolls its inferior angle upward to raise the arm above the shoulder. |
The visible portion of serratus anterior lies over the ribs next to external oblique. The attachments of these two muscles come together like interlaced fingers. Only the lowest three or four bands can be seen; the rest lie under latissimus dorsi and the muscles of the chest.
The bands are wider than the ribs themselves, but generally follow their curve. As such, they can be useful for determining the shape of the ribcage. The bands of external oblique, by comparison, drop off at a sharper 45-degree angle.
Serratus anterior has a pronounced effect on the form of latissimus dorsi. It fills out the form on the lateral side, and there is a plane break under the last band that extends from the inferior angle of the scapula to the front of the ribcage.