1 — Subcostales; 2 — Sternum; 3 — External intercostal muscle; 4 — Internal intercostal muscle; 5 — Scalenus posterior; Posterior scalene; 6 — Scalenus anterior; Anterior scalene; 7 — Scalenus medius; Middle scalene; 8 — Axis [CII]; 9 — Atlas [CI]; 10 — Vertebra prominens [CVII];
11 — First rib [I]; 12 — Costal cartilage