1 — Second rib [II]; 2 — First rib [I]; 3 — Scalenus anterior; Anterior scalene; 4 — Scalenus posterior; Posterior scalene; 5 — Scalenus medius; Middle scalene; 6 — Longus colli; 7 — Atlas [CI]; 8 — Rectus capitis anterior; 9 — Rectus capitis lateralis; 10 — Longus capitis; 11 — Scalene
tubercle; 12 — Groove for subclavian artery