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The scalene are lateral vertebral muscles which begin at the first and second
ribs and pass up into the sides of the neck. There are three of these muscles. (1) The
"scalenus anterior muscle," which, when the neck is fixed, elevates the first
rib to aid in breathing or when the rib is fixed, bends the neck forward and sideways and
rotates it to the opposite side. (2) The "scalenus medius" is similar to the
scalenus anterior and raises the first rib from above or bends to slightly rotates the
neck from below. (3) The "scalenus posterior" raises the second rib or bends and
slightly rotates the neck. This muscle may be absent or may extend to the third rib. When
the scalene muscles are fixed from above, they elevate the first and second ribs to become
respiratory muscles for breathing. Acting from below, they bend the spinal column to the
same side or, if muscles act on both sides, the spinal column is slightly flexed.
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Very Scientific Version...
The scalenes vary in the number of their costal and vertebral
attachments, as well as in the interrelationships caused by the fusion of numerous
fasciculi. The problem of definition has been compounded by the
variety of descriptions of various muscles and their relation to the scalene mass by
various authors. Frequently (about 30% of cases) a poorly defined muscle mass is present.
The anterior scalene is sometimes located behind the subclavian artery or it may be split
into two parts for the arery to pass through between them. In such a case the muscle has
been seen pierced by the
eighth cervical nerve dorsal to the artery. These are potential entrapment sites for the
artery and the nerve. Bundles of muscle fibers may be exchanged between the anterior and
the middle scalene. The
anterior scalene may also be closely associated with the anterior intertransverse muscles,
and slips may be exchanged between them. The same is true in the case of longus capitis
(rectus capitis anterior
major).
The muscle scalenus pleuralis (Sibson) or minimus (Albinus) is a frequent variation. When
present this muscle arises from the transverse process of the seventh cervical vertebrae
(occasionally also from
the the sixth), and extends to the inner border of the first rib and the fascia supporting
the cervical dome of pleura. When absent the muscle is represented by a fibrous band
(Sibson's fascia or the lig.
costo-pleuro-vertebralis of Zuckerkandl). Another variant, the transversalis cervicis
medius, arises from the transverse processes of the second, and fourth cervical vertebrae
and courses between the
middle and posterior scalenes to insert onto the seventh cervical and first thoracic
vertebrae.
Typically the anterior scalene arises from the fourth, fifth and sixth cervical vertebrae
(anterior tubercles), occasionslly from the third, and rarely from the seventh. When the
anterior scalene is doubled, one of
them is termed accessory anterior scalene.
Mori found the anterior scalene arose from the anterior tuberculum of the transverse
processes of cervical vertebrae as follows: from 2,3,4,5, on the right side and the left
side, both 4 cases (3.3%); 3,4,5, on
the right side 53 times and on the left 55 times (45%); 4,5,6, on the right side 63 times
and on the left 61 (51.6%) from 120 cadavers, 240 sides.
By vertebra of origin:
Second cervical, 8 sides, 33.3%,
Third cervical, 116 sides, 48.3%,
Fourth cervical, 240 sides, 100%,
Fifth cervical, 240 sides, 100%, and
Sixth cervical, 124 sides, 51.6%.
The tendon of all of Mori's cases inserted onto the scalenus tubercle on the upper surface
of the body of the first rib, although it has been found to insert on the second or third
ribs.
The middle scalene arises from the costotransverse lamellae of the lower five cervical
vertebrae. It arises, in about 80% of cases, from the axis, in about 60% from the atlas,
and in about 10% from the seventh
cervical vertebra.
The posterior scalene may arise from the third, fourth, and the seventh cervical
vertebrae, as well as from the usual fifth and sixth; it inserts on the second and
occasionally from the third rib. The posterior
scaleme is frequently fused with the middle scalene and the first external intercostal
muscle. In Mori's cases (51 cadavers, 102 sides) scalenus posterior inserted as follows:
Rib 1; right side 9, left side 13, total 21, 21.5%.
Rib 1 and 2; right side 37, left side 34, total 71, 69.6%
Rib 1, 2, and 3; right side 5, left side 4, total 9, 8.8%.
The scalene muscles as a whole are considered as the intercostal muscles of the thorax,
located in the neck. Owing to the absence of free ribs the three parts have merged and
resemble the abdominal wall,
except that they do not have a distinct division between them.
Syn.: m. Sc. ant.: scalenus anticus, scalenus prior (Albinus), scalenus primus (Krause).
Sc. med. : scalenus secundus. Sc. post. : scalenus tertius (Krause), scalène
posterieur.
References
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McGraw-Hill Book Company. New York.
Bochdalek, Jr. (1867) Vor dem Musculus sacalenus anticus ihren Verlauf nehmende Art.
subclavia dextra. Arch. Path. Anat. Physiol. Klin. Med. 41:261-263.
Boyd, G.I. (1933-34) Abnormality of the subclavian artery associated with the presence of
the scalenus minimus. J. Anat. 68:280-281.
Cave, A.J.E. (1933) A note on the origin of the m. scalenus medius. J. Anat. 67:480-483.
Fawcett, E. (1896) What is Sibson's muscle (scalenus pleuralis)? J. Anat. Physiol.
30:433-436.
Gilis, P. (1891) Note sur l'anatomie des muscles scalènes. Soc. Biol., Comptes
Rendus Hebdomadaires des Séances et Mémories. 43:223-226.
Henle, J. (1871) Handbuch der Muskellehre des Menschen, in Handbuch der systematischen
Anatomie des Menschen. Verlag von Friedrich Vieweg und Sohn, Braunschweig.
Iwate, S. (1930) On the scalenus minimus. Juzenkai Zasshi. 35:2567-2574. In Japanese.
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scalene muscles. Ann. Surg. 127:1182-1201.
Latarjet, A. (1948) Testut's TraitÈ d'Anatomie Humaine, 9th ed.. G. Doin & Cie.,
Paris.
Macalister, A. (1875) Observations on muscular anomalies in the human anatomy. Third
series with a catalogue of the principal muscular variations hitherto published. Trans.
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Nat, B.S. (1924) The scalenus muscle. J. Anat. 58:268-270.
Nishi, S. (1916-17) Report of the dissection in the Tohoku medical college. Tohoku Igakkai
Zasshi. 1:64-66, 392-396. In Japanese.
Nishi, S. (1953) Miologie de la japano. Statistika raporto pri muskolanomalioj ce japanoj.
The Gunma Journal of Medical Sciences 2:1-13. In Japanese.
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Schaefer, E. A., Symington, J. and T.H. Bryce., Eds. (1923) Quain's Elements of Anatomy,
11th ed. , Longmans, Green and Co., London.
Sebileau, P. (1891) Le muscle scalène. Soc. Biol., Comptes Rendus Hebdomadaires
des Séances et Mémoires. 43:201-221.
Shore, L.R. (1926) An example of the muscle scalenus minimus. J. Anat. 60:418-419.
Stott, C. F. (1928) A note on the scalenus minimus muscle. J. Anat. 65:359-361.
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