| Scalene muscles | |
|---|---|
 The anterior vertebral muscles. | |
| Details | |
| Origin | Cervical vertebrae (CII-CVII) |
| Insertion | First andsecondribs |
| Artery | Ascending cervical artery (branch ofInferior thyroid artery) |
| Nerve | Cervical nerves (C3-C8) |
| Actions | Elevation offirst andsecondribs |
| Identifiers | |
| Latin | mm. scalenii |
| FMA | 64829 |
| Anatomical terms of muscle | |
Thescalene muscles are a group of threemuscles on each side of theneck, identified as the anterior, the middle, and the posterior. They are innervated by the third to the eighth cervicalspinal nerves (C3-C8).
The anterior and middle scalene muscles lift thefirst rib and bend theneck to the side they are on. The posterior scalene lifts the second rib and tilts the neck to the same side.
The muscles are named from theAncient Greekσκαληνός (skalēnós), meaning 'uneven'.
The scalene muscles are attached at one end tobony protrusions onvertebrae C2 to C7 and at the other end to the first and secondribs.[1]
Theanterior scalene muscle (Latin:scalenus anterior), lies deeply at the side of the neck, behind thesternocleidomastoid muscle. It arises from the anterior tubercles of thetransverse processes of the third, fourth, fifth, and sixthcervical vertebrae, and descending, almost vertically, is inserted by a narrow, flat tendon into thescalene tubercle on the inner border of thefirst rib, and into the ridge on the upper surface of thefirst rib in front of thesubclavian groove. It is supplied by theanterior ramus ofcervical nerve 5 and 6.
Themiddle scalene, (Latin:scalenus medius), is the largest and longest of the three scalene muscles. The middle scalene arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae. It descends along the side of thevertebral column to insert by a broad attachment into the upper surface of the first rib, posterior to the subclavian groove. Thebrachial plexus and thesubclavian artery pass anterior to it.
Theposterior scalene, (Latin:scalenus posterior) is the smallest and most deeply seated of the scalene muscles. It arises, by two or three separate tendons, from the posterior tubercles of the transverse processes of the fourth, fifth and sixth cervical vertebrae, and is inserted by a thin tendon into the outer surface of the second rib, behind the attachment of the anterior scalene. It is supplied by cervical nerves C5, C6 and C7. It is occasionally blended with the middle scalene.
A fourth muscle, thescalenus minimus (Sibson's muscle), is sometimes present behind the lower portion of the anterior scalene.[2]
The anterior and middle scalene muscles lift thefirst rib and bend theneck to the same side as the acting muscle;[3] the posterior scalene lifts the second rib and tilts the neck to the same side.
Because they elevate the upper ribs, they also act asaccessory muscles of respiration, along with thesternocleidomastoids.
The scalene muscles have an important relationship to other structures in the neck. Thebrachial plexus andsubclavian artery pass between the anterior and middle scalenes.[4] Thesubclavian vein andphrenic nerve pass anteriorly to the anterior scalene as the muscle crosses over the first rib. The phrenic nerve is oriented vertically as it passes in front of the anterior scalene, while the subclavian vein is oriented horizontally as it passes in front of the anterior scalene muscle.[4]
The passing of thebrachial plexus and thesubclavian artery through the space of the anterior and middle scalene muscles constitute the scalene hiatus (the term "scalene fissure" is also used). The region in which this lies is referred to as the scaleotracheal fossa. It is bounded by theclavicle inferior anteriorly, the trachea medially, posteriorly by thetrapezius, and anteriorly by theplatysma muscle.
The anterior and middle scalene muscles can be involved in certain forms ofthoracic outlet syndrome as well asmyofascial pain syndrome, the symptoms of which may mimic aspinal disc herniation of thecervical vertebrae.[5]
Since the nerves of the brachial plexus pass through the space between the anterior and middle scalene muscles, that area is sometimes targeted with the administration of regional anesthesia by an anesthesia provider. The nerve block, called aninterscalene block, may be performed prior to arm or shoulder surgery.[6]
According to the medical codes in the 2016 Procedural Coding Expert, published by theAmerican Academy of Professional Coders, forCurrent Procedural Terminology (CPT) and other medical codes, the scalenus anticus muscle can be divided by reparative or reconstructive surgery, with (# 21705) or without (# 21700) resection of thecervical rib.
The scalenes used to be known as thelateral vertebral muscles.[7]
The muscles are named fromGreekσκαληνός (skalēnós), meaning 'uneven'[8] as the pairs are all of differing length.[2]
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