Scalenus

Scalenus (also known as the Scalene muscles) are a group of three pairs of muscles in the lateral neck, namely the Scalenus anterior, Scalenus medius, and Scalenus posterior. The scalene muscles are lateral vertebral muscles that begin at the transverse processes of the cervical vertebrae of the neck and insert at the first and second ribs. These muscles function to flex and slightly rotate the neck. They also act as accessory muscles of respiration, along with the sternocleidomastoid muscle.

Anatomy

The scalene muscles are innervated by the anterior rami of the lower four cervical nerves. The brachial plexus and the subclavian artery pass between the anterior and middle scalene muscles, while the subclavian vein and the phrenic nerve pass anteriorly to the anterior scalene as it crosses over the first rib.

Function

The scalene muscles elevate the first and second ribs, aiding in respiration. They also function to bend the neck to the side and rotate the neck.

Clinical significance

Scalene muscles can be involved in several health conditions, including Scalene myofascial pain syndrome, a condition that can cause pain in the chest, shoulder, arm, and hand. The syndrome is thought to be a result of muscle imbalances and overuse.

Another condition that can involve the scalene muscles is Thoracic outlet syndrome (TOS). TOS is a condition in which the blood vessels or nerves in the space between the collarbone and the first rib (thoracic outlet) become compressed. This can cause pain in the shoulders and neck and numbness in the fingers.

See also

• Neck muscle
• Respiratory system

References

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Scalenus

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  Scalenus fasciatipennis
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  Darwinism 1889 page 259 image of mimicry