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The scalene muscles are a group of three closely related neck muscles: the anterior scalene, the middle scalene, and the posterior scalene. They are located in the posterior triangle of the neck and originate from the transverse processes of cervical vertebrae, inserting along the first and second ribs. The scalene muscles have an important relationship with other structures in the neck, such as the brachial plexus and subclavian artery, which pass between the anterior and middle scalenes. The muscles are prone to tension and are implicated in various neck problems, including torticollis, also known as wry neck.
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What You'll Learn
- The scalene muscles are a group of three closely related neck muscles
- The scalenes are made up of three pairs of muscles, with one set on each side of the body
- The anterior scalene muscle is the closest to the front
- The middle scalene is the largest and longest of the three scalene muscles
- The posterior scalene is the smallest and most deeply seated of the scalene muscles
The scalene muscles are a group of three closely related neck muscles
The scalene muscles have an important relationship with other structures in the neck. The brachial plexus and subclavian artery pass between the anterior and middle scalenes, while the subclavian vein and phrenic nerve pass anteriorly to the anterior scalene as the muscle crosses over the first rib. The phrenic nerve is oriented vertically, while the subclavian vein is oriented horizontally as they pass in front of the anterior scalene. The passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles constitute the scalene hiatus, also known as the scalene fissure.
The scalene muscles have multiple functions. They elevate the first and second ribs, laterally flex the neck, and act as accessory muscles of respiration. When the scalene muscles are healthy and working in a balanced way, they help support the upright posture of the cervical spine, which is the upper part of the spine. However, the scalene muscles are prone to tension and can cause neck problems such as torticollis, also known as wry neck, where the neck muscles stay contracted in chronically shortened positions.
The anterior scalene is located closest to the front and is considered an accessory breathing muscle because it lifts the first rib during inhalation. It also bends and rotates the neck when acting on one side and flexes the neck when both anterior scalenes work together. The middle scalene is the largest and longest of the three scalene muscles. It is separated from the anterior scalene by the subclavian artery and the ventral rami of the cervical spinal nerves. The posterior scalene is the smallest and most deeply seated of the scalene muscles. It is occasionally blended with the middle scalene.
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The scalenes are made up of three pairs of muscles, with one set on each side of the body
The scalene muscles are a group of three closely related neck muscles, with one set of muscles located on each side of the body. The three muscles are the anterior scalene, the middle scalene, and the posterior scalene. The scalenes are considered side neck muscles and are located in the posterior triangle of the neck.
The anterior scalene muscle is located closest to the front and lies deeply at the side of the neck, behind the sternocleidomastoid muscle. It arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae. It is inserted by a narrow, flat tendon into the scalene tubercle on the inner border of the first rib. The anterior scalene is considered an accessory breathing muscle because it lifts the first rib during inhalation. When acting on only one side of the neck, it can bend and rotate the neck, and when both sides work together, they flex the neck.
The middle scalene is the largest and longest of the three scalene muscles. It arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae. It descends along the side of the vertebral column and is inserted into the upper surface of the first rib. The clavicle and omohyoid muscle cross the middle scalene anteriorly, and it is separated from the anterior scalene by the subclavian artery and the ventral rami of the cervical spinal nerves.
The posterior scalene is the smallest and most deeply seated of the scalene muscles. It arises 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. It is occasionally blended with the middle scalene. The posterior scalene lifts the second rib and tilts the neck to the same side. It is also considered an accessory breathing muscle as it lifts the second rib during inhalation.
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The anterior scalene muscle is the closest to the front
The scalene muscles are a group of three muscles on each side of the neck, identified as the anterior, middle, and posterior. The scalene muscles have an important relationship with other structures in the neck. The brachial plexus and subclavian artery pass between the anterior and middle scalene muscles. The subclavian vein and phrenic 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.
The anterior scalene muscle (scalenus anterior) is the closest to the front. It is deeply placed, lying behind the sternocleidomastoid. It is located between the subclavian vein and the subclavian artery. The roots of the brachial plexus pass posterior to it. The phrenic nerve crosses its anterior surface. The anterior scalene can perform individually or in synergy with the other two scalenes. Bilateral contraction of the anterior scalene causes flexion of the neck. Unilateral contraction of the muscle causes ipsilateral flexion of the neck (to the same side). The anterior scalene can also elevate the first rib superiorly, expanding the antero-posterior diameter of the thorax. This makes it an accessory respiratory muscle. Ipsilateral contraction of the anterior scalene muscle results in lateral flexion of the neck to the same side, rotation of the neck to the opposite side, and elevation of the first rib during forced inspiration.
The scalenus anterior muscle sometimes gives off muscular slips that insert into the suprapleural membrane. These are known as the scalenus minimus (pleuralis) muscle, or the Albinus or Sibson muscle. It is a normal anatomical variant present within 7-46% of people. When present, the scalenus minimus muscle arises from the anterior border of the transverse process of the C7 vertebra. It inserts onto the inner border of the first rib behind the groove for the subclavian artery. Due to its pleural attachment, it is believed that this muscle tenses the pleural dome.
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The middle scalene is the largest and longest of the three scalene muscles
The scalene muscles are a group of three muscles on each side of the neck, identified as the anterior, middle, and posterior. They are named from the Ancient Greek "skalēnós", meaning "uneven" as the pairs are all of differing lengths. The scalene muscles have an important relationship with other structures in the neck.
The middle scalene, or scalenus medius, is the largest and longest of the three scalene muscles. It arises from the posterior tubercles of the transverse processes of the lower six cervical vertebrae. It descends along the side of the vertebral column and inserts by a broad attachment into the upper surface of the first rib, posterior to the subclavian groove. The middle scalene is covered by the sternocleidomastoid muscle. The lower half of the muscle is crossed by the omohyoid muscle, clavicle, subclavian artery, and anterior rami of the cervical spinal nerves.
The middle scalene is involved in the elevation of the first rib and flexion, lateral flexion, and rotation of the neck. It bends the neck to the same side as the acting muscle. The scalene muscles collectively act to elevate the first and second ribs, increasing the intrathoracic volume. In patients with respiratory distress, the scalene muscles may be used as accessory muscles of respiration to aid with breathing.
The brachial plexus and subclavian artery pass between the anterior and middle scalene muscles, constituting the scalene hiatus. This area is targeted with the administration of regional anesthesia prior to arm or shoulder surgery. The subclavian vein and phrenic nerve pass anteriorly to the anterior scalene as the muscle crosses over the first rib.
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The posterior scalene is the smallest and most deeply seated of the scalene muscles
The scalene muscles are a group of three closely related neck muscles: the anterior scalene, the middle scalene, and the posterior scalene. They are located in the posterior triangle of the neck and are considered side neck muscles. The scalenes are made up of three pairs of muscles, with one set located on either side of the body.
The posterior scalene is supplied by cervical nerves C5, C6, and C7, as well as the superficial cervical artery. The brachial plexus and/or the subclavian vessels can become compressed as they pass from the neck to the axilla in the region of the posterior scalene. This compression can lead to a range of symptoms known as thoracic outlet syndrome.
The function of the posterior scalene includes laterally flexing the lower end of the cervical portion of the vertebral column to the ipsilateral side and helping to elevate the second rib. When only one posterior scalene is contracting, it flexes and rotates the neck joints. When both posterior scalenes contract, they cause the neck to flex and raise the second rib, an action that may be difficult to detect while it is happening. The posterior scalene is considered an accessory breathing muscle as it lifts the second rib during inhalation.
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Frequently asked questions
Scalene muscles are a group of three closely related neck muscles: the anterior scalene, the middle scalene, and the posterior scalene. They are located in the posterior triangle of the neck and are considered side neck muscles.
The scalene muscles have multiple functions, including elevating the first and second ribs, laterally flexing and rotating the neck, and acting as accessory muscles of respiration. They also help support the upright posture of the cervical spine, which is the upper part of the spine.
The scalene muscles are implicated in several neck problems, including torticollis or wry neck, which is characterised by a twisted neck position that is difficult to release. Another issue is forward head posture or dowager's hump, which occurs when the anterior scalenes are tight and short, pulling the cervical vertebra forward.
