Dominic Stone
The scalene muscles are a group of three pairs of muscles in the lateral neck: scalenus anterior, scalenus medius, and scalenus posterior. They are also referred to as the lateral vertebral muscles. Sometimes, a fourth muscle, the scalenus minimus, is present in 30% to 71% of individuals. These muscles are involved in neck movement, postural stability, and accessory breathing. The scalene muscles attach to bony protrusions on vertebrae C2 to C7 and the first and second ribs.
| Characteristics | Values |
|---|---|
| Number of scalene muscles | 3 or 4 |
| Names of scalene muscles | Scalenus anterior, scalenus medius, scalenus posterior, scalenus minimus |
| Location of scalene muscles | Lateral neck |
| Function | Accessory breathing, neck and head movement, postural stability between the neck and head |
| Attachments | Cervical vertebrae C2-C7, first and second ribs |
| Innervation | Brachial plexus, cervical plexus, anterior rami of spinal nerves C5-C8 |
| Blood supply | First portion of the subclavian artery |
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What You'll Learn
- Anterior scalene: Originates from C3-C6, attaches to the first rib
- Middle scalene: Originates from C2-C7, attaches to the first rib
- Posterior scalene: Originates from C5-C7, attaches to the second rib
- Scalenus minimus: Inserts into the first rib and Sibson fascia
- Scalenes' relationship with other structures: Brachial plexus and subclavian artery pass between the anterior and middle scalenes
Anterior scalene: Originates from C3-C6, attaches to the first rib
The scalene muscles are three paired muscles of the lateral neck: the anterior, middle, and posterior scalene muscles. The scalene muscles collectively act to elevate the first and second ribs, increasing intrathoracic volume. In patients with respiratory distress, the scalene muscles may be used as 'accessory muscles of respiration' to aid with breathing.
The anterior scalene muscle is located deep to the sternocleidomastoid on the lateral aspect of the neck. It originates from the anterior tubercles of the transverse processes of the third to sixth cervical vertebrae (C3-C6). The muscle then descends and is inserted by a narrow, flat tendon into the scalene tubercle on the inner border of the first rib. The anterior scalene is the anteriormost of the three scalene muscles.
The anterior scalene serves as a key landmark for identifying the subclavian artery, the brachial plexus, and the phrenic nerve, which courses along its anterior surface. The phrenic nerve is oriented vertically as it passes in front of the anterior scalene, while the subclavian vein is oriented horizontally. The omohyoid muscle crosses over both the anterior and middle scalene muscles.
The anterior scalene can be targeted with specific head and neck movements. To target the anterior scalene, one can lie supine with the head elevated and rotated to the contralateral side, and with the hands raised above the head. From here, the individual can gently pull their head and neck to tilt to the opposite side, relaxing the neck muscles.
The scalene muscles can be involved in certain forms of thoracic outlet syndrome, and dysfunction can lead to pathological conditions such as reduced ventilatory capacity and cervical pain. Medical interventions often aim to decrease excessive muscle tone, while rehabilitation may focus on restoring physiological length or enhancing contractile strength.
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Middle scalene: Originates from C2-C7, attaches to the first rib
The scalene muscles are a group of three pairs of muscles in the lateral neck: scalenus anterior, scalenus medius, and scalenus posterior. The middle scalene, or scalenus medius, originates from the posterior tubercles of the transverse processes of the cervical vertebrae C2-C7. It attaches to the first rib, inserting into the superior surface of the first rib, behind the subclavian artery sulcus.
The middle scalene is the largest and longest of the three scalene muscles. It is involved in the elevation of the first rib. When the vertebral attachment is fixed, the contraction of the middle scalene muscle produces a strong ipsilateral flexion of the neck. The scalene muscles collectively act to elevate the first and second ribs, increasing the intrathoracic volume. This can aid in breathing for patients with respiratory distress.
The scalene muscles are deep and positioned laterally in the neck. They have a complex functional role, facilitating accessory breathing and contributing to neck and head movement, as well as postural stability between the neck and head. Dysfunction of these muscles can lead to pathological conditions such as thoracic outlet syndrome (TOS), reduced ventilatory capacity, and cervical pain.
The brachial plexus and subclavian artery pass between the anterior and middle scalene muscles, constituting the scalene hiatus. This region is referred to as the scalene fissure or scaleotracheal fossa. The subclavian vein and phrenic nerve pass anteriorly to the anterior scalene as the muscle crosses over the first rib.
A fourth scalene muscle, the scalenus minimus, is present in approximately 30% to 71% of individuals. This muscle arises from the anterior tubercle of the transverse process of the seventh cervical vertebra (C7) and inserts into the first rib and the Sibson fascia.
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Posterior scalene: Originates from C5-C7, attaches to the second rib
The scalene muscles are three paired muscles of the lateral neck: the scalenus anterior, scalenus medius, and scalenus posterior. The scalenus posterior, or posterior scalene, is the smallest and most deeply seated of the scalene muscles. It originates from the posterior tubercles of the transverse processes of cervical vertebrae C5-C7 and attaches to the second rib.
The posterior scalene is responsible for elevating the second rib and causing ipsilateral lateral flexion of the neck. It is also an accessory muscle of respiration, aiding breathing in patients with respiratory distress. By increasing intrathoracic volume, patients can ventilate their lungs more effectively.
The scalene muscles are deep and positioned laterally in the neck. They facilitate accessory breathing and contribute to neck and head movement, as well as postural stability between the neck and head. Dysfunction of these muscles can lead to pathological conditions such as thoracic outlet syndrome (TOS), reduced ventilatory capacity, and cervical pain.
The posterior scalene is innervated by the anterior rami of spinal nerves C5, C6, and C7, and occasionally C8. It is supplied by cervical nerves C5, C6, and C7. The muscle extends posterolaterally and tapers into a thin tendon, which inserts into the external surface of the second rib.
The scalene muscles are named from the Greek σκαληνός (skalēnós), meaning 'uneven', as the pairs are all of differing lengths.
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Scalenus minimus: Inserts into the first rib and Sibson fascia
The scalene muscles are a group of three pairs of muscles in the lateral neck: scalenus anterior, scalenus medius, and scalenus posterior. The scalenus anterior muscle is the anteriormost of the three scalene muscles. It originates from the anterior tubercles of the transverse processes of the vertebrae C3-C6 and inserts on the scalene tubercle of the superior surface of the first rib. The scalenus medius is the largest and longest of the three scalene muscles. It originates from the transverse processes of the vertebrae C2-C7 and inserts on the superior surface of the first rib. The scalenus posterior is the smallest and deepest of the scalene muscles. It originates from the posterior tubercles of the transverse processes of C5-C7 and attaches to the second rib.
In some individuals, a fourth scalene muscle, the scalenus minimus, is present in approximately 30% to 71% of people. This muscle arises from the anterior tubercle of the transverse process of the seventh cervical vertebra and inserts on the first rib and the Sibson fascia posteriorly, which covers the pleural dome. The scalenus minimus can be mistaken for the transverse pleural ligament. The muscle helps elevate the first rib during inhalation, contributing to the expansion of the thoracic cavity. It may also play a role in flexing the neck laterally when acting together with other scalene muscles. The scalenus minimus helps stabilize the cervical spine during head and neck movements.
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Scalenes' relationship with other structures: Brachial plexus and subclavian artery pass between the anterior and middle scalenes
The scalene muscles are a group of three paired muscles on each side of the neck, namely the scalenus anterior, scalenus medius, and scalenus posterior. Sometimes, a fourth muscle, the scalenus minimus, is present in 30% to 71% of individuals. The scalene muscles act as accessory muscles of respiration and perform flexion at the neck.
The scalene muscles have an important relationship with other structures in the neck. The trunks of the brachial plexus are visible emerging between the anterior and middle scalene muscles. The brachial plexus and subclavian artery pass between the anterior and middle scalene muscles. This provides an important anatomical landmark in anaesthetics for performing an interscalene block. 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 passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles constitute the scalene hiatus (or scalene fissure).
The scalene muscles receive blood supply from the first portion of the subclavian artery, referred to as the "prescalene area." The subclavian artery is located posterior to the anterior scalene. The scalene muscles are also important landmarks for identifying the subclavian artery, the brachial plexus, and the phrenic nerve.
The middle scalene may be perforated by brachial plexus branches, such as C7 and C8, which terminate at the posterior scalene. TOS arises from direct or indirect mechanical compression of the subclavian vessels or the brachial plexus between the clavicle, scalene muscles, and first rib. The most common symptoms include fatigue, pain, and paresthesias affecting the upper extremity.
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Frequently asked questions
The anterior scalene muscle originates from the anterior tubercles of the transverse processes of the third to sixth cervical vertebrae and attaches to the scalene tubercle on the inner border of the first rib.
The middle scalene muscle originates from the posterior tubercles of the transverse processes of the second to seventh cervical vertebrae and attaches to the upper surface of the first rib.
The posterior scalene muscle originates from the posterior tubercles of the transverse processes of the fifth to seventh cervical vertebrae and attaches to the outer surface of the second rib.
The scalenus minimus muscle arises from the anterior tubercle of the transverse process of the seventh cervical vertebra and attaches to the first rib and the Sibson fascia.
