Dominic Stone
The scalene muscles are a group of three muscles on each side of the neck: the anterior, middle, and posterior. They are named after the Greek word 'skalenos', meaning 'uneven'. The scalene muscles act as accessory muscles of respiration and perform flexion at the neck. They are innervated by the third to the eighth cervical spinal nerves (C3-C8). The scalene muscles also 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 scalene muscles. This space is often targeted with regional anaesthesia before arm or shoulder surgery.
| Characteristics | Values |
|---|---|
| Number of muscles | 3 (anterior, middle, and posterior) |
| Location | Lateral aspect of the neck |
| Function | Accessory muscles of respiration, flexion at the neck, elevation of the first and second ribs |
| Innervation | Third to eighth cervical spinal nerves (C3-C8) |
| Blood supply | Ascending cervical branch of inferior thyroid artery |
| Anatomical landmarks | Brachial plexus and subclavian artery pass between the anterior and middle scalene muscles |
| Clinical significance | Interscalene block for regional anesthesia, scalene syndrome |
| Variants | Scalenus minimus (Sibson's muscle) |
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What You'll Learn
- The scalenes are a group of three muscles on each side of the neck: anterior, middle, and posterior
- The scalenes act as accessory muscles of respiration and perform flexion at the neck
- The brachial plexus and subclavian artery pass between the anterior and middle scalenes
- The scalenes are sometimes targeted with the administration of regional anaesthesia
- The scalenes may be used as 'accessory muscles of respiration' to aid breathing in patients with respiratory distress
The scalenes are a group of three muscles on each side of the neck: anterior, middle, and posterior
The scalenes are a group of three muscles on each side of the neck: the scalenus anterior, scalenus medius (middle), and scalenus posterior. These muscles originate from the transverse processes of the cervical vertebrae and attach to the first and second ribs. The anterior and middle scalene muscles lift the first rib, while the posterior scalene lifts the second rib.
The scalenes are named from the Ancient Greek word "σκαληνός" (skalēnós), meaning "uneven", as the pairs are all of differing lengths. They form an uneven triangle, known as the scalene triangle, with the anterior scalene forming the anterior border, the posterior scalene forming the posterior border, and the first rib forming the inferior border. This space is anatomically significant as it is traversed by the trunks of the brachial plexus and the subclavian artery.
The scalenes act as accessory muscles of respiration, elevating the first and second ribs to increase intrathoracic volume and aid in forced inspiration or inhalation during strenuous activities such as running or hiking uphill. They also play a role in neck movement, with the anterior and middle scalenes bending the neck to the same side as the acting muscle, and the posterior scalene tilting the neck to the same side.
The scalenes are important in clinical practice. For example, in upper limb surgery, local anaesthetic can be injected between the anterior and middle scalene muscles to perform an interscalene block, avoiding the need for general anaesthesia. Additionally, trigger points in the scalenes can cause chest pain and breathing difficulties, leading to concern for cardiac issues.
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The scalenes act as accessory muscles of respiration and perform flexion at the neck
The scalene muscles are a group of three muscles on each side of the neck: the scalenus anterior, scalenus medius, and scalenus posterior. The scalenus minimus is sometimes also present, but it is not very common. The scalene muscles act as accessory muscles of respiration and perform flexion at the neck.
The scalene muscles are attached at one end to bony protrusions on vertebrae C2 to C7 and at the other end to the first and second ribs. The scalenus anterior originates from the anterior tubercles of the transverse processes of C3-C6 and attaches to the scalene tubercle on the inner border of the first rib. The 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 and inserts into the upper surface of the first rib. The scalenus posterior is the smallest and most deeply seated of the scalene muscles. It arises from the posterior tubercles of the transverse processes of C5-C7 and attaches to the second rib.
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. By increasing intrathoracic volume, patients can ventilate their lungs more effectively. However, the scalene muscles are not required for respiration in healthy individuals, so their use is a clinical sign of respiratory distress.
The scalene muscles also assist in flexion at the neck. The scalenus anterior and medius lift the first rib and bend the neck to the side they are on. The scalenus posterior lifts the second rib and tilts the neck to the same side. The scalene muscles also help control head and neck movement during yoga poses, such as warrior pose and halasana.
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The brachial plexus and subclavian artery pass between the anterior and middle scalenes
The scalene muscles are a group of three muscles on each side of the neck, namely the anterior, middle, and posterior. They are innervated by the third to the eighth cervical spinal nerves (C3-C8). The scalene muscles act as accessory muscles of respiration and perform flexion at the neck.
The brachial plexus is a network of nerve fibres that supplies the skin and musculature of the upper limb. It is formed by the anterior rami of cervical spinal nerves C5, C6, C7, and C8, and the first thoracic spinal nerve, T1. The roots of the brachial plexus are formed by the anterior rami of spinal nerves C5-T1. The trunks of the brachial plexus emerge between the anterior and middle scalene muscles.
The subclavian vein and phrenic nerve pass anteriorly to the anterior scalene muscle. The phrenic nerve is critical for diaphragm movement and plays a key role in respiration. The subclavian vein is oriented horizontally as it passes in front of the anterior scalene. The subclavian artery is located posterior to the anterior scalene.
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. In upper limb surgery, the brachial plexus can be infiltrated with local anaesthetic to avoid the use of a general anaesthetic. This is also known as an interscalene block.
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The scalenes are sometimes targeted with the administration of regional anaesthesia
The scalene muscles are a group of three muscles on each side of the neck, identified as the anterior, middle, and posterior. They are innervated by the third to the eighth cervical spinal nerves (C3-C8). The scalenes act as accessory muscles of respiration and perform flexion at the neck. They collectively act to elevate the first and second ribs, increasing the intrathoracic volume.
The scalene muscles are sometimes targeted with the administration of regional anaesthesia. Regional anaesthesia is one of the four main categories of anaesthesia used during surgery and other procedures, the other three being general anaesthesia, sedation, and local anaesthesia. Regional anaesthesia is further divided into spinal anaesthesia, epidural anaesthesia, and nerve blocks. Spinal anaesthesia involves the placement of a local anaesthetic in or around the central nervous system (CNS), which comprises the brain and spinal cord. The first regional anaesthetic technique performed was spinal anaesthesia, which was first performed in 1898 in Germany by August Bier.
The scalene muscles are targeted with regional anaesthesia due to the passing of the brachial plexus and the subclavian artery through the space of the anterior and middle scalene muscles. This region is referred to as the scalene hiatus or scalene fissure. The nerve block used in this case is called an interscalene block, which may be performed prior to arm or shoulder surgery. During an interscalene block, local anaesthetic is injected between the muscles at the level of the cricoid cartilage.
The administration of regional anaesthesia to the scalene muscles is a safe and effective procedure that can provide targeted pain relief to the patient. It is important to note that the use of regional anaesthesia may vary depending on the specific surgical procedure and the patient's preferences.
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The scalenes may be used as 'accessory muscles of respiration' to aid breathing in patients with respiratory distress
The scalene muscles are a group of three muscles on each side of the neck: the anterior, middle, and posterior. They are named after the Greek word "skalenos", meaning "uneven", as the pairs are all of differing lengths. The scalene muscles act as accessory muscles of respiration and perform flexion at the neck. They are attached at one end to bony protrusions on vertebrae C2 to C7 and at the other end to the first and second ribs.
The anterior and middle scalene muscles lift the first rib and bend the neck to the side they are on. The posterior scalene lifts the second rib and tilts the neck to the same side. The scalene muscles are innervated by the third to the eighth cervical spinal nerves (C3-C8). The blood supply to all scalene muscles comes from the ascending cervical branch of the inferior thyroid artery.
In patients with respiratory distress, the scalene muscles may be used as accessory muscles of respiration to aid breathing. By elevating the first and second ribs, the scalenes increase the intrathoracic volume, allowing the patient to ventilate their lungs more effectively. This is particularly useful in situations where more air is needed in the lungs, such as during strenuous exercise, running, or hiking up a steep hill.
The scalene muscles are important in anaesthetics and upper limb surgery as the brachial plexus and subclavian artery pass between the anterior and middle scalene muscles. This allows for the administration of regional anaesthesia by targeting the area between these muscles.
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Frequently asked questions
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 after the Greek word 'skalenos', meaning 'uneven'.
The scalene muscles collectively act to elevate the first and second ribs, increasing intrathoracic volume. They also act as accessory muscles of respiration, aiding with breathing in situations where we need to get more air into our lungs.
To stretch the scalene muscles, it is recommended to lie supine (face up) and gently pull the head and neck so that the neck tilts to the opposite side of the side being stretched. To target the posterior scalene, turn your face toward the arm that is pulling. To target the anterior scalene, turn your face away from the pulling arm. To target the middle scalene, look straight up or slightly toward the pulling arm.
