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The scalene muscles are a group of three muscles on each side of the neck, namely the anterior, middle, and posterior. They are located in the lateral aspect of the neck, extending from the vertebrae to the first and second ribs. The scalene muscles act as accessory muscles of respiration, elevating the first and second ribs and increasing intrathoracic volume. They also facilitate neck movement and contribute to postural stability between the neck and head. The scalene muscles have significant surgical importance, particularly in anaesthetics and upper limb surgery, due to their proximity to major vessels and nerves.
| Characteristics | Values |
|---|---|
| Number of Scalene Muscles | 3 (anterior, middle and posterior) |
| Location | Lateral aspect of the neck |
| Function | Accessory muscles of respiration, perform flexion at the neck, elevate the first and second ribs |
| Innervation | Brachial plexus, cervical plexus, cervical spinal nerves (C3-C8) |
| Blood Supply | Ascending cervical branch of inferior thyroid artery |
| Surgical Importance | Identification of subclavian artery, brachial plexus, and phrenic nerve |
| Anatomical Variations | Scalenus minimus (Sibson's muscle) may be present in 7-46% of people |
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What You'll Learn
- The scalene muscles are a group of three muscles on each side of the neck
- They are important in central venous catheterisation and upper limb surgery
- The scalene muscles act as accessory muscles of respiration and breathing
- The scalene muscles are involved in head and neck movement and postural stability
- The anterior, middle and posterior scalene muscles have distinct functions and attachments
The scalene muscles are a group of three muscles on each side of the neck
The scalene muscles are deep and positioned laterally in the neck, enclosed by the deep fascia, also known as the prevertebral fascia. They are attached to bony protrusions on vertebrae C2 to C7 and the first and second ribs. The anterior scalene muscle, in particular, is located deep to the sternocleidomastoid on the lateral aspect of the neck. It originates from the anterior tubercles of the transverse processes of C3 to C6 and attaches to the scalene tubercle on the inner border of the first rib.
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 inserts into the upper surface of the first rib, posterior to the subclavian groove. The brachial plexus and subclavian artery pass anteriorly to the middle scalene.
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 C5 to C7 and inserts into the second rib. The posterior scalene elevates the second rib and tilts the neck to the same side. The trunks of the brachial plexus are visible emerging between the anterior and middle scalene muscles.
The scalene muscles have significant surgical importance. The anterior scalene serves as a landmark for identifying the subclavian artery, the brachial plexus, and the phrenic nerve. Understanding the anatomy and function of the scalene muscles helps clinicians manage various conditions in the cervicothoracic area.
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They are important in central venous catheterisation and upper limb surgery
The scalene muscles are three paired muscles (anterior, middle and posterior) located in the lateral aspect of the neck. They act as accessory muscles of respiration and perform flexion at the neck.
The scalene muscles are important in central venous catheterization via the subclavian approach. Their proximity to major vessels increases the risk of vascular or nerve injury. Understanding the anatomy, function, and clinical significance of the scalene muscles helps clinicians manage various conditions in the cervicothoracic area.
Central venous catheterization is a standard and often necessary procedure for critically ill patients. It involves inserting a central venous catheter (CVC), an indwelling device, into a large central vein. The CVC is advanced until the terminal lumen resides within the inferior vena cava, superior vena cava, or right atrium. Central venous catheters allow for the administration of vasoactive medications and agents known as venous irritants. They are also used to perform dialysis or plasmapheresis or as a conduit to insert additional devices for more complex procedures.
The scalene muscles are also relevant in upper limb surgery. The brachial plexus can be infiltrated with local anaesthetic to avoid the use of a general anaesthetic – known as an interscalene block. To do this, local anaesthetic is injected between these muscles at the level of the cricoid cartilage.
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The scalene muscles act as accessory muscles of respiration and breathing
The scalene muscles are three paired muscles (anterior, middle, and posterior) located in the lateral aspect of the neck. They form part of the floor of the posterior triangle of the neck. The scalene muscles act as accessory muscles of respiration and breathing.
The scalene muscles collectively act to elevate the first and second ribs, increasing the intrathoracic volume. In patients with respiratory distress, the scalene muscles aid with breathing by increasing intrathoracic volume, allowing patients to ventilate their lungs more effectively. However, the scalene muscles are not required for respiration in healthy individuals, and their use is a clinical sign of respiratory distress. The scalene muscles are also relevant in central venous catheterization via the subclavian approach due to their proximity to major vessels, which can increase the risk of vascular or nerve injury.
The scalene muscles respond to unilateral stimulation, and their exact mechanism remains unclear. However, inspiration involving the lower ribs likely recruits the scalene muscles to support breathing. The scalene muscles extend from the vertebrae to the first and second ribs and are enclosed by the deep fascia, also known as the prevertebral fascia. The anterior scalene originates from the anterior tubercles of the transverse processes of the third to sixth cervical vertebrae and inserts onto the scalene tubercle on the inner border of the first rib. The middle scalene is the largest and longest of the three scalene muscles, with several long, thin muscle bellies arising from the cervical spine and converging into one large belly that inserts into the first rib. The posterior scalene is the smallest and deepest of the scalene muscles, inserting into the second rib.
The scalene muscles also play a role in inspiration, with all three types involved in breathing. The scalenus anterior contributes to the elevation of the first rib. The scalenus medius is the most significant for breathing in this group, running from the transverse processes of the axis and the transverse process of C3 to C7 until the first rib, also raising it. The scalenus posterior passes from the posterior tubercles of the transverse process of C4-6 to the second rib, helping to elevate it.
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The scalene muscles are involved in head and neck movement and postural stability
The scalene muscles are three paired muscles (anterior, middle, and posterior) located in the lateral vertebral region of the neck. They are responsible for several functions, including head and neck movement and postural stability.
The scalene muscles contribute to the complex functional role of the neck and head. These muscles facilitate accessory breathing by elevating the first and second ribs during forced inspiration, thereby increasing the intrathoracic volume and aiding respiration in patients with respiratory distress. The scalene muscles also play a role in lateral neck flexion, allowing movement of the head from side to side.
The anterior scalene muscle, in particular, serves as a key anatomical landmark. It aids in identifying the subclavian artery, the brachial plexus, and the phrenic nerve, which runs vertically along its anterior surface. The scalene muscles, as a group, receive innervation from both the brachial plexus and the cervical plexus, contributing to their diverse functions.
The scalenes are involved in maintaining postural stability between the neck and head. Their deep position in the neck and their lateral orientation make them crucial for supporting the weight of the head and allowing for smooth neck movements. Dysfunction of these muscles can lead to pathological conditions such as thoracic outlet syndrome (TOS), reduced ventilatory capacity, and cervical pain.
The scalene muscles are susceptible to injuries like whiplash due to their constant involvement in neck movements. Rest, ice packs, and limited neck movement are recommended for healing strained scalene muscles. Additionally, trigger points in these muscles can cause chest pain and breathing difficulties, often leading to concerns about cardiac symptoms.
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The anterior, middle and posterior scalene muscles have distinct functions and attachments
The scalene muscles are three paired muscles located in the lateral aspect of the neck. They form part of the floor of the posterior triangle of the neck. These muscles are the scalenus anterior (anterior scalene), scalenus medius (middle scalene) and scalenus posterior (posterior scalene).
The anterior scalene is located deep to the sternocleidomastoid on the lateral aspect of the neck. It originates from the anterior tubercles of the transverse processes of C3-C6 and attaches onto the scalene tubercle on the inner border of the first rib. The anterior scalene is also related to many structures of the neck, including the suprapleural membrane, pleura, roots of the brachial plexus, and the subclavian artery. It serves as a key landmark for identifying the subclavian artery, the brachial plexus, and the phrenic nerve.
The middle scalene is the largest and longest of the three scalene muscles. It originates from the transverse processes of C2-C7 and attaches onto the superior aspect of the first rib. The middle scalene receives its blood supply from the ascending cervical branch of the inferior thyroid artery.
The posterior scalene is the smallest and deepest of the scalene muscles. It originates from the posterior tubercles of the transverse processes of C5-C7 and attaches onto the second rib.
The scalene muscles collectively act to elevate the first and second ribs, increasing the intrathoracic volume. They are accessory muscles of respiration, performing flexion, lateral flexion, and rotation of the neck.
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Frequently asked questions
The scalene muscles are a group of three muscles on each side of the neck, namely the anterior, middle, and posterior.
The scalene muscles collectively act to elevate the first and second ribs, increasing the intrathoracic volume. They also facilitate accessory breathing and contribute to neck and head movement, as well as postural stability between the neck and head.
The scalene muscles have significant surgical importance. They serve as landmarks for identifying nearby anatomical structures such as the subclavian artery, brachial plexus, and phrenic nerve. Additionally, they are relevant in central venous catheterization and other surgical procedures due to their proximity to major vessels and nerves.
