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The scalene muscles are a set of three muscles: the anterior scalene, the middle scalene, and the posterior scalene. They are located in the posterior triangle of the neck and play a role in neck flexion, rib elevation, and respiration. The posterior scalene is the smallest and most deeply located of the scalene muscles, sometimes blending with the middle scalene. This article will focus on the posterior scalene muscle, exploring its attachments, function, and clinical relevance.
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What You'll Learn
- Posterior scalene muscle attachments and their relation to the cervical vertebrae
- The origin of the posterior scalene muscle in the posterior tubercles
- The insertion of the posterior scalene muscle on the second rib
- The blood supply to the posterior scalene muscle
- The role of the posterior scalene muscle in neck movement
Posterior scalene muscle attachments and their relation to the cervical vertebrae
The scalene muscles are a group of three muscles located on each side of the neck: scalenus anterior, scalenus medius, and scalenus posterior. These muscles are deep and positioned laterally to the cervical tract. They are involved in neck movement and head posture maintenance.
The scalenus posterior, or posterior scalene, originates from the posterior tubercles of the transverse processes of the cervical vertebrae C5-C7. In some cases, it may involve cervical vertebrae C3 and C4 as well. The muscle fibres extend posterolaterally and insert into the external surface of the second rib, specifically on its anterior face. The insertion site is located posterior to the attachment of the serratus anterior muscle.
The scalenus medius, or middle scalene, originates from the transverse processes of cervical vertebrae C2-C7, inserting itself on the upper face of the first rib. The insertion site is located posterior to the groove for the subclavian artery.
The scalenus anterior, or anterior scalene, originates from the anterior tubercles of the transverse processes of cervical vertebrae C3-C6. It is found in the lateral part of the neck, anterior to the subclavian artery, and related to various structures in the neck.
The cervical vertebrae, specifically the transverse processes, serve as the origin of attachment for the scalene muscles. These muscles work together to facilitate neck movement and maintain head posture. Dysfunction in the scalene muscles can lead to pathological conditions such as thoracic outlet syndrome, decreased ventilatory capacity, and cervical pain.
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The origin of the posterior scalene muscle in the posterior tubercles
The scalene muscles are a group of three muscles on each side of the neck, namely the anterior, middle, and posterior. They are also referred to as the lateral vertebral muscles. These muscles are involved in neck movement and head posture maintenance. They also act as accessory breathing muscles.
The posterior scalene is the smallest and deepest of the scalene muscles. It originates from the posterior tubercles of the transverse processes of the cervical vertebrae C5-C7. In some cases, the posterior scalene may involve cervical vertebrae from C3 to C4 as well. The muscle extends posterolaterally and tapers into a thin tendon, which inserts into the external surface of the second rib. The site of insertion is located behind the attachment of the serratus anterior muscle.
The posterior scalene is supplied by cervical nerves C5, C6, and C7. The innervation to the posterior scalene is delivered by the anterior rami of spinal nerves C6-C8. The posterior scalene receives its vascular supply from the ascending cervical branch of the inferior thyroid artery. It also receives some blood from the superficial branch of the transverse cervical artery, a branch of the thyrocervical trunk.
The posterior scalene lifts the second rib and tilts the neck to the same side. The unilateral contraction of the posterior scalene results in ipsilateral lateral flexion of the neck. The posterior scalene is involved in several pathological patterns, such as thoracic outlet syndrome, decreased ventilatory capacity, and cervical pain.
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The insertion of the posterior scalene muscle on the second rib
The scalene muscles are a group of three muscles on each side of the neck, namely the scalenus anterior (anterior scalene), scalenus medius (middle scalene), and scalenus posterior (posterior scalene). They are the accessory muscles of respiration, elevating the ribs during forced inspiration. They also play a role in neck movement and maintaining the posture between the neck and the head.
The posterior scalene muscle is the smallest of the scalene muscles. Its fibres originate from the posterior tubercles of the transverse processes of cervical vertebrae C5-C7. The muscle extends posterolaterally and tapers into a thin tendon, which inserts into the external surface of the second rib. The site of insertion is located posterior to the attachment of the serratus anterior muscle.
The scalenus posterior muscle is innervated by the anterior rami of spinal nerves C6-C8. The contraction of the scalenus medius muscle produces strong ipsilateral flexion of the neck. In the same manner, as the scalenus anterior, this muscle helps to stabilize or raise the first rib during respiration, when its vertebral attachment is fixed. The scalenus medius is the largest and longest of the scalenes. It originates from the transverse processes of axis (C2), transverse processes of atlas (C1), and the posterior tubercles of transverse processes of the vertebrae C3-C7.
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. 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.
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The blood supply to the posterior scalene muscle
The scalenus posterior muscle is innervated by the anterior rami of spinal nerves C6-C8. It receives its blood supply from the ascending cervical branch of the inferior thyroid artery. The posterior scalene also receives some blood from the superficial branch of the transverse cervical artery, a branch of the thyrocervical trunk.
The scalene muscles are a group of three pairs of muscles in the lateral neck: scalenus anterior, scalenus medius, and scalenus posterior. Sometimes, a fourth muscle, the scalenus minimus, is present behind the lower portion of the scalenus anterior. The scalene muscles are located in the posterior triangle of the neck, beneath the prevertebral fascia within the floor of the posterior triangle of the neck. They are a set of three muscles (anterior, middle, and posterior scalenes) lying deep to the sternocleidomastoid. The scalene muscles attach between the first and second ribs and the transverse processes of the cervical vertebrae.
The scalenus posterior muscle originates from the posterior tubercles of the transverse processes of the last three or four cervical vertebrae. It fits on the anterior face of the second rib. In about 30% to 71% of the population, there is a fourth scalene or minimum scalene, affecting the anterior tubercle of the transverse process of the seventh cervical vertebra, to insert itself on the first rib and the Sibson’s fascia posteriorly, which covers the pleural dome.
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The role of the posterior scalene muscle in neck movement
The scalene muscles are three paired muscles (anterior, middle, and posterior) located in the lateral aspect of the neck. They are involved in neck movement and play a role in maintaining the posture of the neck and head.
The posterior scalene is the smallest and deepest of the scalene muscles. It originates from the posterior tubercles of the transverse processes of the last three or four cervical vertebrae (C5-C7 or C3-C7) and fits onto the anterior face of the second rib.
The posterior scalene muscle is involved in neck flexion and lateral flexion. Ipsilateral contraction of the posterior scalene causes ipsilateral lateral flexion of the neck. Bilateral contraction of the scalene muscles causes anterior flexion of the neck.
The scalene muscles also play a role in respiration. They are secondary or accessory respiratory muscles, aiding in breathing during forced inspiration. During a forced inspiratory act, the scalene muscles lift the first two ribs, thereby increasing the intrathoracic volume. The posterior scalene specifically elevates the second rib.
In addition to their role in neck movement and respiration, the scalene muscles are also involved in maintaining the posture of the neck and head. Their dysfunction can lead to pathological conditions such as thoracic outlet syndrome, decreased ventilatory capacity, and cervical pain.
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Frequently asked questions
The posterior scalene, or scalenus posterior, is one of the three lateral muscles of the neck, belonging to the scalene group. It is the smallest and most deeply seated of the scalene muscles.
The posterior scalene originates from the posterior tubercles of the transverse processes of the fourth, fifth and sixth cervical vertebrae.
The posterior scalene inserts by a thin tendon into the anterior or outer surface of the second rib, behind the attachment of the anterior scalene.
The function of the posterior scalene is to elevate the second rib and tilt or flex the neck to the same side. It also acts as an accessory muscle of respiration, elevating the ribs during forced inspiration.
