Transverse Process Muscles: What Are They?

The transverse process is a wing-like projection of bone that allows back muscles and ligaments to attach to the spine. There are two transverse processes on each vertebra, one on each side. These processes provide attachment sites for muscles and ligaments that stabilize and move the spine. The transversospinalis muscle group, for example, functions in spinal stability, proprioception, and posture, while the semispinalis muscle group is responsible for rotation and lateral flexion of the spine. Several important muscles attach to the transverse processes, including the erector spinae muscles, multifidus, levator scapulae, and intertransversarii muscles.

The Transversospinalis muscle group is a deep group of back muscles that aid spinal stability, proprioception and posture

The semispinalis is the most superficial of the Transversospinalis muscles. It originates from the transverse process and crosses between four and six vertebrae to attach at the spinous process. The semispinalis has several parts, including the semispinalis thoracis, cervicis, and capitis. The cervicis, for example, is a thick mass of muscle that originates from the transverse processes of the upper five or six thoracic vertebrae. The semispinalis muscle has a unique function due to its attachment to the skull. Bilateral contraction of this muscle pulls the head backward and extends the neck and thoracic spine. Unilateral contraction, on the other hand, causes ipsilateral flexion of the neck and thoracic spine with contralateral rotation of the head.

The multifidus muscle lies deep to the semispinalis and spans the entire length of the vertebral column, with the greatest development in the lumbar region. The rotatores muscles lie beneath the multifidus and also run the full length of the spine, though they are most present in the thoracic region. These muscles are very small and quadrate-shaped, with eleven on each side of the spine. The rotatores, along with the multifidus and semispinalis, enable spinal rotation and extension. As they follow the spine's entire length, the rotatores are also involved with proprioception, or our sense of where we are in space.

The Transversospinalis muscles share the same nerve supply from the dorsal rami of the spinal nerves. They also share the same action, with bilateral contraction extending the spine, and unilateral contraction rotating the vertebral column to the opposite side. The Transversospinalis muscles, along with other deep back muscles, help to support and maintain the body's posture and produce movements of the head, neck, and trunk.

The semispinalis is the most superficial of the transversospinalis muscle group

The transversospinalis muscle group is a deep group of back muscles that help with spinal stability, proprioception, and posture. They also help to stabilize the vertebral column. The group consists of three subgroups: semispinalis, multifidus, and rotatores.

The semispinalis is the most superficial muscle in the transversospinalis group. It spans the thoracic and cervical regions of the vertebral column, with an attachment on the occipital bone of the skull. The semispinalis has the longest fascicles of the transversospinalis group, spanning six segments. The muscles in this group are the semispinalis capitis, semispinalis cervicis, and semispinalis thoracis.

The semispinalis capitis is innervated by the greater occipital nerve (posterior ramus of C2 spinal nerve) and spinal nerve C3. Bilateral contraction of the semispinalis capitis pulls the head posteriorly, while unilateral contraction pulls the head posteriorly and rotates the chin to the same side of the contracting muscle.

The semispinalis cervicis is a thick mass of muscle that originates from the transverse processes of the upper five or six thoracic vertebrae and may also arise from the articular processes of the lower four cervical vertebrae.

The semispinalis thoracis is innervated by the spinal nerve C3.

The deep back muscles, also called intrinsic or true back muscles, consist of four layers of muscles: superficial, intermediate, deep, and deepest layers. The transversospinalis group is part of the deep layer.

The multifidus muscle lies deep to the semispinalis and stabilises the vertebrae during local movements of the vertebral column

The multifidus muscle is a group of short, triangular muscles that, along with the semispinalis and rotatores, forms the transversospinalis muscle group. The transversospinalis muscle group functions in spinal stability, proprioception, and posture, stabilising the vertebral column. The semispinalis is the most superficial of the transversospinalis muscle group, with the multifidus lying deep to the semispinalis and the rotatores lying deep to the multifidus. The multifidus spans the whole length of the vertebral column, from the cervical to the lumbar spine, and is most developed in the lumbar region.

The multifidus muscle functions as an extensible ligament that stabilises the vertebrae during local movements of the vertebral column. It adapts its length to stabilise the vertebrae, acting as a dynamic ligament that adjusts small movements of the vertebral column. This ensures the efficient action of the long superficial muscles. The multifidus is also continuously active in upright postures and is probably active in all anti-gravity activity. When the oblique abdominal muscles contract to produce trunk rotation, some flexion of the trunk also occurs. The multifidus muscles oppose this trunk flexion, maintaining a pure axial rotation and acting as stabilisers during trunk rotation.

The transverse processes are small but significant parts of each vertebra, serving as attachment sites for the multifidus and other muscles and ligaments. They also serve as lever arms for the spinal muscles, aiding in movements such as rotation and lateral flexion. The transverse processes contribute to spinal stability and movement, with the lumbar vertebral region having elongated, horizontally flattened transverse processes that provide attachment sites for the large dorsal paraspinal muscles and the ventral psoas muscle group.

Weakness and atrophy of the multifidus muscle have been associated with chronic low back pain. Degenerative changes in the lumbar multifidus and erector spinae have been observed by imaging and have been linked to lumbar disc herniation and facet joint osteoarthritis. Treatment for multifidus-related conditions involves retraining the stabilising muscles of the core in a series of steps, including learning to isolate the muscle and co-contract it with the other muscles of the core.

The erector spinae muscles, including the iliocostalis, longissimus, and spinalis, extend and laterally flex the spine

The erector spinae muscles are a group of muscles that belong to the paraspinal muscles, which are located along the spine. The erector spinae muscles include three main muscles: the iliocostalis, longissimus, and spinalis. These muscles extend and laterally flex the spine and play an important role in spinal stability.

The iliocostalis muscles are the most lateral part of the erector spinae muscles and are attached to the ribs. They are responsible for the extension and lateral flexion of the spine. The iliocostalis muscles can be further divided into three sections: iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum.

The longissimus muscles form the middle part of the erector spinae muscles and are located lateral to the spinalis. They are the thickest and longest muscles in the group. The longissimus muscles have three regional groups: longissimus capitis, longissimus colli, and longissimus thoracis. The longissimus capitis and cervicis also function unilaterally to laterally flex the spine to the same side, while the longissimus capitis also helps to rotate the head to the same side.

The spinalis muscles are the most medially located muscles of the erector spinae, which means they are closest to the spine. The spinalis muscles receive blood supply from the vertebral, deep cervical, occipital, intercostal, and lumbar arteries. The function of the spinalis muscles is to extend and laterally flex the cervical and thoracic regions of the spine. Similar to the longissimus muscles, the spinalis muscles are also divided into three groups: spinalis capitis, spinalis cervicis, and spinalis thoracis.

The transversospinalis muscle group is a deep group of back muscles located behind the erector spinae. It includes the semispinalis, multifidus, and rotatores muscles. These muscles function in spinal stability, proprioception, and posture, stabilising the vertebral column.

The levator scapulae elevates the scapula and assists in neck rotation

The levator scapulae is a slender skeletal muscle situated at the back and side of the neck. It is a posterior axio-appenducular muscle, connecting the upper limb to the vertebral column. It is one of the muscles within the floor of the posterior triangle of the neck. The levator scapulae elevates the scapula and assists in neck rotation.

The levator scapulae originates from the transverse processes of the first four cervical vertebrae. The muscle fibres descend diagonally and laterally from their origin to insert at the superior angle and medial border of the scapula, between the superior angle and base of the spine of the scapula. The levator scapulae occupies the superficial layer of the superficial (extrinsic) back muscles. The upper part of the muscle lies underneath the splenius capitis and sternocleidomastoid muscles, while its lower part is covered by the trapezius. The levator scapulae is innervated by the cervical nerves C3-C4 and frequently also by the dorsal scapular nerve.

The main function of the levator scapulae is to elevate the scapula, as its Latin name suggests. When the spine is fixed, the levator scapulae elevates the scapula and rotates its inferior angle medially. It often works in combination with other muscles like the rhomboids, serratus anterior, serratus posterior superior and inferior muscles, pectoralis minor, and pectoralis major to produce downward rotation of the scapula and inferior rotation of the glenoid cavity. Elevating or rotating one shoulder at a time would require muscles to stabilise the cervical spine and keep it immobile so it does not flex or rotate.

The levator scapulae also assists in neck rotation. When the scapula is fixed, a contraction of the levator scapulae leads to the lateral flexion of the cervical vertebral column to the side and stabilises the vertebral column during rotation. When the cervical spine is fixed, the levator scapulae muscle helps in elevating and rotating the scapula such that the lateral angle moves inferiorly (i.e., rotates the point of the shoulder down). When the scapula is stabilised, contraction of this muscle laterally flexes and rotates the neck to the same side. Bilateral contraction of the levator scapulae helps in the extension of the cervical spine and neck.

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