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M01.09.004 Deep Muscles
The deep intrinsic muscles of the back, collectively known as the transversospinales, lie underneath the erector spinae muscles. These short muscles are primarily associated with the transverse and spinous processes of the vertebral column.
Components
The group consists of three major muscles:
- Semispinalis
- Multifidus
- Rotatores
Additionally, there are minor deep intrinsic muscles, which play supplementary roles in stabilizing and supporting the vertebral column.
Detailed Anatomy of Major Muscles
1. Semispinalis
The semispinalis is the most superficial muscle in the transversospinales group, divided into thoracic, cervicis, and capitis parts.
| Feature | Details |
|---|---|
| Attachments | Originates from the transverse processes of C4–T10. Ascends 4–6 segments, attaching to spinous processes (C2–T4) and the occipital bone. |
| Innervation | Posterior rami of spinal nerves. |
| Actions | Extends and contralaterally rotates the head and vertebral column. |
2. Multifidus
The multifidus is located beneath the semispinalis and is most developed in the lumbar region.
| Feature | Details |
|---|---|
| Attachments | Originates from the sacrum, posterior iliac spine, mamillary processes (lumbar), transverse processes (T1–T3), and articular processes (C4–C7). Ascends 2–4 vertebral segments, attaching to spinous processes. |
| Innervation | Posterior rami of spinal nerves. |
| Actions | Stabilizes the vertebral column. |
3. Rotatores
The rotatores are the deepest muscles in this group and are most prominent in the thoracic region.
| Feature | Details |
|---|---|
| Attachments | Originates from transverse processes. Ascends to attach to lamina and spinous processes of the vertebra above. |
| Innervation | Posterior rami of spinal nerves. |
| Actions | Contributes to extension, rotation, stabilization, and proprioception of the vertebral column. |
Minor Deep Intrinsic Muscles
| Muscle | Attachments | Actions |
|---|---|---|
| Interspinales | Between adjacent spinous processes. | Stabilizes the vertebral column. |
| Intertransversarii | Between adjacent transverse processes. | Stabilizes the vertebral column. |
| Levatores Costarum | From transverse processes of C7–T11 to the rib below. | Elevates the ribs. |
Points to Remember
- The transversospinales group consists of semispinalis, multifidus, and rotatores, which act primarily on the vertebral column.
- Semispinalis spans 4–6 vertebrae, multifidus spans 2–4 vertebrae, and rotatores spans 1–2 vertebrae.
- All these muscles are innervated by the posterior rami of spinal nerves.
- These muscles play crucial roles in stabilization, extension, rotation, and proprioception of the spine.
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