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Spinalis Muscle Anatomy

The spinalis muscle forms a crucial component of the deep muscles of the back, specifically within the erector spinae group. This intricate muscle complex plays a vital role in spinal extension and postural maintenance, making it particularly relevant for clinicians treating musculoskeletal conditions.

Spinalis Muscle Anatomy

The spinalis muscle divides into three distinct portions: spinalis thoracis, spinalis cervicis, and spinalis capitis.

The spinalis thoracis, the largest segment, originates from the spinous processes of T11-L2 vertebrae and inserts into the spinous processes of the upper thoracic vertebrae.

The spinalis cervicis originates from T1-T2 and inserts into the C2-C4.

While the spinalis capitis connects the upper thoracic region to the occipital bone. It originates from spinous processes of C7 – T1 vertebrae and inserts into the occipital bone (midline).

Spinalis Muscle

Innervation and Blood Supply

Primary innervation comes through the posterior rami of spinal nerves corresponding to each vertebral level. The blood supply primarily derives from the posterior intercostal arteries, with additional contributions from the deep cervical and vertebral arteries for the cervical portions.

Function & Action

Bilateral contraction of the Spinalis Muscle extends the head, cervical and thoracic spines, while unilateral contraction acts to ipsilateral lateral flexion of cervical and thoracic spine.

See Also: Spine Movements
OriginCapitis: spinous processes of C7 – T1 vertebrae
Cervicis: spinous processes of C7 – T1 vertebrae; nuchal ligament
Thoracis: spinous process of T11 – L2
InsertionCapitis: occipital bone (midline)
Cervicis: spinous process of C2 – C4 vertebrae
Thoracis: spinous process of T2 – T8 vertebrae
InnervationLateral branch of posterior rami of spinal nerves
Blood SupplyPosterior branch of posterior intercostal artery
Deep cervical artery
Muscular branches of vertebral artery
ActionBilateral contraction: extension of head, cervical and thoracic spines
Unilateral contraction: ipsilateral lateral flexion of cervical and thoracic spine

Clinical Significance

Understanding spinalis muscle anatomy proves essential in diagnosing and treating various spinal conditions. Dysfunction commonly manifests as localized pain, reduced range of motion, and postural abnormalities. Clinicians should consider this muscle group when evaluating patients with thoracic spine pain or cervicogenic headaches.

Imaging Considerations

MRI and CT imaging provide detailed visualization of the spinalis muscle, particularly useful in identifying pathological changes. T1-weighted MRI sequences typically offer optimal visualization of muscle architecture and potential fatty infiltration.

Therapeutic Implications

Treatment approaches focusing on the spinalis muscle often incorporate specific exercise protocols and manual therapy techniques. Understanding the precise anatomical relationships helps clinicians target interventions more effectively, particularly in cases of chronic spinal pain or postural dysfunction.

References:

  1. Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 42nd Edition
    https://www.elsevier.com/books/grays-anatomy/standring/978-0-7020-7710-5
  2. Journal of Anatomy: Deep Muscles of the Back
    https://onlinelibrary.wiley.com/journal/14697580
  3. Clinical Anatomy of the Spine, Spinal Cord, and ANS
    https://www.sciencedirect.com/book/9780323079549/clinical-anatomy-of-the-spine-spinal-cord-and-ans
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