Soft Tissue of the Back

Innervation

As a general rule, muscles associated with the back are innervated by the dorsal rami of the spinal nerves

They are innervated segmentally and near their origin

Only a couple of exceptions

Innervation

Innervation

The Exceptions

Serratus Posterior Superior• Lig. Nuchae and spinous processes of C7-T3

to 2nd to 5th ribs Serratus Posterior Inferior

• Spinous Proceses of T11-L2 to inferior borders of last 4 ribs

Elevate or depress ribs (accessory respiratory muscles)

Innervated by ventral rami

Serratus Post.

Major Groups of Back Muscles

Those that arise from the mid-line and run superiorly and laterally – The Splenius Muscles (Bandage)

Those that arise from near the mid-line or slightly laterally and run almost longitudinally with no marked inward or outward slant – called the Erector Spinae

Major Groups

The third group are those that arise laterally and run towards the mid-line as they travel up• Called the Transversospinalis group

Last – small muscles that run from one spinous process to another or one transverse process to another (interspinales and intertransvesus)

Splenius Muscles Splenius Capitis

• Lig. Nuchae and Spinous Process of C7-T4 to sup. Nuchal line and mastoid process

Splenius Cervicis• Spinous processes of T3-T6 to Transvers process of C2-C4

Both extend head and neck and can laterally flex (side bend) the head; Also support and can contribute to rotation of cervical spine and, thus, the head

Dorsal rami of spinal nerves nearest their respective origins

Splenius

Erector Spinae

Long Muscles with multiple, overlapping, origins Three sub groups; iliocostalis, longissimus,

spinalis Common “origin” of the entire group is a muscle

mass located on the posterior sacrum, iliac crest, and spinous process of lumbar vertebrae

Beyond that, specific muscles have various attachments

Erector Spinae

E. Spinae

E. Spinae

The three groups are broken down into sub -subgroups based upon where they are located

E.G., in the lumbar region called lumborum, in thoracic region called thoracis, in cervical region called cervicis and, if they reach anywhere on the skull, they are called capitis.

E.G., Iliocostalis lumborum

E. Spinae

Overlap or multiple attachments Despite the common “origin” of the group,

most muscles have various and multiple origins and insertions

These tend to overlap so that the group can traverse a large length of the back

Some components will attach as an insertion while new fibers will originate from the same region

E. Spinae

For example, the iliocostalis lumborum muscles will attach to the lower six ribs while the iliocostalis thoracis will originate from the lower six ribs and insert on the upper six ribs

Likewise the iliocostalis cervicis will originate from the upper six ribs and insert on the transverse process of C4 thru C6

All are innervated by the dorsal rami of the nerves nearest their origin – e.g., iliocostalis thoracis will be innervated by the lower thoracic nerves (T6-T12)

Longissimus

Generally, run from the transverse processes of one level of v. column up several levels to attach to another transverse process

The longissimus capitis originates on t. processes of T1-T4 and attach to the skull at the mastoid process, hence the name capitis

Is the only E.Spinae to attach to skull

Spinalis

E. Spinae nearest the mid-line, hence, the name spinalis

The spinalis group run from spines of one group of vetebrae to spines of v. several segments up

Most prominent in thoracic spine but also located in cervical and lumbar spine

General, Collective, Function of E. Spinae

To support spine (anti-gravity) To extend spine To laterally flex spine (side bend) To rotate the spine They work together

Transversospinalis Group

Arise laterally and run, more or less, to the mid-line

Semispinalis Capitis• Transverse Process C7-T6 to Occipital bone, near

mid-line, Extend head, rotate to same side

Semispinalis Cervicis• Transverse process T1-T6 to Spines of C2-C6, Extend

head (Cervical Spine) and side bend

Semispinalis

Semispinalis

Transversospinalis Group

Multifidi From the sacrum, and transverse

process of L., T. and lower C vertebrae to Spinous Process of Lumbar, thoracic and cervical vetebrae 2 or 3 levels up

Very large and obvious in lumbar region Support V. column. May contribute to

minor motions (lat. flex., rot., ext.)

Rotatores

Transverse processes of 2nd cervical to sacrum to lamina on vertebrae above origin (one segment)

Same function as multifidi

Interspinous and Intertransversus

Run between spinous processes or transverse processes

Blend with ligaments of same name Perform same function (Stability)

Small Muscles

Muscles mostly associated with the head

Sub-Occipital (Posterior) Triangle very small, support head on v. column, minor motions

Rectus Capitis Post. Major• Spinous process of C2 to Lateral aspect of nuchal line

• Dorsal ramus of suboccipital nerve

Rectus capitis Post. Minor• Post. Arch of atlas (C1) to med. aspect of inferior

nuchal line

• Dorsal ramus of suboccipital nerve

Sub-Occ. Triangle

Obliqus Capitis Superior• Transverse process Atlas to a point between

sup. and inf. Nuchal line

Obliqus Capitis Inferior• Spinous Process Axis to transverse process

atlas

Suboccipital Triangle

Anterior Muscles – all innervated by Ventral Rami

Sterno-Cleido-Mastoid Manubrium (S) and Medial ½ clavicle to

mastoid process Together – head flexion, unilaterally, side

bending (same side) rotation (opposite side)

CN XI and ventral rami of C2, C3

SCM

SCM - Anterior

Scaleni-AKA Pre-Vertebral

Scalaneus Anterior Ant tubercle of transverse process of C2-C6 Scalene tubercle of anterior surface of 1st rib Flex and rotate spine Reverse action = accessory respiratory muscle

by raising 1st rib. ventral rami C2-C6

Pre-Vertebrals

Scaleni

Scaleneus Medius from post. tubercle of transverse processes C2-C7 to sup. surface of 1st rib behind subclavian groove

Scaleneus Posterior from post. tubercles of transverse processes C4-C6 to lateral superior surface of 2nd rib

Flex, rotate elevate rib

Pre-Vertebral

Longus Coli

Bodies of C5-T3 to bodies of C2-C4 Bilaterally flexes cervical v., unilaterally

rotates rotate and side bend C2-C8 innervation

Longus Capitis

Ant. Tubercles of transverse processes of C3-C6

To inferior surface of basilar portion of occipital bone

Flex, c. v. and head rotate and flex c. v.

Anterior Small Muscles

Rectus Capitis Anterior• Ant. Surface of lateral mass of the atlas to inf. Surface

of occipital bone anterior to foramen magnum

• C1 – C2

Rectus Capitis Lateralis• Sup surface of transverse process of atlas to inferior

surface of jugular process, occipital bone

• C1-C2

Both support skull

Anterior Sub Occipital Muscles

Cervical Plexus

A small plexus originating from the ventral rami of C1-C4 with some contribution from C5

Mostly cutaneous type nerves One notable somatic motor nerve = the

Phrenic nerve to the diaphragm muscle The other motor nerves work with cranial

nerves to innervate hyoid type muscles

Cervical Plexus

Cervical Plexus

Cervical Plexus

Cervical Plexus

Phrenic Nerve in Thorax

Phrenic Nerve

Cervical Plexus

Suprahyoids

Infrahyoids

Comparison