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The Back

Scroll down to follow a complete dissection of the back or click below for direct viewing:

SUPERFICIAL TRAPEZIUS

SPINAL ACCESSORY NERVE

LATISSIMUS DORSI

TRIANGLE OF AUSCULTATION

RHOMBOIDEUS AND LEVATOR SCAPULA

SERRATUS POSTERIOR

SPLENIUS CAPITIS AND CERVICIS

ERECTOR SPINAE

ILIOCOSTALES

LONGISSIMUS

SPINALIS

SEMISPINALIS

MULTIFIDUS

ROTATORES

LEVATOR COSTORUM

INTERTRANSVERSARII

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Follow the dissection manual closely for instructions on skinning the back and observation of the superficial features of the back. Grant's manual should be referenced throughout the entire dissection.

 

FIG. 1-1 : SUPERFICIAL TRAPEZIUS (back to top)

After skinning and removing the superficial fascia, the superficial back muscles are visible. The trapezius muscle originates from the external occipital protuberance, the ligamentum nuchae, and the spinous processes of C7 and T1-T12.
The ligamentun nuchae is a strong supraspinous tendon that extends from the occipital protuberance to C7.2. The trap. m. has fibers that run in several directions:


FIG. 1-2 : SPINAL ACCESSORY NERVE (back to top)

The trap. m. needs to be reflected for access to the deeper layers of muscle. After carefully cutting along the midline as close to the origin as possible, you can reflect the trap m. superiorly, exposing the underlying structures. You can now see the spinal accessory nerve running vertically on the undersurface of the muscle. On a closer view, you can see the nerve as it runs from the sternocleidomastoid m. to its termination between fibers of the trap. m.


FIG. 1-3 : LATISSIMUS DORSI (back to top)

The latissimus dorsi m. arises from the thoracolumbar fascia of the lower back. Its superior border extends laterally from the spinous processes of T6-7 while its most lateral parts interdigitate with fibers of the external oblique inferior m. The fibers of the muscle form a broad tendon which inserts into the intertubercular fossa of the humerus.


FIG. 1-4 : TRIANGLE OF AUSCULTATION (back to top)

The triangle of auscultation is visible after removal of skin on the back. This is an anatomical space that is used by physicians to listen to sounds produced by the lungs and other thoracic organs.

The borders are:

At this location, ribs 6 and 7 and the intercostal space are free of overlying mm., making it easier for auscultation.


FIG. 1-5 : RHOMBOIDEUS & LEVATOR SCAPULA (back to top)

After reflection of the trapezius and lat. dorsi mm., the next layer of superficial muscles is exposed. This includes the rhomboid major and minor muscles and the levator scapula muscle. The rhomboid minor muscle originates from the spinous process of C7-T1 and ligamentum nuchae, and inserts on the upper 1/3rd of the verterbral border of the scapula. The rhomboid major muscle originates from the spinous process of T2-5 and inserts on the lower 2/3rds of the verterbral border of the scapula. The levator scapula muscle originates on the transverse processes of C1-4 and inserts onto the superior angle of the scapula.


FIG. 1-6 : SERRATUS POSTERIOR (back to top)

The intermediate muscle group consists of the Serratus Posterior Superior and Inferior mm. These muscles are paper thin therefore caution must be used when dissecting these muscles. The serr. post. inf. m. is seen upon reflection of the lat. dorsi m. from its origin along the spine. It originates from the spinous processes of T11-L2 and inserts on the inferior borders of ribs 8-12 near their angles. The serr. post. sup. m. is located deep to the rhomboid mm. This muscle is found after careful detachment of the rhomboid mm. from their origin. The serr. post. sup. arises from the ligamentum nuchae & spinous processes of C7-T3 and inserts onto the superior borders of ribs 2-4.


FIG. 1-7 : SPLENIUS CAPITIS AND CERVICIS (back to top)

After removal of the trap. m., splenius capitis and cervicis mm. are exposed. The splenius mm. originates at the spinous processes of C7-T3. Splenius capitis inserts into the nuchal line on the occipital bone and the mastoid process of temporal bone. Splenius cervicis inserts into the posterior tubercles of transverse process of C1-C3(C4).


FIG. 1-8 : ERECTOR SPINAE (back to top)

The first layer of deep muscles in the back consist of long vertically oriented muscle bundles running down both sides of the back from the occipital bone to the pelvis. The erector spinae mm. include:


FIG. 1-9 : ILIOCOSTALES (back to top)

The iliocostales m. consists of three parts: lumbar, thoracic, and cervical.


FIG. 1-10 : LONGISSIMUS (back to top)

The different segments of the longissimus m. have a common origin on the transverse processes of the thoracic and cervical vertebrae.



FIG. 1-11 : SPINALIS (back to top)

The spinalis m. is a relatively thin mm. (about 2cm) that connects to the lumbar, thoracic, and cervical spinous processes.


FIG. 1-12 : SEMISPINALIS (back to top)

After removal of the first deep layer of back mm., the erector spinae, the Transversospinalis m. group can be dissected out. Follow Grant's dissector manual carefully, as these mm. are difficult to dissect.

The semispinalis m. is comprised of three divisions.


FIG. 1-13 : MULTIFIDUS (back to top)

After reflecting the semispinalis m., the multifidus m. can be dissected out. This muscle consists of many short bundles which are the most prominent in the lumbar region.

Its many origins include:

Its insertion is into the spinous process of the vertebrae TWO to FOUR LEVELS ABOVE THE LEVEL OF ORIGIN.


FIG. 1-14 : ROTATORES (back to top)

The deepest layer of the transversospinalis m. group is the rotatores m. These mm. originate on the transverse process of one thoracic vertebrae and insert on the base of the spinous process of the vertebrae ONE to TWO LEVELS ABOVE THE LEVEL OF ORIGIN.


FIG. 1-14 : LEVATOR COSTORUM (back to top)

The levator costorum mm. can be seen lateral to the transverse process of the vertebrae, running inferolateral in between the ribs. The origin is the transverse process of C7-T11. They insert between the tubercle and the angle on the outer surface of the ribs below the vertebrae of origin.


FIG. 1-15: INTERTRANSVERSARII (back to top)

The intertransversarii mm. are deep back muscles that bend the spinal column laterally. They are usually poorly developed in the thoracic region. The origin and insertions of this muscle is between the transverse processes of cervical, throacic and lumbar vertebrae.


JOINTS OF THE BACK

Although we will not show dissected joints of the back, it is important to understand all relevant anatomical components. Click here for labeled diagrams and descriptions of the joints adapted from Grant's Atlas.

 

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Highlighted Back Structures in Review

To view, click on the desired structure below:

SUPERFICIAL TRAPEZIUS

SPINAL ACCESSORY NERVE

LATISSIMUS DORSI

TRIANGLE OF AUSCULTATION

RHOMBOIDEUS AND LEVATOR SCAPULA

SERRATUS POSTERIOR

SPLENIUS CAPITIS AND CERVICIS

ERECTOR SPINAE

ILIOCOSTALES

LONGISSIMUS

SPINALIS

SEMISPINALIS

MULTIFIDUS

ROTATORES

LEVATOR COSTORUM

INTERTRANSVERSARII

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This page created by Don Martin, Elizabeth Taibe, Katie Jablonski. © 2003, Stephen P. Lahr
The text has been adapted from Grant's Dissector, 12th edition
Maintained by Stephen Lahr. Last updated: 3/27/03