Dalley, 10th Edition

121

Muscles of Back

Mastoid process

Nuchal ligament

Transverse process of C4 Angles of ribs ( dashed line )

Longissimus capitis

Spinalis cervicis

2

Iliocostalis cervicis

Spinous process of T1

Longissimus thoracis

Iliocostalis thoracis

Spinalis thoracis

Longissimus

Spinalis

Iliocostalis lumborum

Spinous process of L2

Iliocostalis

(C) Posterior view

Iliac crest

Rotatores

Multifidus

Transversospinalis

Posterior superior iliac spine

Semispinalis

Transverse process

Thoracic spinous process

Spinalis

Erector spinae

Longissimus Iliocostalis

(A) Posterior view

(B) Posterior view

Serratus posterior inferior Angle of rib

Key for D: Back muscles

Superficial extrinsic Intermediate extrinsic

Latissimus dorsi

Intermediate intrinsic (erector spinae) Deep intrinsic (transversospinales)

Trapezius

(D) Transverse section

FIGURE 2.35. Intermediate layer of intrinsic back muscles (erector spinae muscles).

TABLE 2.6. INTERMEDIATE LAYER OF INTRINSIC BACK MUSCLES Muscle Proximal Attachment Distal Attachment

Nerve Supply Main Action(s)

Erector spinae Iliocostalis

Posterior rami of spinal nerves

Acting bilaterally: extend verte bral column and head; as back is exed, control movement via eccentric contraction Acting unilaterally: laterally exes vertebral column

Iliocostalis: lumborum, thoracis, cervicis; bers run superiorly to angles of lower ribs and cervical transverse processes. Longissimus: thoracis, cervicis, capitis; bers run superiorly to ribs between tuber cles and angles to transverse processes in thoracic and cervical regions and to mastoid process of temporal bone. Spinalis: thoracis, cervicis, capitis; bers run superiorly to spinous processes in the upper thoracic region and to cranium.

Arises by a broad tendon from the posterior part of the iliac crest, posterior surface of the sacrum, sacroiliac ligaments, sacral and inferior lumbar spinous processes, and supraspinous ligament

Longissimus

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Spinalis

The semispinalis is the super cial member of the group. As its name indicates, it arises from approximately half of the vertebral column. It is divided into three parts according to the superior attachments (Table 2.7): semispinalis capitis , semispinalis thoracis , and semispinalis cervicis . Semi spinalis capitis forms the longitudinal bulge in the back of the neck near the median plane (Fig. 2.37A).

The multi dus is the middle layer of the group and con sists of short, triangular muscular bundles that are thickest in the lumbar region (Fig. 2.37B). The rotatores , or rotator muscles, are the deepest of the three layers of transversospinal muscles and are best devel oped in the thoracic region. The transversospinalis group of the deep layer of intrinsic back muscles is illustrated