Dissection of thoracic and lumbosacral regions of back from a posterior approach
Multifidus and rotator muscles in mid-thoracic region
The transversospinal group of muscles includes the semispinalis, multifidus and rotator muscles that extend obliquely upward from transverse processes to spinous processes of higher vertebrae. The semispinalis muscles, in general spanning five to six vertebrae, are shown in views 213-6, 216-4 and 216-5. Parts of the semispinalis have been cut away in this dissection to expose the more deeply placed multifidus (11) and rotator (13,14) muscles. The former span three or four vertebrae whereas the latter muscles extend across only one or two vertebrae.
Serratus posterior superior muscle (insertions into fourth and fifth ribs)
Lateral costotransverse ligament
Levator costarum brevis muscle
Iliocostalis muscle (one muscle slip preserved to illustrate manner in which muscle arises medial to insertion of lower portions of muscle)
Longissimus thoracis muscle (areas of insertion on rib and transverse process)
Rib VI
Dorsal branch thoracic nerve VII
Spinous process vertebra Th. III
Semispinalis thoracis muscle (cut across and elevated)
Middle cutaneous branch of dorsal branch thoracic nerve III (note muscular branch to multifidus)
Multifidus muscle
Trapezius muscle
Rotator longus muscle
Rotator brevis muscle
External vertebral venous plexus (posterior)
Longissimus thoracis muscle (origin, elevated and cut across)