Semispinalis muscle

The semispinalis muscle is an epaxial muscle of the back, included in the transversospinalis muscle complex. It is closely associated with, but lateral to the spinalis muscle. It extends vertebral column and head. 

In ruminants and carnivores, the spinalis thoracis, pinalis cervicis, semispinalis thoracis and semispinalis cervicis are associated in one muscular mass.

The semispinalis muscle is divided into different parts:

• The semispinalis thoracis muscle composed by bundles that detach form mamillary processes and course over the lateral face of semispinalis muscle to the dorsal portion of spinous processes.
• The semispinalis cervicis, that is the cranial continuation of the semispinalis thoracis
• The semispinalis capitis, that is a distinct mass of the semispinalis thoracis and cervicis. It arises between the spinalis thoracis and the longissiums thoracis, and is dividided into two parts:
  • The biventer cervicis muscle: the dorsomedial division of semispinalis capitis that originates from the thoracolumbar fascia or thoracic vertebral transverse processes, courses superficial to mutifidi muscles to insert on occipital bone.
  • The complexus muscle: the ventrolateral division of semispinalis capitis that arises from cervical vertebral articular processes and inserts lateral to the biventercervicis on occipital bone.