Obliquus capitis inferior muscle

Anatomy

The obliquus capitis inferior is one of the suboccipital muscles (and the only one of these to have no attachment to the skull). It is larger than the obliquus capitis superior muscle. It forms the inferolateral boundary of the suboccipital triangle.

The muscle extends laterally and somewhat superiorly from its inferior attachment to its superior attachment.

Attachments

its inferior attachment is at the lateral external aspect of the bifid spinous process of the axis (cervical vertebra C2) (inferior to the attachment of the rectus capitis posterior major muscle) and the lamina of the axis.

Its superior attachment is at (the inferoposterior aspect of) the transverse process of the atlas (cervical vertebra C1).

Innervation

The muscle receives motor innervation from the suboccipital nerve (the posterior ramus of cervical spinal nerve C1).

Relations

It lies deep to the semispinalis capitis and trapezius muscles.

Actions/movements

The muscle acts to rotate the atlas (and thus the head) ipsilaterally. It acts together with the rectus capitis posterior major muscle.

Function

The muscle is responsible for rotation of the head and first cervical vertebra (atlanto-axial joint).

The obliquus capitis inferior muscle, like the other suboccipital muscles, has an important role in proprioception. This muscle has a very high density of Golgi organs and muscle spindles which accounts for this. It is believed that proprioception may be the primary role of the inferior oblique (and indeed the other suboccipital muscles), allowing accurate positioning of the head on the neck.

Additional images

File:Obliquus capitis inferior muscle animation small.gif|Position of obliquus capitis inferior muscle (shown in red). File:Obliquus capitis inferior muscle closeup animation small.gif|Close up. Vertebral column, occipital bone and obliquus capitis inferior muscle. The muscle arises from the apex of the spinous process of the axis and insert into the lower and back part of the transverse process of the atlas. File:Suboccipital triangle dissection.jpg|Obliquus capitis inferior's relationship to other suboccipital muscles.

References

References

1. (2017). "Essential Clinical Anatomy". Lippincott Williams & Wilkins.
2. Standring, Susan. (2020). "Gray's Anatomy: The Anatomical Basis of Clinical Practice".
3. Sinnatamby, Chummy S.. (2011). "Last's Anatomy". Elsevier Australia.
4. V, Kulkarni. (2001-10-01). "Quantitative study of muscle spindles in suboccipital muscles of human foetuses.". Neurology India.