The obliquus capitis inferior muscle () is a muscle in the upper back of the neck. It is one of the

suboccipital muscles The suboccipital muscles are a group of muscles defined by their location to the occiput. Suboccipital muscles are located below the occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput ( ...

. Its inferior attachment is at the

spinous process Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

of the

axis An axis (: axes) may refer to: Mathematics *A specific line (often a directed line) that plays an important role in some contexts. In particular: ** Coordinate axis of a coordinate system *** ''x''-axis, ''y''-axis, ''z''-axis, common names ...

; its superior attachment is at the

transverse process Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

of the

atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...

. It is innervated by the

suboccipital nerve The suboccipital nerve (first cervical dorsal ramus) is the dorsal primary ramus of the first cervical nerve (C1). It exits the spinal cord between the skull and the first cervical vertebra, the atlas. It lies within the suboccipital triangle ...

(the posterior ramus of first cervical spinal nerve). The muscle rotates the head to its side. Despite what its name suggest, it is the only capitis (Latin: "head") muscle that does not actually attach to the skull.

Anatomy

The obliquus capitis inferior is one of the

(and the only one of these to have no attachment to the skull). It is larger than the

obliquus capitis superior muscle The obliquus capitis superior muscle () is a small muscle in the upper back part of the neck. It is one of the suboccipital muscles. It attaches inferiorly at the transverse process of the atlas (first cervical vertebra); it attaches superiorly a ...

. It forms the inferolateral boundary of the

suboccipital triangle The suboccipital triangle is a region of the neck bounded by the following three muscles of the suboccipital group of muscles: * Rectus capitis posterior major - above and medially * Obliquus capitis superior - above and laterally * Obliquus capit ...

. 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

of the axis (cervical vertebra C2) (inferior to the attachment of the

rectus capitis posterior major muscle The rectus capitis posterior major (or rectus capitis posticus major) is a muscle in the upper back part of the neck. It is one of the suboccipital muscles. Its inferior attachment is at the spinous process of the axis (Second cervical vertebra); ...

) and the

lamina Lamina may refer to: People * Saa Emerson Lamina, Sierra Leonean politician * Tamba Lamina, Sierra Leonean politician and diplomat Science and technology * Planar lamina, a two-dimensional planar closed surface with mass and density, in mathem ...

of the axis. Its superior attachment is at (the inferoposterior aspect of) the

of the atlas (cervical vertebra C1).

Innervation

The muscle receives motor innervation from the

(the posterior ramus of cervical spinal nerve C1).

Relations

It lies deep to the

semispinalis capitis The semispinalis muscles are a group of three muscles belonging to the transversospinales. These are the semispinalis capitis, the semispinalis cervicis and the semispinalis thoracis. Location The semispinalis capitis (''complexus'') is situate ...

and

trapezius The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the human spine, spine and laterally to the spine of the scapula. It moves the scapula and ...

muscles.

Actions/movements

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

Function

The muscle is responsible for rotation of the head and first

cervical vertebra In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sauropsid s ...

(

atlanto-axial joint The atlanto-axial joint is a joint in the upper part of the neck between the atlas bone and the axis bone, which are the first and second cervical vertebrae. It is a pivot joint, that can start from C2 To C7. Structure The atlanto-axial joint ...

). The obliquus capitis inferior muscle, like the other suboccipital muscles, has an important role in

proprioception Proprioception ( ) is the sense of self-movement, force, and body position. Proprioception is mediated by proprioceptors, a type of sensory receptor, located within muscles, tendons, and joints. Most animals possess multiple subtypes of propri ...

. 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 The spinal column, also known as the vertebral column, spine or backbone, is the core part of the axial skeleton in vertebrates. The vertebral column is the defining and eponymous characteristic of the vertebrate. The spinal column is a segmente ...

occipital bone The occipital bone () is a neurocranium, cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lob ...

and obliquus capitis inferior muscle. The muscle arises from the apex of the

of the

and insert into the lower and back part of the

of the

. File:Suboccipital triangle dissection.jpg, Obliquus capitis inferior's relationship to other suboccipital muscles.

References

External links

{{Authority control Muscles of the head and neck