The obliquus capitis inferior muscle () is a muscle in the upper back of the neck. It is one of the
suboccipital muscles. Its inferior attachment is at the
spinous process 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
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
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
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 (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
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 spinous process 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 ...
and insert into the lower and back part of 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 ...
.
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