Levator scapulae muscle
Encyclopedia
In human anatomy, the levator scapulae is a skeletal muscle
situated at the back and side of the neck. As the name suggests, its main function is to lift the scapula
.
s of the transverse processes of cervical vertebrae
one to four. The muscle is inserted on the superior angle
and adjacent medial border
of the scapula.
The levator scapulae may lie deep to the sternocleidomastoideus at its origin, deep or adjacent to the splenius capitis at its origin and mid-portion, and deep to the trapezius in its lower portion.
medially. It often works in combination with other muscles like the rhomboids
and pectoralis minor to rotate down like this.
Elevating or rotating one shoulder at a time would require muscles to stabilize the cervical spine and keep it immobile so it does not flex or rotate. Elevating both at once with equal amounts of pull on both side of cervical spinal origins would counteract these forces. Downward rotation would be prevented by co-contraction of other muscles that elevate the spine, the upper fibers of the trapezius, which is an upward rotator.
When the shoulder is fixed, levator scapula rotates and flexes the cervical spine laterally. When both shoulders are fixed, a simultaneous co-contraction of both levator scapulae muscles in equal amounts would not produce lateral flexion or rotation, and may produce straight flexion or extension of the cervical spine. Which would happen is unknown.
, the superior part of levator scapula is covered by sternocleidomastoid
and its inferior part by the trapezius
.
It is bounded in front by the scalenus medius
and behind by splenius cervicis. The spinal accessory nerve crosses laterally in the middle part of the muscle and the dorsal scapular nerve
may lie deep to or pass through it.
or serratus anterior, or to the first or second rib. The muscle may be subdivided into several distinct parts from origin to insertion. Levator claviculæ from the transverse processes of one or two upper cervical vertebræ to the outer end of the clavicle corresponds to a muscle of lower animals. More or less union with the serratus anterior.
, and frequently by a branch from the dorsal scapular
.
The levator scapulae is supplied by the dorsal scapular artery
. Normally, this artery has a small branch which passes laterally to the supraspinatus fossa
of the scapula, and in a third of cases, this branch supplies the muscle. If the dorsal scapular artery comes off the transverse cervical artery, the parent transverse cervical artery splits, the dorsal scapular artery passes medially, while the transverse cervical artery passes laterally.
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
situated at the back and side of the neck. As the name suggests, its main function is to lift the scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
.
Origin and insertion
Levator scapulae originates from the dorsal tubercleTubercle
A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....
s of the transverse processes of cervical vertebrae
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...
one to four. The muscle is inserted on the superior angle
Superior angle of scapula
The superior angle of the scapula , formed by the junction of the superior and vertebral borders, is thin, smooth, rounded, inclined somewhat lateralward, and gives attachment to a few fibers of the Levator scapulae....
and adjacent medial border
Medial border of scapula
The medial border of the scapula is the longest of the three borders, and extends from the medial to the inferior angle....
of the scapula.
The levator scapulae may lie deep to the sternocleidomastoideus at its origin, deep or adjacent to the splenius capitis at its origin and mid-portion, and deep to the trapezius in its lower portion.
Actions
When the spine is fixed, levator scapulae elevates the scapula and rotates its inferior angleInferior angle of the scapula
The inferior angle of the scapula , thick and rough, is formed by the union of the vertebral and axillary borders; its dorsal surface affords attachment to the Teres major and frequently to a few fibers of the Latissimus dorsi....
medially. It often works in combination with other muscles like the rhomboids
Rhomboids
Rhomboids can refer to:* Rhomboid muscles** Rhomboid major muscle** Rhomboid minor muscle...
and pectoralis minor to rotate down like this.
Elevating or rotating one shoulder at a time would require muscles to stabilize the cervical spine and keep it immobile so it does not flex or rotate. Elevating both at once with equal amounts of pull on both side of cervical spinal origins would counteract these forces. Downward rotation would be prevented by co-contraction of other muscles that elevate the spine, the upper fibers of the trapezius, which is an upward rotator.
When the shoulder is fixed, levator scapula rotates and flexes the cervical spine laterally. When both shoulders are fixed, a simultaneous co-contraction of both levator scapulae muscles in equal amounts would not produce lateral flexion or rotation, and may produce straight flexion or extension of the cervical spine. Which would happen is unknown.
Relations
One of the muscles within the floor of the posterior triangle of the neckPosterior triangle of the neck
-Boundaries:It has the following boundaries:Apex: Union of the sternocleidomastoid and the trapezius muscles at the superior nuchal line of the occipital boneAnterior: Posterior border of the sternocleidomastoideus...
, the superior part of levator scapula is covered by sternocleidomastoid
Sternocleidomastoid muscle
In human anatomy, the sternocleidomastoid muscle , also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial layers of the anterior portion of the neck...
and its inferior part by the trapezius
Trapezius muscle
In human anatomy, the trapezius is a large superficial muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae and laterally to the spine of the scapula...
.
It is bounded in front by the scalenus medius
Scalenus medius
The Scalenus medius, the largest and longest of the three scalene muscles, arises from the posterior tubercles of the transverse processes of the lower six cervical vertebræ. It descendes along the side of the vertebral column to insert by a broad attachment into the upper surface of the first...
and behind by splenius cervicis. The spinal accessory nerve crosses laterally in the middle part of the muscle and the dorsal scapular nerve
Dorsal scapular nerve
The dorsal scapular nerve arises from the brachial plexus, usually from the plexus root of C5.It provides motor innervation to the rhomboid muscles, which pull the scapula towards the spine and levator scapulae muscle, which elevates the scapula....
may lie deep to or pass through it.
Variations
The number of vertebral attachments varies; a slip may extend to the occipital or mastoid, to the trapezius, scaleneScalene
Scalene may refer to:* A scalene triangle, one in which all sides are different* A scalene ellipsoid, one in which the lengths of all three semi-principal axes are different* Scalene muscles of the neck...
or serratus anterior, or to the first or second rib. The muscle may be subdivided into several distinct parts from origin to insertion. Levator claviculæ from the transverse processes of one or two upper cervical vertebræ to the outer end of the clavicle corresponds to a muscle of lower animals. More or less union with the serratus anterior.
Innervation and blood supply
The levator scapulae are supplied by two or three branches of the fourth and fifth cervical nervesCervical nerves
The cervical nerves are the spinal nerves from the cervical vertebrae.Although there are seven cervical vertebrae , there are eight cervical nerves . All nerves except C8 emerge above their corresponding vertebrae, while the C8 nerve emerges below the C7 vertebra...
, and frequently by a branch from the dorsal scapular
Dorsal scapular nerve
The dorsal scapular nerve arises from the brachial plexus, usually from the plexus root of C5.It provides motor innervation to the rhomboid muscles, which pull the scapula towards the spine and levator scapulae muscle, which elevates the scapula....
.
The levator scapulae is supplied by the dorsal scapular artery
Dorsal scapular artery
The dorsal scapular artery is a blood vessel which supplies thelevator scapulae, rhomboids, and trapezius.-Origin:...
. Normally, this artery has a small branch which passes laterally to the supraspinatus fossa
Supraspinatous fossa
The supraspinatous fossa of the posterior aspect of the scapula is smaller than the infraspinatous fossa, concave, smooth, and broader at its vertebral than at its humeral end. Its medial two-thirds give origin to the Supraspinatus....
of the scapula, and in a third of cases, this branch supplies the muscle. If the dorsal scapular artery comes off the transverse cervical artery, the parent transverse cervical artery splits, the dorsal scapular artery passes medially, while the transverse cervical artery passes laterally.