The levator scapulae is a slender

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...

situated at the back and side of the neck. As the Latin name suggests, its main function is to lift the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

Anatomy

Attachments

The muscle descends diagonally from its origin to its insertion.

Origin

The levator scapulae originates from the posterior tubercles of the

transverse processes The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

cervical vertebrae In tetrapods, cervical vertebrae (singular: 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 ...

C1-4. At its origin, it attaches via tendinous slips.

Insertion

It inserts onto the medial border of the scapula (with its site of insertion extending between the superior angle of the scapula superiorly, and the junction of

spine of scapula The spine of the scapula or scapular spine is a prominent plate of bone, which crosses obliquely the medial four-fifths of the scapula at its upper part, and separates the supra- from the infraspinatous fossa. Structure It begins at the vertica ...

and medial border of scapula inferiorly).

Relations

One of the muscles within the floor of the posterior triangle of the neck, the superior part of levator scapulae is covered by sternocleidomastoid and its inferior part by the

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 spine and laterally to the spine of the scapula. It moves the scapula and supports th ...

. It is bounded in front by the

scalenus medius The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene. They are innervated by the third to the eight cervical spinal nerves (C3-C8). The anterior and m ...

and behind by splenius cervicis. The

spinal accessory nerve The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial nerve ...

crosses laterally in the middle part of the muscle and the dorsal scapular nerve may lie deep to or pass through it. The levator scapulae may lie deep to the

sternocleidomastoid The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the access ...

at its origin, deep or adjacent to the

splenius capitis The splenius capitis () () is a broad, straplike muscle in the back of the neck. It pulls on the base of the skull from the vertebrae in the neck and upper thorax. It is involved in movements such as shaking the head. Structure It arises from th ...

at its origin and mid-portion, and deep to the

in its lower portion.

Variation

The number of attachments varies; a slip may extend to the occipital or mastoid, to the

scalene Scalene may refer to: * A scalene triangle, one in which all sides and angles are not the same. * A scalene ellipsoid, one in which the lengths of all three semi-principal axes are different * Scalene muscles of the neck * Scalene tubercle The sc ...

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 The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the r ...

corresponds to a muscle of lower animals. More or less union with the serratus anterior muscle.''

Gray's Anatomy ''Gray's Anatomy'' is a reference book of human anatomy written by Henry Gray, illustrated by Henry Vandyke Carter, and first published in London in 1858. It has gone through multiple revised editions and the current edition, the 42nd (Octo ...

'' (1918), see infobox

Innervation

The levator scapulae is innervated by 2-3 branches of the third and fourth cervical nerves, and frequently by a branch from the dorsal scapular nerve.

Blood supply

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.

Function

When the spine is fixed, levator scapulae elevates the scapula and rotates its inferior angle medially. It often works in combination with other muscles like the rhomboids and pectoralis minor to produce downward rotation of the scapula. 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 scapulae rotates to the same side 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.

Non-human animals

The muscles of the shoulder can be categorized into three topographic units: the scapulohumeral, axiohumeral, and axioscapular groups. Levator scapulae forms part of the latter group together with rhomboid major, rhomboid minor, serratus anterior, and trapezius. The trapezius evolved separately, but the other three muscles in this group evolved from the first eight or ten ribs and the transverse processes of the cervical vertebrae (homologous to the ribs). The serratus anterior formed the basal unit for these three muscles. In higher primates it has evolved into two separate muscles — serratus anterior and levator scapulae — by concentration of the proximal and distal fibers and progressive reduction of the intermediate fibers. The fibers concerned with the cranial displacement of the scapula became the levator scapulae.

Additional images

File:Levator scapulae muscle animation small2.gif, Position of levator scapulae muscle. File:Gray84.png, A cervical vertebra File:Gray85.png, Side view of a typical cervical vertebra File:Gray203.png, Left scapula. Dorsal surface. File:Gray384.png, Section of the neck at about the level of the sixth cervical vertebra. File:Gray385.png, Muscles of the neck. Lateral view. File:Gray794.png, Hypoglossal nerve, cervical plexus, and their branches. File:Gray808.png, The right brachial plexus with its short branches, viewed from in front. File:Anterior region of neck.JPG, Levator scapulae muscle File:Slide1cord.JPG, Brachial plexus. Deep dissection. File:Slide1ecc.JPG, Brachial plexus. Deep dissection. Anterolateral view

References

Sources

* * *

External links

{{Authority control Muscles of the upper limb Spine lateral flexors Spine rotators