LONG DORSI: CHARACTERISTICS, FUNCTIONS, RELATED DISORDERS - ANATOMY AND PHYSIOLOGY - 2024

The long dorsal, also known as longissimo, is a paired muscle located at the back of the trunk, on each side of the spine. It is part of the muscular complex called the erector spine.

Together with the spinous and iliocostal muscles, it fulfills the function of keeping the spine upright, as well as making lateral movements of the spine. Of the muscles that make up the erector spine, the long or very long dorsal is the one with the greatest length, hence its name. It extends from the cranial area to the sacrum.

Posterior view of the trunk, where the location and shape of the long or very long dorsal muscle are represented. Image source: https://es.m.wikipedia.org/wiki/Archivo:Longissimus.png. Edited image

The loss of tone of this muscle, as well as of others that accompany it in the dorsal area, can generate a picture of dorsal kyphosis. This is characterized by an abnormal curvature of the spine. The causes are very diverse, but the main one is poor postural hygiene.

Dorsalgia or back pain in the dorsal muscles is another very common ailment in the world population.

characteristics

The long dorsi muscle is a paired muscle. It is located vertically and symmetrically on each side of the spine, on the posterior or dorsal face of the trunk. It is a strong, thin and flat muscle, although it is thinner at the top (ends in the shape of a lance or point) and thicker in the caudal part (almost square).

The muscle consists of a belly from which emanate between 8 to 10 handfuls of ascending and external fibers and between 12 or 13 stronger and internal ones.

It has a great length, hence some authors call it very long or very long of the back. It is divided into three important areas, which are:

- Cranial dorsal longus muscle, also called by other authors as complexo minor or muscle longus of the head.

- Cervical long dorsal muscle, also called the longis muscle of the neck.

- Long thoracic dorsal muscle or thoracic longis dorsal muscle.

The long dorsi muscle is part of the muscle complex called the erector spine muscle.

The muscle has a tendinous part, specifically in the insertions at the level of the transverse processes and also of the ribs. Whereas, in its lower and posterior zone it is aponeurotic, while the body of the muscle in general is fleshy.

Origin

The long dorsi muscle extends from the sacrum to the cranial area. Its fibers go in an upward direction. As it has a considerable extension, its fascicles originate from various anatomical sites.

Some emerge from the dorsal sacroiliac ligaments, others originate from the crest of the sacrum, and finally there is a group of fascicles that come from the medial area of ​​the connective tissue that separates the muscles of the spine, called the lumbosacral fascia.

Insertion

Like its origin, as it ascends, its fascicles are inserted into different anatomical structures. From bottom to top, insertion occurs as follows:

The dorsal portion attaches to the transverse processes of the dorsal and lumbar vertebrae, as well as the lower edges of the last 7-8 ribs.

The cervical portion, as its name indicates, is attached to the transverse processes of the corresponding vertebrae (cervical), and finally the cranial portion has as its insertion site the mastoid process of the temporal bone.

Innervation

This muscle is innervated by dorsal branches corresponding to the spinal or spinal nerves, specifically the lower cervical, dorsal or thoracic and lumbar nerves.

Irrigation

As the long or long dorsal muscle is extremely extensive, encompassing the cranial, cervical, dorsal and sacral areas, this muscle receives blood nutrition from various vessels, depending on the area.

In this sense, the cervical area is nourished by the superficial and deep descending branches of the occipital artery, as well as the transverse cervical artery, the deep cervical artery, and the vertebral artery.

Meanwhile, the dorsal area reaches dorsal branches of the superior, posterior and subcostal intercostal arteries.

Whereas, the lumbosacral area is supplied by the dorsal branches of the lateral and middle sacral arteries.

Function

This muscle can act unilaterally or bilaterally. Unilaterally it allows the rotation and inclination of the spine towards the side of the muscle that is in action.

While bilaterally it participates in maintaining the upright position of the spine.

In both functions it acts in conjunction with the spinous and iliocostal muscles.

The cranial area participates in the forward and backward flexion movement of the neck and to a lesser extent in lateral movements, that is, to one side and to the other.

Related disorders

- Dorsal kyphosis

The muscles found in the deep dorsal area are the transverse spinous, epispinous, the long dorsal, and the sacrolumbar.

In this pathology, the tonic tension of the muscles of the dorsal area, including the long dorsal muscle, is lost. Muscle weakness is reflected in loss of mechanical balance, causing the spine to stoop.

In addition, there is injury to the ligaments, as the posterior common, yellow, interspinous, and supraspinatus ligaments are stretched, while the common anterior ligament is retracted.

That is why the spinal column adopts a more prominent curvature than normal in the dorsal area of ​​the spine. It is almost always accompanied by hyperlordosis, both lumbar and cervical as compensation.

There are two types: flexible dorsal kyphosis and rigid dorsal kyphosis.

Flexible dorsal kyphosis

In this case there is no bone deformation, the patient can voluntarily bring the spine to a normal position (upright) with a little effort.

This disorder can occur due to the adoption of incorrect postures for a long time at school or at work (poor postural hygiene). There may be a morphogenetic predisposition.

However, there are other more serious causes, such as asthenia and osteoporosis are risk factors for suffering from dorsal kyphosis.

It can also occur due to trauma or other conditions, such as spinal tuberculosis or Pott's disease, among others.

Rigid or fixed kyphosis

The previous condition for a long time, without the extension of the dorsal muscles, progressively generates the loss of this movement due to voluntary effort and can even reach the point that manual straightening is impossible.

- Back pain

Back pain is defined as pain that occurs in the medial area of ​​the back. The pain can involve one or more muscles, also bones, ligaments or nerves, depending on its cause. It is a very common ailment and, at least once in their life, 80% of the world's population will suffer from back pain.

There are exercises that allow you to relax and stretch your back muscles to relieve symptoms. Among these muscles is the long dorsi.

References

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