The longissimus muscle spans the entire back and is one of the locomotor muscles of the back. The skeletal muscle is primarily responsible for straightening the spine and consists of three distinct parts. Various malpositions are associated with the longissimus muscle, most notably lordosis.
What is the longissimus muscle?
The muscles of the back consist of different parts. In addition to the auxiliary muscles, the autochthonous back muscles should be mentioned in this context. In turn, the autochthonous back musculature includes the sacrospinal system, which is composed of the Musculus longissimus cervicis, Musculus longissimus capitis, and Musculus longissimus thoracis muscles. Together, these three muscle parts form the longissimus muscle entity. Medical literature sometimes refers to a fourth muscle part, the so-called Musculus longissimus lumborum. Other authors, however, interpret this muscle part as a part of the iliocostalis muscle. This assignment problem basically fits the localized back musculature, whose individual entities are difficult to differentiate. The longissimus muscle is also known as the erector spinae muscle, which literally means “erector of the spine”. Together with other back muscles, it forms the epaxial trunk musculature. The skeletal muscle is innervated segmentally in each case by rami posteriores of the spinal nerves.
Anatomy and structure
In humans, the longissimus muscle extends over the entire back and extends from the sacrum to the head. The skeletal muscle is located between the iliocostalis and semispinalis muscles, with which it forms the erector spinae and epaxial trunk muscles together. The longissimus muscle is located with each of its portions dorsal to the vertebral transverse processes. The portion Musculus longissimus thoracis takes its origin at the facies dorsalis at the Os sacrum. In addition, the spinous processes of the lumbar vertebrae and the transverse processes of the lower thoracic vertebrae are considered to be the region of origin. The longissimus cervicis muscle, on the other hand, originates from the transverse processes of the first to sixth thoracic vertebrae. For the longissimus capitis muscle, the transverse processes of the third cervical vertebra up to those of the third thoracic vertebra are considered to be the origin. The longissimus thoracis muscle thus attaches to the transverse processes of the thoracic and lumbar spine. In the lumbar spine, the second to twelfth ribs between the angulus costae and tuberculum costae are considered the insertion. For the longissimus cervicis muscle, the posterior tuberosity on the second to seventh cervical vertebrae is considered the insertion. For the longissimus capitis muscle, it is the mastoid process.
Function and tasks
The longissimus muscle performs various functions in the human body. All of them are motor functions that are more or less concentrated in the area of the back. Like any muscle, the longissimus muscle is to be understood as a neuromuscular unit consisting of muscle tissue and the supplying nerve structures. Ultimately, therefore, it is not possible to speak directly of the functions of the longissimus muscle. More correctly, it should read “the functions of the neuromuscular entity consisting of the musculus longissimus and rami posteriores. Since the muscle consists of three different parts, its motor functions can be divided into three parts. The Musculus longissimus thoracis muscle part is responsible for extension and lateral inclination in the thoracic as well as lumbar spine. It is also responsible for extension and dorsiflexion of the thoracic and lumbar spine, while expiration is also supported by this muscle part. The longissimus cervicis muscle has similar functions. Its contraction causes dorsiflexions as well as lateral inclinations in the cervical and thoracic spine. The longissimus capitis muscle in turn triggers dorsiflexion, rotation and lateral inclination of the head and cervical spine through its contraction. In principle, bilateral contraction of the longissimus muscle causes the spine to straighten or extend, with elevation of the neck. In contrast, unilateral contraction is responsible for the sideways inclination of the spine. The muscle receives the commands to contract from the central nervous system. On efferent pathways, the commands from the central nervous system reach the motor end plate in the form of action potentials, where they are transmitted to the muscle.Sometimes the most important symptom of lordosis is considered to be the so-called curvature of the abdomen, which in this case points in a ventral direction.
Diseases
The individual parts of the longissimus muscle, like all other muscle parts, can be affected by tension, incorrect strain, spasm, inflammation, and other muscle diseases. In addition, lesions on the supplying nerves as well as central lesions in the area of the spinal cord can cause paralysis of the muscle or its parts. Trauma, tumors, compression or inflammation may be responsible for such paralysis. In principle, diseases of the peripheral or central nervous system can also cause paralysis of the muscle. Far more often than with paralysis, however, the longissimus muscle is associated with pathological phenomena such as lordosis and scoliosis. Lordosis corresponds to a forward curvature of the spine. In scoliosis, there is a lateral deviation of the spine. These abnormal postures may be due to individual conditions of the longissimus muscle. The trigger for a hollow back in the sense of a lordosis can be, for example, inadequately trained and therefore hypertonic back muscles due to lack of exercise, which no longer relax properly. Especially in later stages, a lordosis leads to more or less severe back pain and can also promote secondary diseases such as a herniated disc or the phenomenon of slipped vertebrae. For this reason, lordosis must be prevented. Prevention measures include detonation techniques, relaxation techniques and a balanced training of back and abdominal muscles, in addition to back school.
