Trapezius Muscle: Structure, Function & Diseases

The trapezius muscle, or trapezius muscle, is also known as the hood muscle because of its location and anatomical shape. It consists of three parts in total.

What is the trapezius muscle?

The trapezius muscle (Musculus trapezius) is located in the area of the neck and upper back. It is divided into three different sections, each of which performs a different function. Paralysis of the trapezius muscle causes shoulder misalignment and pain. Various movements are also no longer possible when the trapezius muscle is paralyzed.

Anatomy and structure

In humans, the trapezius muscle consists of three parts. The descending part (pars descendens) is located above the scapula. This part of the trapezius muscle takes its origin from the occipital bone (Os occipitale) and the nuchal ligament. The nuchal ligament is a paired ligament that runs from the occipital bone to the spinous process of the seventh cervical vertebra. The upper cervical vertebrae also serve as the point of origin for the pars descendens of the trapezius muscle. The insertion of this part of the muscle is located in the lateral third of the clavicle. The pars transversa, the transverse part of the trapezius muscle, is located between the thoracic vertebrae and is called the middle hood muscle. Origin is the seventh cervical vertebra and the first three vertebrae of the thoracic spine. Muscle insertion is the acromion. The acromion is also known as the bone corner. It forms the highest point of the scapula in humans. The third part of the trapezius muscle is the pars ascendens. This ascending part lies below the scapula. The origin of the lower hood muscle is the thoracic vertebrae four to twelve. The point of attachment, on the other hand, is the spina scapulae. The spina scapulae is the shoulder bone that runs across the dorsal surface of the scapula and divides the scapula into the fossa infraspinata and fossa supraspinata. Occasionally, the trapezius muscle is also fused with the sternocleidomastoid muscle. This muscle is also known as the head nodder or head turner. It is located between the sternum, clavicle and base of the skull. Both muscles develop from a common anlage and are also supplied by the same nerve (accessorius nerve). It is only through the separation of the common anlage of the muscles that the typical lateral cervical triangle (regio cervicalis lateralis) is formed.

Function and tasks

The individual subsections of the trapezius muscle have almost opposite directions of action, allowing the muscle to perform different functions. The pars descendens, the descending part, is responsible for rotating the head. Lifting the shoulders is also part of the job of this section of the muscle. The pars descendens is mainly trained during weight training and bodybuilding. A well-trained descending part of the trapezius muscle results in the shoulders remaining stable and not dropping even when carrying heavy loads. A contraction of the middle hood muscle (pars transversa) leads to a contraction of the shoulders due to the contraction of the shoulder blades. The pars ascendens, which is the ascending part of the trapezius muscle, lowers the shoulders. Elevation of the trunk with the arms fixed is also possible thanks to the ascending trapezius muscle.

Diseases

Pain in the neck and upper back is often due to tension in the trapezius muscle. The most common cause of this tension is prolonged sitting in unergonomic postures. Impairment of the trapezius muscle is particularly common in people who work a lot at a computer or sit frequently at a desk. An unfavorable sleeping position, incorrect posture and heavy strain during sports can also lead to tension in the area of the trapezius muscle. It is not uncommon for tension and muscle stiffness to be caused by psychological stress and psychosomatic factors. Another risk factor for tension in the trapezius muscle is shoulder bags. People who carry bags on one side of the shoulder often pull the affected shoulder up so that the strap of the bag does not slip off the shoulder. This causes one half of the pars descendens to work permanently, so tension can quickly develop. Impairment of the trapezius muscle is manifested by pain in the neck, pain in the upper back and shoulder, or often headaches. The muscles tire quickly, so that lifting the arms or shoulders is only possible for a short period of time.Sooner or later, the constant tension also leads to signs of wear and tear in the cervical and thoracic spine. The vertebrae, the intervertebral joints and the intervertebral discs are particularly affected. A possible consequence is the acute or chronic neck-arm or shoulder-arm syndrome. In the vernacular, these phenomena are also known as lumbago. If the impairment of the trapezius muscle appears as neck-head syndrome, symptoms such as dizziness, flickering eyes and ringing in the ears are also possible. More rarely, the so-called cervical cord syndrome develops. Here, due to degenerative changes resulting from tension in the trapezius muscle, the intervertebral disc in the cervical spine bulges. As a result, the spinal canal is narrowed and the cervical medulla is squeezed. Acute contusion can lead to paralysis of the arms and legs. However, it is rather rare. More often, the damage develops more slowly. Gait disturbances, tingling and disturbances of fine motor movements are typical. When the trapezius muscle is paralyzed by a disease, this paralysis is manifested by a depression of the diseased shoulder. The middle edge of the shoulder blade is crooked and points downward from the top outside to the inside. If the arm is to be lifted sideways, this is only possible for a small section. Lifting to the horizontal is not possible. The hold of the scapula on the spine is also severely impaired.