The scalenus medius muscle is the longest scalenus muscle and is counted as the cervical musculature and respiratory aid musculature. The skeletal muscle is also referred to as the middle ribs lift and increases the thorax in bilateral contraction to facilitate the forced inspiration. With the musculus scalenus anterior, the muscle forms the gap between the scalenes, which gains pathological relevance in the context of the scalene syndrome.

What is the scalenus medius muscle?

The neck muscles or ventral neck muscles consist of various skeletal muscles that contribute to the anterolateral muscle mass of the neck. Neck muscles are sometimes called the neck muscles, which are basically more of the back muscles. One of the skeletal muscles on the neck is the scalenus medius muscle.

The Latin adjective "scalenus" means something like "unequal" or "crooked" and thus already refers to the morphology of the cervical muscle. The scalenus medius muscle is better known as the medial rib cage muscle. The scalenus anterior muscle, which is also attributed to the cervical musculature and together with the scalenus medius muscle, forms the so-called scalenus gap, which is to be distinguished from the middle rib support. In total, there are three mucus scaleni. The third scalenus muscle is the scalenus posterior muscle. All three scaleni muscles are referred to as hypaxial skeletal muscles and are located in the thoracic region. Each half of the body is equipped with a central rib lifter.

Anatomy & Construction

The origins of the scalenus medius muscle correspond to the transverse processes of cervical vertebrae. More precisely, these are cervical vertebrae three to seven. Its approach takes the middle rib holder in most cases at the first or second rib. The muscle extends from here posterior to the subclavian artery and occasionally attaches to the outer surface of the ribs.

The scalenus medius muscle is the longest scalenus muscle in human anatomy. There is a free space between the middle rib support and the shorter scalenus anterior muscle, which is also called the posterior scalene gap. At this point, next to the brachial plexus, the subclavian artery passes to enter the axilla. The innervation of the scalenus medius muscle is taken over by the anterior branches of various spinal nerves. More specifically, the spinal nerves from spinal cord segments C4 to C7 are involved in the innervation of the cervical muscle.

Function & Tasks

The scalenus medius muscle makes significant contributions to the motor function of the neck. The muscle moves his neck to the side in one-sided contractions. Thus, the middle rib siphon tends the cervical spine in one-sided contraction. If the skeletal muscles contract on both sides of the body, it pulls the neck downwards. The contractions of the muscle not only affect the neck motor, but also have an impact on the general trunk motor skills.

Above all, the bilateral contraction of the skeletal muscle changes something in the morphology of the trunk and thorax. As part of the bilateral contraction, the scalenus medius muscle raises the upper ribs. This relationship has helped the muscle to qualify as a "middle rib lifter". The raised ribs automatically change the thorax. First and foremost, the bony thorax enlarges its volume through muscle contraction. Like the other two scaleni muscles, the scalenus medius muscle is one of the respiratory auxiliaries that performs important tasks in inspiration.

The scalenus anterior muscle, for example, elevates the first rib in bilateral contraction and fixed cervical spine, which also causes enlargement of the thorax. The scalenus posterior muscle promotes dilatation of the bony thorax in bilateral contraction and the scalenus medius muscle expands the bony thorax when inhaled by contracting bilaterally. As with all other components of inspiratory respiratory muscles, the scalenus medius muscle therefore supports breathing with increased or forced inspiration. The respiratory muscles should not be confused with the actual respiratory muscles, which consists of diaphragm and intercostal muscles.

Diseases

The scalenus medius muscle can acquire pathological significance in the context of different compression syndromes. The most well-known phenomenon in this context is the scale syndrome. Compression syndrome is sometimes referred to in the literature as Halsrippensyndrom or Naffziger syndrome.

This nerve compression syndrome comes from the group of thoracic outlet syndromes. The plexus brachial plexus is jammed in the phenomenon in the scalena gap between the scalenus medius and anterior muscle. Different deficits in the neurological area can be the result. Since the brachial plexus innervates the shoulder and chest muscles and is also involved in the sensitive motor innervation of the arms and hands, patients with scale syndrome often suffer from stress-related pain in the shoulder and arm area. In individual cases, the sensory innervation of the hand may be disturbed by the nerve compression. Hypesthesia and paresthesia are the result.

In some cases, the emotional disorders are associated with circulatory disorders. The latter is especially true when the subclavian artery is affected by the compression. In addition to numbness and heaviness, paralysis of the arm or chest muscles may occur. In extreme cases, it can lead to paralysis-related atrophy of the muscles, which affect in particular the small hand muscles.

The region between the scalenus anterior and medius muscles is a bottleneck for the brachial plexus, especially if the patients have additional cervical ribs. Such additional ribs are one of the most common causes of the scaling syndrome. Hypertrophic muscles can also be the cause. Hypertrophy of muscles leads to an increase by increasing the cell volume with a constant cell number. This phenomenon usually develops in the context of muscles from functional stress or hormonal stimulation.

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