Auxiliary respiratory muscles
Breathing muscles (or respiratory auxiliary muscles) are various muscles from the group of skeletal muscles that help to expand or constrict the chest. In this way, these muscles make an important contribution to inhalation and exhalation. By far the most important component of the respiratory muscles is the diaphragm (lat.
diaphragm). In addition, various muscles of the chest, abdomen and back also belong to the breathing muscles group. A rough distinction is made between so-called chest breathing and abdominal breathing.
Inspiratory respiratory musculature
The most important component of the respiratory muscles during inspiration (inhalation) is the so-called diaphragm (diaphragm). For this reason, diseases of the diaphragm can also cause breath-related pain. Basically, this structure is less a real muscle than a plate consisting of muscle fibres and tendons.
The diaphragm in humans is about 3 to 5 mm thick and separates the thoracic and abdominal cavities. The diaphragm alone, as a breathing muscle, can perform between 60 and 80 percent of the muscle work required for inhalation by contracting sufficiently. For this reason, the diaphragm is considered the “motor” of so-called diaphragmatic or abdominal breathing.
In a neutral breathing position (i.e. at the end of expiration), the diaphragm takes up a position that is bulging towards the chest. At the beginning of inhalation, the muscle-tendon plate begins to shorten by up to 35 percent. In the course of this, there is a marked flattening and the formation of a cone shape.
As a result of this process and the interaction with other components of the respiratory musculature, the chest area is greatly enlarged. At the same time, the activity of the diaphragm triggers an increase in the negative pressure within the pleural gap. In addition to the diaphragm, the outer intercostal muscles (Musculi intercostales externi), the scalene muscles and the muscles in the area of the costal cartilage (Musculi intercartilaginei) are counted among the group of inspiratory respiratory muscles.
Respiratory auxiliary muscles during inhalation
Although the diaphragm is the most important respiratory muscle, the oxygen demand can often only be met with the help of the respiratory assistance muscles. This special group of respiratory muscles is mainly fixed to the bony structures of the thorax. For this reason, the individual muscles allow an enlargement of the chest area and a significant increase in the breathing volume.
In contrast to the normal respiratory musculature, the auxiliary respiratory musculature cannot be used for inhalation or exhalation support in a normal body position. The activation of this special breathing musculature requires the reversal of the attachment and origin of the muscle fibres. In order to be able to use the respiratory support muscles for support, it is usually sufficient to press the arms firmly against the thighs, a table or similar.
This group of respiratory musculature therefore plays a decisive role, especially during sports activities. It also facilitates breathing in the presence of various lung diseases. The diseases relevant in this context include water retention in the lungs (pulmonary oedema), asthma and scarring of the lung tissue (pulmonary fibrosis). The most important representatives of this group of respiratory muscles include
- The rib lifting muscles (Musculi levatores costarum),
- The anterior saw muscle (musculus serratus anterior),
- The posterior superior and posterior inferior saw muscle (musculus serratus posterior superior et inferior),
- The large and small pectoral muscle (Musculus pectoralis minor et major) and
- The muscle between sternum and mastoid (sternocleidomastoid muscle).