The musculi intercostales are a special muscle section in the human body. The musculi intercostales belong to the so-called autochthonous chest muscles. They are composed of different muscle parts, which together play an important role in breathing. The most important elements of the musculi intercostales are the musculi intercostales interni, the musculi intercostales externi, and the musculi intercostales intimi.
What are the musculi intercostales?
Essentially, the musculi intercostales are composed of three parts. These parts are separate muscle groups, but they are closely connected and interact with each other during various tasks and movements of the body. These include, first, the musculi intercostales interni, which are part of the autochthonous chest musculature. The musculi intercostales interni represent a very deep layer within the intercostal musculature. They are covered by the Musculi intercostales externi in all intercostal spaces. Similarly, the musculi intercostales externi are an element of the autochthonous pectoral musculature. The musculi intercostales externi are located on the surface of the intercostal musculature, thus forming its upper level or layer. Finally, the musculi intercostales intimi are among the so-called skeletal muscles and are also part of the intercostal musculature.
Anatomy and structure
The musculi intercostales interni and the musculi intercostales externi are the so-called intercostal muscles. The musculi intercostales interni constitute the inner intercostal muscles, whereas the musculi intercostales externi constitute the outer intercostal muscles. The musculi intercostales interni originate from the upper edges of the second through twelfth ribs. The areas of origin of this type of muscle extend from the end of the cartilage of the ribs, located at the so-called sternum, to the angulus costae. The musculi intercostales interni run obliquely. Thus, the musculi intercostales attach to the lower edge of the rib above. Basically, the fibers of these muscles run in the same direction as the fibers of the so-called obliquus internus abdominis muscle. Near the border between bone and cartilage and the angulus costae, the intercostal nerves demarcate the musculi intercostales interni from the musculi intercostales intimi. The innervation of this muscle section is provided by the intercostal nerves from special areas of the spinal cord. The Musculi intercostales externi have their origin in the lower edge of the first to eleventh rib. The area of their origin here extends from the tuberculum costae to the junction between cartilage and bone. Between the cartilages of the ribs, the Musculi intercostales find their counterpart in the so-called Membrana intercostalis externa. Like the Musculi intercostales interni, the Musculi intercostales externi also run obliquely. Their course corresponds to that of the Musculus obliquus externus abdominis. The musculi intercostales externi attach to the upper edges of the second to twelfth ribs. The intercostal muscles are innervated by the intercostal nerve. The musculi intercostales intimi are a deep-lying muscular layer of the musculi intercostales interni. The musculi intercostales intimi separate from the musculi intercostales interni in the area between the angulus costae and the junction between bone and cartilage. The separation between the two muscle parts is represented here by the corresponding intercostal nerve and the respective intercostal artery. The musculi intercostales intimi are innervated by the intercostal nerve. In detail, innervation occurs segmentally from specific areas of the spinal cord.
Function and Tasks
The musculi intercostales perform several important tasks and functions in the muscular system. Primarily, they play a significant role in connection with the respiratory musculature. As respiratory muscles, the musculi intercostales interni are responsible for exhalation (medical term expiration). By tensing the respective intercostal space, they lower the ribs. As a result, the volume of the bony part of the thorax is reduced. In the same way, the musculi intercostales externi are part of the respiratory musculature.In a sense, they represent the antagonist to the Musculi intercostales interni, because they are responsible for inhalation (medical term inspiration). In conjunction with contractions, they tense the corresponding area of the intercostal space. In this way, they cause an increase in volume in the bony thorax. The musculi intercostales intimi are so-called rib depressors that also participate in exhalation.
Diseases
Various diseases and complaints are possible in connection with the musculi intercostales, sometimes severely limiting the quality of life of affected patients and in some cases even causing life-threatening conditions. Since the musculi intercostales play an important role in respiration, impairments in the functional capacity of the muscles have a correspondingly severe effect. This is because respiratory processes depend on the smooth functioning of the musculi intercostales. Disorders of the Musculi intercostales interni lead to problems with exhalation, while complications of the Musculi intercostales externi affect inhalation. For this reason, complaints of the musculi intercostales should be presented to a physician as soon as possible so that adequate therapy of the symptoms as well as the underlying disease can be started immediately. Because humans are uninterruptedly dependent on functional breathing, associated complaints should be taken seriously.
