kylkivälilihas

The term "kylkivälilihas" refers to the intercostal muscles located in the thoracic region of the body. These muscles are crucial for the mechanics of breathing. They are situated between the ribs, hence their name, which translates from Finnish as "rib-between-muscle." There are two main sets of intercostal muscles: the external intercostals and the internal intercostals.

The external intercostal muscles are primarily involved in inhalation. When they contract, they pull the ribs upward and outward, increasing the volume of the thoracic cavity. This expansion creates a lower pressure within the lungs compared to the external atmosphere, causing air to rush in.

The internal intercostal muscles, on the other hand, are mainly involved in forced exhalation. Their contraction pulls the ribs downward and inward, decreasing the volume of the thoracic cavity and forcing air out of the lungs more forcefully. During quiet breathing, exhalation is largely a passive process driven by the elastic recoil of the lungs and chest wall, with the internal intercostals playing a lesser role.

These muscles work in coordination with the diaphragm, another primary respiratory muscle, to facilitate the continuous process of breathing, which is essential for oxygen intake and carbon dioxide removal.