External intercostal muscle

The **external intercostal muscle** is one of the three layers of muscles located between the ribs, forming part of the thoracic wall. There are eleven pairs on each side, originating from the lower border of one rib and inserting onto the upper border of the rib below. The fibers run obliquely downward and forward. These muscles are innervated by intercostal nerves (T1–T11) and supplied by anterior and posterior intercostal arteries[1][4][5][7]. Their primary function is to elevate the ribs during forced inhalation, thereby expanding the thoracic cavity and facilitating air entry into the lungs[1][5][6]. They are considered accessory respiratory muscles rather than molecular drug targets or receptors. **Note:** "External intercostal muscle fibers" refers to a gross anatomical structure composed primarily of skeletal muscle tissue; it is not a molecular target such as a receptor, enzyme, transporter, or ion channel. Therefore, it does not fit standard definitions for therapeutic targets in pharmacology or drug development[1][4].

Other names

External intercostalsMusculus intercostalis externus (Latin)Intercostales externi