Hello again, everyone. It’s Matt from Kenhub! And in this tutorial, we will discuss the origin, insertion, innervation, and function of the intercostal muscles.
The intercostal muscles are a group of intrinsic chest wall muscles occupying the intercostal spaces. The intercostal muscles consist of the external intercostal muscles which course from the lower border of a rib ventrocaudally to the upper border of the rib below.
Ventrally, they are bordered by the external thoracic facscia.
The internal intercostal muscles originate at the upper border of a rib and insert ventrocranially at the lower border of the rib above.
The last group are the innermost intercostal muscles which separate from the internal intercostal muscles and insert behind the costal grooves. Inwards, they are bordered by the internal thoracic fascia.
The fibrous space between the internal and innermost intercostal muscles and the lower border of the rib above forms the intercostal tunnel. These tunnels provide passage for the intercostal arteries, veins, and the intercostal nerves which supply the intercostals and arise from the thoracic nerves.
The task of the intercostal muscles is to tense the intercostal spaces during deep inspiration and support the breathing mechanism. The contraction of the external intercostal muscles causes an elevation of the ribs, functioning as inspiratory breathing muscles…
Whereas both the internal and innermost intercostal muscles lower the ribs, functioning as expiratory breathing muscles.