Understanding of the extrathoracic muscle mass of the chest wall is an critical a part of the armamentarium of the overall thoracic doctor. those muscular tissues are mainly critical from an anatomic and surgical reconstructive factor of view. a thorough expertise of the extrathoracic muscle flaps is a prerequisite within the schooling of any cardiothoracic medical professional.There are five muscle tissues that make up the thoracic cage; the intercostals (external, internal and innermost), subcostals, and transversus thoracis. those muscle mass act to change the extent of the thoracic cavity throughout respiratory.There are a few different muscles that do not incorporate the thoracic wall, however do attach to it. those include the pectoralis essential, minor, serratus anterior and the scalene muscle tissues.The intercostal muscles lie within the intercostal areas among ribs. they're organised into 3 layers.inner Intercostals,these flat muscle groups lie deep to the external intercostals. just like the external intercostals, they run from the rib above to the only beneath, but in an opposite route (inferoposteriorly). they are continuous with the internal oblique muscle of the stomach wall.Transversus Thoracis these muscle tissues of the thoracic cage are non-stop with transversus abdominis inferiorly.The subcostal muscular tissues are determined inside the inferior part of the thoracic wall.