Transversus thoracis muscle 2338453 162305817 2007-10-04T19:37:01Z Jerome Charles Potts 562899 corrected link for "xiphoid process" {{Infobox Muscle | Name = {{PAGENAME}} | Latin = musculus transversus thoracis | GraySubject = 117 | GrayPage = 403 | Image = Transversus thoracis.png | Caption = Posterior surface of sternum and costal cartilages, showing Transversus thoracis. | Origin = [[costal cartilages]] of last 3-4 ribs, body of sternum, xiphoid process | Insertion = [[ribs]]/[[costal cartilages]] 2-6 | Blood = [[intercostal arteries]]/veins | Nerve = [[intercostal nerves]] | Action = depresses ribs | MeshName = | MeshNumber = | DorlandsPre = m_22 | DorlandsSuf = 12551274 | }} The '''tranversus thoracis''' lies internal to the [[thoracic cage]], anteriorly. It is a thin plane of muscular and tendinous fibers, situated upon the inner surface of the front wall of the chest. It is in the same layer as the [[subcostal muscles]]. It arises on either side from the lower third of the posterior surface of the body of the [[sternum]], from the posterior surface of the [[xiphoid process]], and from the sternal ends of the [[costal cartilages]] of the lower three or four true ribs. Its fibers diverge upward and lateralward, to be inserted by slips into the lower borders and inner surfaces of the costal cartilages of the second, third, fourth, fifth, and sixth ribs. The lowest fibers of this muscle are horizontal in their direction, and are continuous with those of the [[Transversus abdominis]]; the intermediate fibers are oblique, while the highest are almost vertical. This muscle varies in its attachments, not only in different subjects, but on opposite sides of the same subject. ==Nerve supply== It is supplied by [[ventral rami]] of intercostal nerves. ==Function== It is almost completely without function, but it separates the thoracic cage from the [[parietal pleura]]. Contraction of this muscle aids in exertional expiration by decreasing the transverse diameter of the thoracic cage. ==Additional images== <gallery> Image:Gray503.png|Transverse section of thorax, showing relations of pulmonary artery. Image:Gray819.png|Diagram of the course and branches of a typical intercostal nerve. </gallery> ==External links== * {{MuscleLoyola|tth}} * {{eMedicineDictionary|Transversus+thoracis+muscle}} * {{SUNYAnatomyLabs|18|05|01|04}} - "Thoracic Wall: Removal of Intercostal Muscles" * {{NormanAnatomy|thoraxmuscles}} {{Gray's}} {{muscle-stub}} {{Muscles of trunk}} [[Category:Muscles of the trunk]] [[de:Musculus transversus thoracis]] [[ja:胸横筋]]