The thoracic skeleton (sometimes termed thoracic cage) is composed by the thoracic vertebrae, the ribs and the sternum. It encloses the thoracic cavity.
The thoracic cavity presents a cranial aperture or thoracic inlet (between the first ribs, manubrium sternal and first vertebral vertebra) and a caudal aperture or thoracic outlet (delimited by the costal arches). The thoracic cavity is bounded by the thoracic wall composed by the costal arch (formed by the cartilages of the last sternal and asternal ribs), the ribs, the intercostal spaces and the angle between the left and right costal arches. On the dorsal part of the thoracic cavity are the right and left pulmonary grooves (sulcus pulmonalis), each to the right and left of the vertebral column of the dorsal part of the lungs.