ABSTRACT
THE SKELETON of the thorax (2.2) is covered superficially by the pectoral girdle and its attached muscles (4.2, 4.3), with the overlying breasts at the front. The intercostal spaces (between adjacent ribs and costal cartilages, and numbered from the rib below which they lie) are filled in by three layers of thin intercostal muscles (5.1), with the main intercostal vessels and nerves running between the middle and inner layers along the lower border of each rib. The diaphragm, with the liver immediately
below it, b u l g e s u p w a r d s from the abdomen to a level (viewed
from the front) as high as the fifth rib and costal cartilage on the right and the fifth intercostal space on the left (4.1). The gap between the upper border of T1 vertebra, the two first ribs and costal cartilages, and the upper border of the manubrium of the sternum is the thoracic inlet (although sometimes also known as the thoracic outlet); through it pass the trachea and oesophagus, phrenic and vagus nerves, and the sympathetic trunks, great vessels of the neck, and the thoracic duct on the left.
