The Cavity of The Thorax

The capacity of the cavity of the thorax does not correspond with its apparent size externally, because

1.      The space enclosed by the lower ribs is occupied by some of the abdominal viscera

2.      The cavity extend above the first rib into the neck.

 

The size of the cavity of the thorax is constantly varying during life with the movements of the ribs and Diaphargm and with the degree of distention of the abdominal viscera. From the collapsed state of the lungs, as seen when the thorax is opened, in the dead body, it would appear as if the viscera only partly filled there is no vacant space, that which is seen after death being filled up by the expanded lungs.

 

The upper opening of the Thorax

The parts which pass through the upper opening of the thorax and sterno-thyroid muscles, the remains of the thymus gland, the tracheas oesophagus, thoracle duet, the inferior thyroid veins, and the longus colli musle of each side; at the sides, the innominate artery, the left common carotid and left sabelavian arteries, the internal mammary and superior intercostal arteries, the right and left innominate veins, the pneumogastric, cardiac, phrenic and sympathetic nerves, the anterior branch of the firs dorsal nerve, and the recurrent laryngeal nerve of the left side. The apex of each lung, covered by the pleura, also projects through this aperture, a little above the margin of the first rib.

 

The lower opening of the thorax is wider transversely than from before backward. It slopes obliquely downward and backward, so that the cavity of the thorax is much deeper behind than in front. The Diaphragm closes in the opening, forming the floor of the thorax. The floor is flatter at the center than at the sides, and is lighter on the right side than on the left, corresponding is the dead body to the upper border of the fifth costal cartilage on the former, and to the correspondng part of the sixth costal cartilage on the latter. From the highest point on each side the floor slopes suddenly downward to the attachment of the Diaphragm to the ribs; this is more marked behind than in front, no that only a narrow space is left between it and the wall of the thorax.