232 ANATOMY IN A NUTSHELL. 



183. Give relation of anterior tibial artery. 



184. Give relation of posterior tibial artery. 



185. Give relation of peroneal artery. 



186. Give relations of dorsalis pedis artery. 



LESSON LXIII. 

 The Thorax. (Plate XC1V.) 



The thorax is formed by thirty-seven bones, namely, the twenty-four ribs 

 the twelve dorsal vertebrae, and the sternum. The thorax is a conical cavity, 

 broad below, narrow above, flattened from before backward, and longest pos- 

 teriorly. Its posterior boundary is formed by the bodies of the dorsal ver- 

 tebrae and the posterior portion of the ribs, thus making it concave verti- 

 cally with a high ridges on either side. The lateral boundaries are convex, 

 being formed by the ribs and Intercostal muscles. The anterior boundary, 

 which slopes down and forward, is formed by the sternum and the costal car- 

 tilages. 



The upper opening of the thorax is broadest transversely and is formed by 

 the first dorsal vertebra posteriorly, first ribs laterally, and the upper margin 

 of the manubrium anteriorly. The upper border of the manubrium is on a 

 level with the second dorsal vertebra. In the female the sternum is shorter 

 than in the male, the ribs more movable, and the thorax is smaller. The upper 

 margin of the manubrium is on a lower level than in the male. There are forty 

 structures passing through the superior opening of the thorax. There are 

 three pairs of muscles that pass through this upper opening in the thorax. 

 Sterno-thyroid, Sterno-hyoid and Longus colli muscles, making six muscles. 

 The arteries that pass through the superior opening of the thorax are the (1) 

 innominate, (2) left common carotid and (3) left subclavian, (4) and (5) the two 

 internal mammary and (6) and (7) the two superior intercostal. There are 

 fifteen nerves that pass through this opening: (1) and (2) the two Pneumo- 

 gastric, (3) and (4) the two phrenic, the six cardiac and the two sympathetic 

 nerves, the anterior branches of the two first dorsal nerves, and the recurrent 

 laryngeal nerve of the left side make fifteen. The veins that pass through this 

 superior opening are the right and left innominate and the inferior thyroid 

 veins, making four veins. There are eight unclassified structures that pass 

 through this opening in the thorax: Remains of thymus gland, trachea, oesoph- 

 agus, thoracic duct, apex of each lung, and pleurae. Then the six muscles, 

 fifteen nerves, seven arteries, four veins, and eight unclassified structures make 

 the forty structures which pass through the superior opening of the thorax. 



The Lower opening of the thorax is widest transversely and slopes down- 

 ward and backward. It is formed by the last dorsal vertebra posteriorly, and 

 the seventh to the eleventh costal cartilages laterally, and the ensiform car- 

 tilage anteriorly. The Diaphragm separates the thoracic cavity from the 

 abdominal cavity. 



