412 SPLANCHNOLOGY, OR ANATOMY OF THE VISCERA 



artery, and is, therefore, named the eparterial, which ramifies 

 through the superior lobe. The hyparterial branches are 

 given off below the pulmonary artery and hence the name. 

 Ventral and dorsal branches are given off from the main bronchi, 

 increasing in number and decreasing in size, like the branches 

 of a tree, to end in the bronchioles throughout the lobules of 

 the lung. 



The Left. Has no eparterial branch. The first hyparterial 

 branch is given off 2 inches from the bifurcation of the trachea, 

 and has the same distribution through its branches as the 

 right side. 



The right bronchus lies behind the superior cava and the 

 ascending portion of the arch of the aorta, has the vena azygos 

 major vein above and the pulmonary vessels below. The 

 left bronchus passes in front of the descending aorta, has the 

 pulmonary artery above it and the vein below. The phrenic 

 nerves pass in front of the right and left bronchus, and the 

 vagus (pneumogastric) nerves pass behind them. 



The bronchi are innervated by nerves derived from the 

 sympathetic and vagi nerves, through the pulmonary plexus. 



Their structure resembles the trachea, only that the cartilagi- 

 nous rings become thinner and are replaced by an increase in 

 the muscular coat, as they approach the terminal bronchioles. 

 The alveoli rest on a basement membrane of elastic tissue, 

 surrounded by a capillary plexus formed by the pulmonary 

 arteries and veins. 



THE ORGANS OF DIGESTION 

 THE MOUTH. ORAL OR BUCCAL CAVITY (CAVUM ORIS) 



The mouth is the upper part of the alimentary canal. It 

 is bounded by the lips, cheeks, tongue, hard and soft palate, 

 alveolar processes of both jaws, with their contained teeth, 

 and opens behind, through the isthmus faucium, into the 

 pharynx. It is lined by mucous membrane continuous in 

 front with the skin, behind with that of the fauces, its epithe- 

 lium being stratified. 



The teeth in the human subject are erupted in two sets, 

 a temporary or deciduous, or milk teeth, and a permanent 



