CHAPTER XVII. 



BLOODVESSELS OF THE ALIMENTARY CANAL. 

 BY C. TOLDT. 



Mucous MEMBRANE OF THE ORAL CAVITY. 



THE mucous membrane of the mouth derives its supply of 

 blood from various branches of the external carotid artery, 

 the arterise labiales, buccinatoria, lingualis, transversa faciei 

 pterygo-palatina, and alveolaris superior and inferior. The 

 terminal branches of these arteries enter the submucous tissue 

 of the* oral cavity after the trunks from which they proceed 

 have become much diminished in size from giving off numerous 

 branches to the muscles, glands, and other organs, and after 

 having formed numerous anastomoses with each other and the 

 adjoining arterial vessels. After reaching the submucous tissue 

 they are distributed parallel to the surface, and by their 

 numerous anastomoses form a wide-meshed plexus, from which 

 branches extend into the connective tissue layer of the mucous 

 membrane, where they compose a close terminal network, in- 

 terlacing with the corresponding venous plexus. From this 

 finally the minute branches for the papillae are given off, the 

 capillaries of which present considerable variety in the dif- 

 ferent sections of the mucous membrane. 



The efferent vessels of the papillse discharge their blood into 

 a close-meshed venous plexus, which decussates with the above- 

 mentioned arterial plexus. The venous portion of the vascular 

 expansion contained in the connective tissue of the mucous 

 membrane is characterised by the large size of the vessels 

 composing it, their comparatively straight course, and nume- 

 rous anastomoses, whilst the arterial portion is greatly infe- 

 rior to the venous in the diameter of its constituent vessels, 



