1388 



HUMAN ANATOMY. 



'a. 



Papillary 

 loops 



o 



U 



beneath the bases of the papillae. The latter are supplied by the terminal twigs which 

 ascend vertically from the subpapillary net-work and break up into capillary loops 

 that occupy the papillae and lie close beneath the epidermis (Fig. 1153). With the 

 exception of the loops entering the hair-papillae, the capillaries enclosing the hair- 

 follicles arise from the subpapillary plexus. 



The arrangement of the cutaneous veins, more complex than that of the arteries, 

 includes four plexuses (retia venosum) lying at different levels within the corium and 



extending parallel to the 



Fig. 1 153. . surfaces. The first and 



 ' ~ most superficial one is 



formed by the union of 

 the radicles returning the 

 blood from the papillae. 

 The component veins lie 

 below and parallel to the 

 rows of papillae and im- 

 mediately beneath the 

 bases of the latter. At 

 a slightly lower level, in 

 the deeper part of the 

 stratum papillare, the ve- 

 nous channels proceeding 

 from the subpapillary net- 

 work join to form a second 

 plexus with polygonal 

 meshes. A third occurs 

 about the middle of the 

 corium, while the fourth 

 shares the position of 

 the subcutaneous arterial 

 plexus at the junction of 

 the corium and subdermal 

 strata. The deepest plexus 

 receives many of the 

 radicles returning the 

 blood from the fat and 

 the sweat glands, the re- 

 mainder being tributary 

 to the veins accompany- 

 ing the larger arteries 

 as they traverse the tela 

 subcutanea. 



The lymphatics of 

 the skin are well repre- 

 sented by a close siiper- 

 ficial plexus within the 

 papillary stratum of the 

 corium into which the 

 terminal lymph-radicles of 

 the papillae empty. The 

 relation of these channels to the interfascicular connective tissue spaces is one only 

 of indirect communication, since the lymphatics are provided with fairly complete 

 endothelial walls. It is probable that the lymph-paths within the papillae are closely 

 related to the intercellular clefts of the epidermis, according to Unna, indeed, direct 

 communications existing. Migratory leucocytes often find their way into the cuticle 

 where they then appear as the irregularly stellate cells of Langerhans seen between 

 the epithelial elements. A wide-meshed deep plexus of lymphatics is formed within 

 the subdermal layer, from which the larger lymph -trunks pass along with the 

 subcutaneous blood-vessels. 



c 



CO 



3 



Section of kijected skin, showing general arrangement oi blood-vessels. X 40. 



