LIPIDS PRESENT IN SKIN AND ITS APPENDAGES 



777 



Table 20 



The Lipid Composition of the Different Layers of the Skin 



of the Steer (Based upon Dry Weight)" 



Proportionate dry wt., 



% 3.0 6.2 12.7 7.3 58.7 12.1 



Total lipid 



% 4.60 8.72 7 28 1.95 2.44 7.15 



% skin lipid 3.39 13.4 22.8 3 52 35.6 21.4 



Cholesterol 



% 0.67 1.01 0.97 0.22 0.06 0.08 



% skin lipid 14.5 11.6 13.4 11.2 2.60 1.11 



Phospholipid^ 0.00 0.78 2.35 0.42 0.10 0.10 



Wax 



% 0.97 2.21 2.55 



% skin lipid 21.0 25.3 35.1 



Free fatty acids 



% 1.24 2.09 0.49 0.21 0.06 0.15 



% skin lipid 26 8 17.7 8.3 11.1 4.0 2.05 



a R. M. Koppenhoefer, ./. Biol. Chan., 116, 321-341 (1936). 



The lipid concentration is greatest toward the upper and lower extrem- 

 ities of the skin. In the epidermal region, cholesterol, phospholipids, and 

 waxes constitute the main lipids, while in the corium base a considerable 

 deposition of triglycerides obtains; this deposit is distinct from the sub- 

 cutaneous fat layer. 



a. Cholesterol and Other Sterols in the Skin. The greater proportion 

 of the skin cholesterol occurs in the epidermal region. 400,403-405 The 

 cholesterol present in the outer skin layers is largely in the form of esters, 

 while that in the corium consists principally of the free alcohol. Esteri- 

 fication of cholesterol is believed to take place concomitantly with the kera- 

 tinization of epidermal cells, which occurs only in the epidermal region. 



In the corium, the distribution of cholesterol is uniform, as is also that 

 of the phospholipids. This has led to the hypothesis that these lipid 

 constituents have a mutual physiologic relationship, and that they are 

 associated with cellular elements in the corium. The cholesterol concen- 

 tration begins to increase in the transition region, and reaches its maximum 

 in the epidermal portion of the skin. Although the phospholipid : chole- 



404 D. J. Kooyman, Arch. Dermatol, and Syphilol, 25, 444-450 (1932). 

 406 M. F. Engman and D. J. Kooyman, Arch. Dermatol, and Syphilol., 29, 12-19 

 (1934). 



